Vicon Nexus User Guide

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Vicon Nexus User Guide
Contents
About this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
About Vicon Nexus documentation . . . . . . . . . . . . . . . . . . . . . 5

Introducing Vicon Nexus . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Get to know Vicon Nexus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Vicon Nexus motion capture workflow . . . . . . . . . . . . . . . . . 29
Hot keys and shortcuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Prepare a Vicon system . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Configure Vicon hardware in Nexus . . . . . . . . . . . . . . . . . . . 44
Prepare a data storage location . . . . . . . . . . . . . . . . . . . . . . . 94

Calibrate a Vicon system . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Calibrate Vicon cameras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Set the volume origin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Calibrate the floor plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Manage camera calibrations . . . . . . . . . . . . . . . . . . . . . . . . . 105

Prepare a subject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Create a new subject from a template . . . . . . . . . . . . . . . . . 110

© Copyright 2016–2018 Vicon Motion Systems Limited. All rights reserved.
Vicon Motion Systems Limited reserves the right to make changes to information in this document without notice.
Companies, names, and data used in examples are fictitious unless otherwise noted. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic or mechanical, by
photocopying or recording, or otherwise without the prior written permission of Vicon Motion Systems Ltd.
Vicon® is a registered trademark of Oxford Metrics plc. Vicon Blade™, Vicon Control™, Vicon Lock™, Vicon Lock+™, Vicon
Nexus™, Vicon MX™, Vicon Pegasus™, Vicon ProCalc™, Vicon Shogun™, Vicon Studio™, T-Series™, Vicon Tracker™,
Vicon Vantage™, Vicon Vero™, Vicon Vertex™, and Vicon Vue™ are trademarks of Oxford Metrics plc.
VESA® is a registered trademark owned by VESA (www.vesa.org/about-vesa/). Other product and company names herein may
be the trademarks of their respective owners.
Vicon Motion Systems is an Oxford Metrics plc company. Email: support@vicon.com

Web: http://www.vicon.com

Calibrate a labeling skeleton . . . . . . . . . . . . . . . . . . . . . . . . . 113
Correcting swapped labels . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Manually label a trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Work with pipelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

Capture movement trials . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Capture the required movement . . . . . . . . . . . . . . . . . . . . . . 137
Reconstruct and label movement trials . . . . . . . . . . . . . . . . 150

Review trials and fill gaps . . . . . . . . . . . . . . . . . . . . . . . . . 152
Review processing history . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Review data quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Crop trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Fill gaps in trial data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
Add events to trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Modeling with Plug-in Gait . . . . . . . . . . . . . . . . . . . . . . . . 185
About the Plug-in Gait model . . . . . . . . . . . . . . . . . . . . . . . . 187
Plug-in Gait files installed with Vicon Nexus . . . . . . . . . . . 189
How Plug-in Gait works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Take subject measurements for Plug-in Gait . . . . . . . . . . . 191
Attach Plug-in Gait markers to a patient . . . . . . . . . . . . . . 199
Plug-in Gait Static pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Plug-in Gait Dynamic pipeline . . . . . . . . . . . . . . . . . . . . . . . . 203

Work with digital video files . . . . . . . . . . . . . . . . . . . . . . . 214
About transferring and transcoding . . . . . . . . . . . . . . . . . . . 215
Transfer and transcode digital video files . . . . . . . . . . . . . . 217

Web: http://www.vicon.com

De-interlace AVI files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

Work with IMUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Capture IMU data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
Manage your captured IMU data . . . . . . . . . . . . . . . . . . . . . 225
Transfer data from IMUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Export IMU data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Import data from the IMeasureU Research app . . . . . . . . 229
Calibrate IMUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
Pair an IMU to a different device . . . . . . . . . . . . . . . . . . . . . 232

Export trial data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
Configure file export pipeline operations . . . . . . . . . . . . . . 234
Export 3D workspace as AVI . . . . . . . . . . . . . . . . . . . . . . . . . 239

Further resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Web: http://www.vicon.com

Nexus
User
Guide

About this guide
This guide contains instructions for using Vicon Nexus. It explains configuring your
Vicon system within Nexus and the basic tasks that make up the everyday Nexus
workflow. It assumes you have already installed and licensed Nexus and set up your
Vicon system hardware. If you need information about these procedures, see Installing

and licensing Vicon Nexus and/or the Vicon documentation that was supplied with
your hardware, or for help with how to connect up your Vicon system, see Vicon system
setup information. You can also contact Vicon Support.
Videos of many of the procedures described in this guide, including many additional
tips and examples, are available from the Vicon Nexus 2 Tutorials playlist on YouTube,
beginning with system calibration.

Note
As the videos were recorded using an earlier version of Nexus 2, you may
notice small differences in the user interface.

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About Vicon Nexus documentation
The following documentation is available with Nexus, both as help pages available
online and as PDFs that you can download from docs.vicon.com:
Document

Description

What’s New
in Vicon
Nexus

Information about the main features that are new in the current

Installing
and
licensing
Vicon Nexus

Step-by-step instructions installing and licensing Nexus.

Vicon Nexus
User Guide
(this guide)

Information about how to use Nexus.

Vicon Nexus
Reference
Guide

Reference information about less frequently used or more complex

version of Nexus.

procedures, background information to provide you with a better
understanding of Nexus, and further details about the Nexus user
interface.

Creating
labeling
skeleton
templates
(VSTs)

Instructions on how to create your own custom labeling skeleton

Plug-in Gait
Reference
Guide

Detailed information on the Plug-in Gait model.

templates for use with Nexus.

For additional documentation related to Nexus and other Vicon documents, visit docs.
vicon.com.

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Regulatory information
For Vicon Nexus regulatory details, see Vicon Nexus regulatory information in the
Nexus documentation area of the Vicon website (docs.vicon.com).

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Introducing Vicon Nexus
The following topics will help you to become familiar with the basics of using Nexus:
Get to know Vicon Nexus on page 8
Vicon Nexus motion capture workflow on page 29
Hot keys and shortcuts on page 30

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Get to know Vicon Nexus
The Nexus user interface enables you to access the tools you need quickly and easily.
Within the primary panes (Resources, View, Tools, and Communications), you use the
tabs and buttons to open secondary panes containing tools and options for specific
parts of the motion capture workflow.

Resources pane: Manage the different components of your Vicon system, and
the subjects whose motion is to be captured, on the System tab and the
Subjects tab. See Manage system and subjects in the Resources pane on page
12.
View pane: Set up the way you want to visualize the capture data from one or
more cameras (or supported third-party devices) either live in real time or
offline, from a saved file. See Display data in the View pane on page 16.

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Tools pane: Work through the main stages of the motion capture workflow,
using the tabs in the Tools pane from left to right: System Preparation, Subject
Preparation, Capture, Label/Edit and Pipeline (this last tab enables you to
group and run operations that you use throughout the workflow). See Manage
the motion capture workflow in the Tools pane on page 18.
Communications pane: Store and manage all data associated with your motion
capture trials (Data Management tab: see Manage motion capture data with
the Data Management tab on page 11), assess trial health with the tools (
Quality tab: see Review data quality on page 154), view stored processing
history (History tab: see Review processing history on page 153), set up and
control monitors for your trials (Monitor tab), work with IMUs on page 222 (
IMeasureU tab), interact with MATLAB, view system status information ( Status
tab), and view a log of Nexus system activity since start up ( Log tab).
Menu bar: Access menu options. See Access menu options from the Nexus
menu bar on page 20.
Toolbar: Access frequently used commands and create and select view types.
See Access common commands from the Nexus toolbar on page 20.

Basic keyboard shortcuts and mouse actions
You can use the mouse to manipulate items and manage the way data is visualized in
Nexus, and you can combine standard mouse actions with keyboard keys. The following
mouse and keyboard combinations are used most frequently in Nexus.
Navigate in the 3D Perspective view:
Zoom: Right-click + drag forward or backward
Orbit: Click + drag
Translate/Move: Click wheel button (or left-and-right-click) + drag

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Tip
To open files in Nexus, in addition to loading files as described in Play back
data with the time bar on page 19, you can drag and drop Nexus files onto a
3D Perspective view (or any other view). File types that you can load in this
way include: C3D, ENF, VSK/VST, X1D, X2D, and XCP.

Select objects in the view pane:
Select a single item: Click
Select multiple consecutive items: SHIFT + click
Select multiple non-consecutive items: CTRL + click
Select items within a bounding outline: ALT + click and drag
Display/hide a section within a pane:
Click the Display Section arrow on the right

Click the Hide Section arrow on the right

For lists summarizing more Nexus shortcuts and mouse actions, see Hot keys and
shortcuts on page 30.

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Manage motion capture data with the Data Management tab
The Data Management tab of the Communications window enables you to create a
hierarchical structure in which to store and manage all the data associated with your
motion capture trials. For information on how to do this, see Prepare a data storage
location on page 94.

Tip
To toggle the display of the Data Management tab, press F2.

It also enables you to:
Assess trial health with the tools on the Quality tab. For more information, see
Review data quality on page 154.
View processing history on the History tab. For more information, see Review
processing history on page 153.
Set up and control monitors for your trials with the Monitor tab.
Interact with MATLAB.
View system status information on the Status tab.
View a log of Nexus system activity since start up on the Log tab.

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Manage system and subjects in the Resources pane
To manage Nexus system connection and real-time data-streaming, click the system
connection buttons at the top of the Resources pane:
Go Live: Connect the system and start real-time data streaming. The button's label
changes to Go Offline.

Go Offline: Disconnect the system and stop real-time data streaming. The button's
label changes to Go Live.

Pause: Pause real-time data streaming. When you click the Pause button while the
system is in Live mode, the button turns blue and a pause symbol

is displayed in

the view pane. When the system is in Offline mode, the button is unavailable.
At the top of the Resources pane, click the tab for the resources you want to manage:

System: View and configure Vicon system components
Subjects: Load and manage files for mocap subjects

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In the System Resources tree or Subjects Resources tree, select the item(s) you want
to configure.

Depending on whether you are in Live mode, you can then:
Right-click a node to display a context (shortcut) menu of commands that can be
applied to that item, if one exists.
In the Properties pane below the Resources tree, view the settings for the item(s)
selected in the tree. To view all of the available properties, click Show Advanced.

For more information, see Set properties in Vicon Nexus on page 14.

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Set properties in Vicon Nexus
You can configure certain aspects of the Nexus system, such as system components
and motion capture subjects, by configuring settings in the corresponding Properties
section of the user interface.
Required properties for which you must specify a value are indicated in the Nexus user
interface with a shaded background.
Some properties settings automatically persist, so Nexus remembers them in
subsequent sessions. You must explicitly save other settings using the relevant
configuration management controls for that area of the Nexus window.
To set properties in Nexus:
1. In the Nexus window, open the pane or dialog box containing the properties
whose settings you wish to configure. For example:
System components - System Resources pane
Motion-capture subjects - Subjects Resources pane
Camera calibration process - System Preparation Tools pane
Subject calibration process - Subject Preparation Tools pane
Data processing operations - PipelineTools pane
Monitor and event actions - Monitors tab in the Communications pane
Data visualization - Options dialog box
2. To view all of the available properties, click the Show Advanced link. To show
only the basic properties, click the Hide Advanced link.
3. View or change the setting for the desired properties using its entry field or
control.
4. When you are working in the following areas of the Nexus window, you can save
any changes you have made to the settings, using the configuration
management controls (indicated in the following images). Your settings are
saved to a configuration file, so that you can re-use them later.

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System Resources pane

Pipeline Tools pane

Monitors tab in the Communications pane

Options dialog box (press F7 to display)

Nexus toolbar (working with the layout of the view panes)

For more information on configuration files, see Manage configurations in Vicon Nexus
on page 21.

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Display data in the View pane
At the left of the View pane toolbar, click the drop-down list and select one of the
available views:

3D Perspective: Display 3D reconstructions of Vicon camera data.
3D Orthogonal: Orthogonal views of 3D data: -Z, +Z, +X, -X, +Y, or -Y

Note

RGB = XYZ

Camera: Display 2D optical data from Vicon cameras or video streams from
connected video cameras.
Graph: Display variables (model outputs), or system components such as force plate
or EMG activity.
Subject Viewer: Display the base (default) pose for the labeling skeleton template
(VST) of the currently selected subject. This is useful when you are calibrating and
manually labeling a labeling skeleton, which are explained in Prepare a subject on
page 108.

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At the right of the View pane toolbar, click the buttons to specify the number and
arrangement of views displayed:

Horizontal
Vertical
Close
Depending on the view selected, additional lists and buttons are available to manage
the display options.

Tip
To display multiple Camera views, in the System Resources tree, SHIFT+click
to select multiple cameras and in the View workspace, select Camera view.

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Manage the motion capture workflow in the Tools pane
At the top of the Tools pane, click the buttons for tools relating to the stage in the
workflow that you want to display. The buttons are displayed in the order of a typical
Nexus workflow (from left to right) and are enabled appropriately, depending on
whether you are in Live or Offline mode (the following image is in Live mode).

System Preparation: Prepare your Vicon system for motion capture.
Subject Preparation: Prepare subjects whose motion is to be captured.
Capture: Collect motion data.
Label/Edit: Label and fill any gaps in trial data.
Pipeline: Create and manage sequences of operations to process trials.
To find out more about the motion capture workflow, see Vicon Nexus motion capture
workflow on page 29.

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Play back data with the time bar
To explore the time bar:
1. Ensure a 3D Perspective view is displayed (see Display data in the View pane on
page 16).
2. On the Data Management tab at the bottom of the Nexus window, navigate to
an existing database. You can do this by expanding the displayed hierarchy and
using the Go forward to the next node, Go back to the last node, and Move up
one folder level buttons

3. In the Name column, double-click the trial that you want to load.
The Data Management window is minimized and Nexus opens the trial.
4. On the time bar, click the Play button or drag the current time indicator (blue
vertical line) to play back offline capture data. To crop a trial (restrict playback to
a range of frames), you can drag the Start and End Range indicators (the blue
triangles at the top of the timeline) along the time bar.

5. To re-display the Data Management window, double-click the Data Management
tab at the bottom of the Nexus window.

Tip
In addition to using the time bar to view and navigate trials, you can also use it
to:
View data quality as a heat map. For more information, see Review trial data
using the time bar on page 154.
Create and manage events (for example, a foot striking a force plate, or a
joint attaining a specified angle, etc). For more information, see Add events
to trials on page 180.

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Access menu options from the Nexus menu bar
The Nexus menu bar enables you to access common commands.

Access common commands from the Nexus toolbar
Access frequently used commands from the Nexus motion capture workflow from the
Nexus toolbar.

The Nexus toolbar contains buttons that enable you to save the current trial, close the
current trial, and undo and redo actions. In addition it contains the following controls:
Reconstruct Runs the Reconstruct pipeline defined in the Pipeline Tools pane.
(Reconstruction is the process by which Nexus calculates the position of markers in
three-dimensional space and links these points frame-by-frame into a trajectory.) For
examples of using this pipeline, see Calibrate a labeling skeleton on page 113.
Reconstruct and Label Runs the Reconstruct and Label pipeline defined in the
Pipeline Tools pane. (The Label process is where labels defined in the labeling
skeleton template for the subject are applied, either manually or automatically, to a
point in the trajectory of a marker.) Normally used when processing trials. For an
example of using this pipeline, see Reconstruct and label movement trials on page
150 .
KinFit Runs the Kinematic Fit pipeline defined in the Pipeline Tools pane. This
pipeline is often used before running a Fill Gaps - Kinematic operation for filling gaps
in trajectories, and for visualizing or graphing segment- or joint-based data in
realtime.
AutoInitialize Runs the Auto Initialize Labeling pipeline defined in the
Pipeline Tools pane. Often used as part of calibrating a labeling skeleton For an
example of using this pipeline, see Calibrate a labeling skeleton on page 113.

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Auto Gap Fill Runs the Auto Intelligent Gap Fill pipeline defined in the
Pipeline Tools pane. This enables you to quickly fill gaps in your trial, without having
to choose which fill method is best for each gap. For good results, you must
configure the relevant pipeline operations for your particular trials. For information
on using this command, see Automatically fill gaps in trial data on page 177.
Add To Quick Report Adds the current trial to a Quick Report. For more
information, see Quick Reports in the Vicon Nexus Reference Guide.
Any user-customized buttons If required, you can create your own additional buttons
and configure them to run a specified pipeline or load a previously created view
configuration. You can create or change toolbar buttons in the Customize Toolbar
dialog box.
View Type list Lists any saved view types. The adjacent
configuration buttons enable you to create

and save

custom view types.

Clicking a button on the toolbar executes the defined action for the button. A button is
dimmed if it is not available, for example, if it cannot be run at that stage of the
workflow or if a customized button has been deleted or renamed.

Tip
To display a tooltip that explains why a button is unavailable, hover the mouse
pointer over the button.

Manage configurations in Vicon Nexus
You can determine how Nexus looks and behaves by creating and editing
configurations in the configuration management controls in the Nexus window. To
view and select any default configurations that were installed with Nexus, click the
dropdown list in the relevant configuration management controls, for example, for View
Types:

You can create different configurations to suit different types of motion capture
applications and then select the appropriate configuration when required. You can also
save configurations for use by multiple users (Shared) or for a specific user (Private), to
suit the way your organization works:

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Shared These configurations can be viewed by all users; they can be changed only by
the user who was logged on when the file was first created and saved. Shared
configuration files are stored in the appropriate folder, by default under:
C:\Users\Public\Documents\Vicon\Nexus2.x\Configurations
Private These configurations can be viewed and changed only by the user who was
logged on when the file was first created and saved. Private files are stored in the
appropriate folder under the logged-in user's Application Data files folder, by default
under:
C:\Users\\AppData\Roaming\Vicon\Nexus2.x\Configurations\
System These configurations are the default configurations that are installed with
Nexus and are stored in the Nexus configurations folder, by default:
C:\Program Files (x86)\Vicon\Nexus2.#\Configurations
For more information, see Recognize Shared, Private, and System files on page 25.

Important
The default Nexus toolbar is stored in the Standard.toolbar configuration file
in the Shared Nexus configuration folder Toolbars. If you add, delete, or
reposition buttons on the Nexus toolbar using the Customize Toolbar dialog
box, these customizations are stored in your Private configuration folder.

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To manage configurations in Nexus:
1. In the Nexus window, open the pane or dialog box containing the type of Nexus
configuration file you want to manage:
Nexus UI area

Configuration type

Configurations
folder\file

Capture Tools pane

Motion capture

TrialTypes\*.

settings

TrialTypes

Biomechanics Workflow area of

Biomechanics

CaptureWorkflows\*.

Communications pane

workflow

CaptureWorkflow

Sounds dialog box

Sounds settings

AudioSchemes\*.
AudioScheme

Monitors tab in Communications

Event monitors

pane

and actions

Monitors\*.Monitors

Options dialog box

Data view options

Options\*.Options

Pipeline Tools pane

Automated

Pipelines\*.Pipeline

processing
operations
System Resources pane

System settings

Systems\*.System

Toolbar

Toolbar buttons

Toolbars\*.Toolbar
(see note above)

View pane

Vicon Motion Systems Ltd.

View options and

ViewTypes\*.

layouts

ViewType

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2. Depending on whether you want to create a new configuration from scratch or
change the current configuration or either:
Leave the currently loaded configuration file. (If no configuration file has been
created yet, Untitled* is displayed and no other options are available.)
or
Select another configuration file from the dropdown list. If you have made
changes to the current configuration file, Nexus prompts you to save these
before changing the configuration file.
3. In other areas of the Nexus pane or dialog box, make any desired changes to
settings, such as those in a Properties section.
4. Click the configuration menu button

and select the required command from

the displayed list:
New: Create a new configuration in which to save the current settings. The
name Untitled* is displayed in the Choose configuration list.
Save As: In the Save As dialog box, enter a name to overwrite the default new
configuration file name Untitled* or to create a new system configuration file
in which to save a copy of the current configuration file and click OK.
Additional options include:
Rename: In the Rename dialog box, enter a new name for the currently loaded
configuration file and click OK.
Delete: At the Delete prompt, click Yes to delete the current file displayed in
the configuration dropdown list.
Mark Read-Only: Select to protect the current configuration file from further
changes.
Set Defaults: Returns values to their default settings.
Import: Enables you to select and import a configuration file. This is useful
when you want to copy a configuration file from another machine.
Reload: Reload or delete an automatically saved configuration file. You can
select from the list of timestamped files or, if required, delete all the saved
configurations.
Refresh List: Re-display the contents of the configuration dropdown list. This
is useful if you copy a file into one of the Configurations sub-folders, enabling
you to update the options displayed in the relevant list, without having to restart Nexus.

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5. In the Configuration type dialog box, select the user permissions for the
configuration: Shared or Private.
The new file name is displayed in the configuration dropdown list.
6. Click the Save button to store the settings in the configuration displayed in the
configuration dropdown list.

For more information, see Set properties in Vicon Nexus on page 14.

Recognize Shared, Private, and System files
When pipelines, view types, monitors, labeling skeleton templates, and configurations
are displayed in Nexus (ie, listed in menus, etc), you can immediately recognize whether
they are Private, Shared, or System files:
Icon

File

Description

type
Shared

Can be viewed by multiple users; can be changed only by the user
who was logged on when the file was first created and saved.
Shared files are stored in subfolders in:
C:\Users\Public\Documents\Vicon\Nexus2.x

Private

Can be viewed and changed only by the user who was logged on
when the file was first created and saved. Private files are stored
in subfolders in:
C:\Users\\AppData\Roaming\Vicon\Nexus2.x

System

Cannot be changed (Read-Only) and are upgraded when the next
version of Nexus is installed. Stored in subfolders in the Nexus
installation folder, whose default location is:
C:\Program Files (x86)\Vicon)\Nexus2.# or
C:\Program Files\Vicon\Nexus2.#

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Customize the Vicon Nexus user interface
In addition to the usual resize and close window options, you can slide the Resources
and Tools panes to either side of the Vicon Nexus window and or minimize the
Communications pane, to give you a larger workspace area.

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Requirement

Action

To hide the

At the top of the Resources or Tools pane, click

Resources and

the UnPin button.

/or Tools panes

To hide the

Double-click a tab within the Communications

Communications

pane; or

pane

To hide the pane whenever you load a trial, on
the Window menu, select the Close
Communications Pane on Trial Load option.

To reveal the

Click the tab at the side of the Nexus window

Resources and
/or Tools panes

To reveal the

Double-click a tab within the Communications

Communications

pane; or

pane

To make the pane visible whenever you load a
trial, on the Window menu, clear the Close
Communications Pane on Trial Load option.

To return a pane

At the top of the pane, click the Pin button.

to being locked
into place
To undock (float)

At the top of the (pinned) pane, click the Undock

and dock a pane

or Dock button.
or

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Customize a View pane
The View pane cannot be undocked, repositioned, or resized in the Nexus window.
However, you can open a separate floating view pane by selecting the New floating
workspace command from the Window menu. This floating workspace can be
repositioned and resized.
The width of the View pane is affected by resizing panes to the left and/or right of it.
The height of the View pane is affected by resizing the panes below it.

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Vicon Nexus motion capture workflow
In Vicon Nexus, you can capture and analyze the movement of live subjects (such as
human beings or animals) and of inanimate objects (such as sports equipment or other
rigid objects) for a variety of motion capture applications. You can either stream motion
data in real time or capture it for offline processing, depending on your requirements.
The stages involved in the typical workflow for the operation of Nexus for motion
capture production and control are outlined below.
Prepare a Vicon system on page 43 when you first set up or significantly change
your motion capture system.
Calibrate a Vicon system on page 96 when you first set up your system and
regularly afterwards (eg, at the start of every day, before you begin motion capture),
to ensure any changes (eg, slight movement of cameras or other equipment) is
accounted for. You also do this if you make changes to the system.
Prepare a subject on page 108 when you have a new subject, or want to make
changes to an existing subject. This stage includes calibrating a labeling skeleton for
your new subject or re-calibrating when you have made changes to an existing
subject.
Capture movement trials on page 136 after you have calibrated the labeling skeleton,
to collect the data needed for your trials.
Review trials and fill gaps on page 152 after you have captured, reconstructed and
labeled your movement trials, to fill any gaps in the data.
After you have filled any gaps and cropped the data as necessary, you can perform
any required modeling (for example, you can run the dynamic Plug-in Gait model, or
perform custom modeling) to generate the required model outputs (such as angles,
forces, moments, powers, or bones). For information, see Modeling with Plug-in Gait
on page 185.
Export trial data on page 233, which is normally the final stage in motion capture,
and enables you to use the captured data in third-party applications.
To speed up some of the above processes, you can use the supplied pipelines,
consisting of one or more operations that are supplied with Nexus, or you can create
your own custom pipelines. To use pipelines on a large number of trials, you can run
them as batch processes. For more information, see Work with pipelines on page 131.

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Hot keys and shortcuts
To help you use Vicon Nexus efficiently, this section provides lists of shortcuts:
Common hot keys and shortcuts on page 30
Shortcuts for navigating in Vicon Nexus on page 32
Shortcuts for managing real-time data on page 33
Shortcuts for selecting items on page 34
Shortcuts for moving the camera view on page 35
Shortcuts for viewing data in 3D views on page 35
Shortcuts for viewing data in the Graph view on page 36
Shortcuts for visualizing graph data on page 37
Shortcuts for working with the time bar on page 38
Shortcuts for gap-filling on page 41
Shortcuts for using the Quality tab on page 42

Common hot keys and shortcuts
You can use the mouse to manipulate items and manage the way data is displayed in
the Vicon Nexus window. Standard mouse actions can also be combined with keyboard
keys. The following mouse actions and hot keys are available throughout Nexus, where
applicable/available:
Task

Keys and mouse

Start/stop capture

CTRL+Enter

Select individual items

Click

Select items within a bounding outline

ALT+click and drag

Select multiple non-consecutive items

CTRL+click

Rotate/orbit

Click and drag

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Task

Keys and mouse

Zoom

Right-click and drag

Translate/Move

Click wheel button (or
left-and-right-click) and
drag

Scroll forward or backward through a list

Rotate mouse wheel

Undo

CTRL+Z

Redo

CTRL+Y

Save currently enabled subject data to the current trial's

CTRL+S

.c3d file (equivalent of clicking Save on the File menu)
Reset Core Processor

CTRL+R

Esc

Exit current mode
(labeling, etc)

Unset all cameras' Bumped status

CTRL+SHIFT+B

Note
The behavior of the ALT GR key depends upon the regional settings specified
for your keyboard in the Windows operating system. In some regions, the
behavior of this key is identical to that of the ALT key, while in other regions
the ALT GR key functions as if the ALT+CTRL keys were pressed together.
Nexus assumes the latter behavior.
If you wish to use the ALT GR key as if it was the ALT key, you must change
the regional settings for your keyboard to use the US layout, which assumes
identical behavior for these two keys. You change your keyboard language
settings in the Text Services and Input Languages dialog box, accessed from
the Languages tab in the Regional and Language Options dialog box in
Windows Control Panel. For more information, see the Microsoft Windows
help.

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Shortcuts for navigating in Vicon Nexus
Use the following hot keys to navigate to the different areas of the Vicon Nexus user
interface.
Task

Keys

Display the Vicon Nexus online help

Display/Close Data Management tab

Display/Close the Quick Reportswindow

Enter/Exit full screen mode

Display/Close Sounds dialog box

Display/Close Options dialog box

Go to System Preparation Tools pane

Go to Subject Preparation Tools pane

Go to Capture Tools pane

F10

Go to Label/Edit Tools pane

F11

Go to Pipeline Tools pane

F12

The behavior of function keys is dependent upon the area of the Nexus window that
has focus when the key is pressed. Click anywhere in the window to set the focus
before using the function keys to navigate to a different part of the user interface.

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Shortcuts for managing real-time data
Use the following hot keys to manage real-time data streaming and offline data
processing in Vicon Nexus.
Task

Keys

Start/stop capture

CTRL+Enter

Switch between Live and Offline mode

CTRL+TAB

Pause/Restart real-time data streaming (Live

SPACE (or middle mouse

mode)

button)

Play/Stop offline data (Offline mode)

SPACE (or middle mouse
button)

Toggle Simple Capture mode (Live mode)

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Shortcuts for selecting items
Use these hot keys and mouse actions to select items in the Vicon Nexus window. To
cancel a selection, left-click again in the view pane.
Task

Keys and mouse

Select single item

Click

Select multiple non-consecutive items

CTRL+click

Select multiple non-consecutive items maintaining

SHIFT+CTRL+click

the order of selection
Select multiple consecutive items

SHIFT+click, SHIFT and
drag, or drag

Select next optical camera

]

Select previous optical camera

[

Select next video camera

CTRL+]

Select previous video camera

CTRL+[

In a Camera view, sweep select for manual masking

ALT+drag

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Shortcuts for moving the camera view
Use the following mouse actions to move the camera view in the 3D Perspective, 3D
Orthogonal, and Camera views.
Task

Keys and mouse

Zoom: Move the camera viewpoint closer to or

Right-click + drag forward or

further away from the focal point

backward

Orbit: Move the 3D viewpoint around the focal

Left-click + drag left, right,

point

forward, or backward

Translate: Move the 3D viewpoint along a

Click wheel button + drag left,

horizontal or vertical axis

right, forward, or backward

Zoom to window (for all windows). Applies in

CTRL+SHIFT+Z

Camera, 3D Overlay and Rotated views.
Zoom camera view to fit

CTRL+SHIFT+F

Shortcuts for viewing data in 3D views
Use the following hot keys to view data in the 3D Perspective and 3D Orthogonal views:
Task

Keys

Toggle display of labels

CTRL+space
bar

Reset footstrike counters (see Automatically assess foot strikes on

CTRL+SHIFT+R

page 146 ).

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Shortcuts for viewing data in the Graph view
Use the following hot keys and mouse actions to view data in the Graph view. For more
information, see Shortcuts for visualizing graph data on page 37.
Task

Keys and mouse

Select range of frames to zoom

ALT and right-click + drag across frames

Slide x-axis left

Click wheel button + drag left

Slide x-axis right

Click wheel button + drag right

Slide y-axis up

Click wheel button + drag forward

Slide y-axis down

Click wheel button + drag backward

Zoom x-axis in

Right-click + drag left

Zoom x-axis out

Right-click + drag right

Zoom y-axis in

Right-click + drag backward

Zoom y-axis out

Right-click + drag forward

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Shortcuts for visualizing graph data
The way the graph that is displayed in a Graph view depends on whether the system
connection is live or offline and whether an individual point or a range has been
selected for plotting.
When zooming into or out of graph data, the display of grid lines in the view pane can
be set to guide the eye toward the selected area of focus. Major grid lines remain at
their normal weight, while any minor grid lines gradually fade. To obtain this behavior,
open the Options dialog box (F7) and under General View Options, select Graph. In the
Properties pane on the right, ensure Show Minor Grid Lines is selected.

Zoom an axis (x or y)
All component graphs in a single workspace maintain the same scale for both the xand y-axes. The x-axis is shared across all components, but each component has its
own y-axis. The y-axes may show different ranges, but represent the same number of
values.
Offline: The portion of the specific component trace displayed in the view pane is
centered around the point where the mouse was clicked. All other component views
are scaled by the same amount, with the vertical range centered on the median value
of the visible portion of all the selected traces.
Live: The x-axis, the workspace is centered around zero, keeping zero on the right
edge of the workspace and changing the values displayed on the left.

Zoom selected range of frames
Offline: The y-axis displays only the selected area of the specific trace and the x-axis
displays only the selected frames.
Live: This type of zooming in the x-axis is disabled to ensure that the live frame is
always on the right of the graph.

Pan across an axis (x or y)
Offline: Each component in the y-axis can be panned independently.
Live: Panning in the x-axis is disabled to ensure that the live frame is always on the
right of the graph.

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Open a Quick Reports window
In addition to displaying a Graph view, you can also open a Quick Reports window
(press F4), which enables you to display multiple graphs of model outputs normalized
over the gait cycle. For more information, see Quick Reports in the Vicon Nexus

Reference Guide.

Shortcuts for working with the time bar
Use the following hot keys and mouse actions to work with the time bar at the bottom
of a view pane:

Timescale displayed in timeline
Task

Keys and mouse

Slide timeline left

Middle-click + drag left

Slide timeline right

Middle-click + drag right

Select range of frames to zoom

ALT and right-click + drag across frames

Zoom scale in

Right-click and drag right or up

Zoom scale out

Right-click and drag left or down

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Time bar data displayed in view pane
Task

Keys and mouse

Start/Stop data playback

Middle-click

Jog forward/backward through data playback

Rotate mouse wheel forward
/backward

Move Current Time Cursor to specific frame

Click frame in the timeline

Move Start Range Frame Cursor back to zero

Click cursor

frame of trial
Move End Range Frame Cursor back to last frame

Click cursor

of trial
Go to the previous frame

LEFT ARROW

Go to the next frame

RIGHT ARROW

Go to the first frame

HOME

Go to the last frame

END

Go forward 10 frames

PAGE UP

Go backward 10 frames

PAGE DOWN

Go to frame

CTRL+G

Set Region of Interest

CTRL+D

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Event identification mode in timeline
Task

Keys

Enter/exit event identification mode

CTRL+E

(where the time cursor follows the
mouse)
Go to the previous event

CTRL+LEFT ARROW

Go to the next event

CTRL+RIGHT ARROW

Lock/unlock event context (In event

UP ARROW or DOWN ARROW

identification mode, select desired Left,
Right, or General event context on
timeline; subsequently moving the
mouse forward or backward does not
change context.)
Display context menu (after event

ENTER

context locked)
Highlight command from context menu

UP ARROW or DOWN ARROW

Select highlighted command from

ENTER

context menu
Move event to next frame

ALT+RIGHT ARROW

Move event to previous frame

ALT+LEFT ARROW

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Shortcuts for gap-filling
Use the following hot keys to speed up gap-filling and correcting swapped marker
labels:
Task

Keys

Select next gap

CTRL+8

Select previous gap

CTRL+7

Spline fill

CTRL+U

Spline fill all

CTRL+I

Pick source for pattern filling

CTRL+9

Pattern fill

CTRL+O

Pattern fill all

CTRL+P

Pick source for rigid body fill

CTRL+J

Rigid body fill

CTRL+M

Rigid body fill all

CTRL+,

Pick segment for kinematic fill

CTRL+K

Kinematic fill

CTRL+L

Kinematic fill all

CTRL+.

Cyclic fill

CTRL+;

Cyclic fill all

CTRL+'

Swap marker labels

CTRL+T

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Shortcuts for using the Quality tab
Use the following hot keys to speed up working on the Quality tab, when using the
Data Correction view type:
Task

Keys

Show/hide unlabeled trajectories

CTRL+F3

Show/hide trajectory names

CTRL+F4

Move to next gap for selected trajectory

CTRL+8

Move to previous gap for selected trajectory

CTRL+7

Move to previous trajectory

CTRL+PgUp

Move to next trajectory

CTRL+PgDown

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Prepare a Vicon system
Before you can use your Vicon Nexus system, you need to configure the system for
motion capture.
When you have done this, the next step is to prepare a hierarchy of folders in which to
store all the files associated with your motion capture trials.
These procedures are explained in the following topics:
Configure Vicon hardware in Nexus on page 44
Prepare a data storage location on page 94
Before you begin to configure your Vicon system, ensure that the following
prerequisites have been met:
It is assumed that your Vicon system hardware (including the Vicon cameras, Vicon
connectivity units, and any supported third-party devices) has been set up and
connected and that Nexus has been installed and licensed. Your Vicon system may
have been professionally installed by a Vicon Support engineer. If you are installing
the system yourself, for full details on installing system hardware, see the Vicon
documentation that was supplied with your hardware, and for installing and licensing
the software, see Installing and licensing Vicon Nexus.
Vicon Nexus software is licensed using Safenet licensing and the VAULT licensing
system. The licensing drivers must have been installed on the host PC, and the
dongle must be plugged into an appropriate port (parallel or USB) on the computer
while you are running the application software.
The IP address for the Ethernet card on the host PC must be set to 192.168.10.1 using
the default IP address range (for details, see the Vicon PDF PC Setup for Vicon

Systems, which can be downloaded from the Vicon documentation website).

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Configure Vicon hardware in Nexus
The first time you use your Vicon Nexus system, you must configure the Vicon cameras,
connectivity units, and any supported third-party devices such as digital video cameras,
force plates, or EMG devices. After this, you only need to change the system setup in
Nexus if you change your hardware configuration or if you need different system
settings, for example, a different camera frequency.
You can save your system settings in a configuration file so that you can re-use or
modify them later. You can create any number of system configuration files. You can
then load the appropriate file for a particular type of motion capture application. For
more information, see Manage configurations in Vicon Nexus on page 21.
When you start Nexus, it automatically detects all the hardware currently connected to
your Vicon system, and groups them into several different categories. You configure
the Vicon system hardware and system-wide parameter and data processing settings
on the System tab in the Resources pane (referred to as the System Resources pane).
Basic setup information for each type of hardware that is likely to be present in a Vicon
Nexus system is included in the following topics:
Connect devices running the Vicon Control app on page 49
Configure system settings on page 52
Configure Vicon optical cameras for data capture on page 55
Configure video cameras for digital video capture on page 61
Aim Vicon cameras on page 64
Mask unwanted reflections on page 66
Configure Vicon connectivity units on page 70
Configure supported devices on page 74
If your system contains more than one Vicon Lock+ or MX Giganet, or if you want to
change the automatically assigned synchronization master, also see Change the
synchronization master on page 45.
If you are not sure whether your firmware is up-to-date or if you have received an email
from Vicon Support about updating your firmware, see the instructions on how to
Update firmware on page 46.

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Change the synchronization master
The node for the device designated as the Vicon system synchronization master, which
is responsible for providing the master synchronization signal to the system, is
highlighted in bold in the System Resources tree. Depending on the age of your Vicon
system and the connectivity devices it includes, Vicon Nexus automatically designates
the synchronization master:
If a Vicon Lock+ or an MX Giganet is included in the system, it is automatically
designated as the synchronization master.
If the system does not contain a Lock+ or an MX Giganet, then a Vicon camera is
automatically designated as the synchronization master.
If the system contains more than one Lock+ or MX Giganet, you must ensure that the
connectivity unit that is connected to the PC (known as the primary unit) is the
synchronization master. However, because Vicon software cannot detect which
connectivity unit is connected to the PC, you may need to change the automatically
selected master.
To change the synchronization master:
1. At the top of the System tab, click Local Vicon System to select it.
2. At the top of the Properties pane, click Show Advanced.
3. In the System section of the Properties pane, click the Preferred Master list and
then choose the required synchronization master from the list.

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Update firmware
Each Vicon camera and connectivity unit is programmed with firmware to control its
operation. Periodically, Vicon supplies firmware updates to correct or improve device
functionality. You apply these firmware updates to your Vicon devices via the Vicon
Ethernet network using the Vicon Firmware Update Utility, as described below.
For versions of Nexus 2.8 and later, you are automatically notified when any
component of your Vicon system is running out-of-date firmware, and given the
opportunity to update to the latest version. (For information about updating firmware
for earlier versions of Nexus, see the earlier Nexus documentation.)

Important
To ensure optimum performance and access to all the latest functionality,
Vicon recommends that you upgrade to the latest firmware whenever it
becomes available.

To monitor and/or upgrade system firmware:
1. When you start Nexus or connect any Vicon devices into your system, Nexus
checks to see whether the firmware for all your devices is up-to-date.
If your devices aren’t using the latest firmware, Nexus displays an icon in the
toolbar to let you know that a more up-to-date version of the firmware is
available:

2. Click on the icon to display more information.
Nexus displays a prompt that enables you to open the Vicon Firmware Update
Utility (reprogramming tool).

3.
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3. Click Yes to open the Vicon Firmware Update Utility. Note that you can also open
the Vicon Firmware Update Utility from the Start menu (select Vicon > Vicon
Firmware Update Utility).
Nexus closes and the Vicon Firmware Update Utility is displayed, showing all the
connected devices and their current firmware version.
By default, all devices are selected.

4. If you don’t want to update any of the devices, clear the relevant check box(es).
Note that if required, you can select devices to be updated that are already using
the latest version.
5. At the bottom of the Vicon Firmware Update Utility window, in the Choose
Firmware version list, select or browse to the required firmware version.
6. Click Reprogram to update the firmware for the selected device(s).

When updating is complete, the Firmware Version column displays the updated
firmware version and the System Status line and the Reprogramming Status
column display Complete on a green background.

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Note
If you do not have continual internet access, Nexus is unable to notify you
when a new version of the system firmware is available. In this case, install the
Vicon Firmware Update Utility on an internet-connected machine to detect
and download the latest version of the firmware. You can then transfer this
download to the local machine and use the Vicon Firmware Update Utility to
update to the latest version of the firmware.

To downgrade to an earlier firmware version
To downgrade to a firmware version that was previously downloaded, open the Vicon
Firmware Update Utility (from the Start menu click Vicon > Vicon Firmware Update
Utility) and select the required firmware version.

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Connect devices running the Vicon Control app
To make it easy for a single operator to set up Vicon cameras, you can use the Vicon
Control app, which runs on compatible iOS and Android devices. For more information,
see the Vicon Control app on the Vicon website. If you are using the Vicon Control app,
connect it to your Vicon Nexus system so that you can use it to configure Vicon
cameras.
The following procedure describes how to connect Vicon Control to your Vicon Nexus
system.
Before you can use your phone or tablet with Nexus, you must pair it with the PC that is
running Nexus (the Vicon host PC).
To connect a device running the Vicon Control app to Nexus on a Vicon host PC:
1. Ensure that your device is connected to a Wifi access point that is on the same
subnet as the Vicon host PC.
2. On the Vicon host PC, ensure that the required connection is used, that Nexus is
running, and the system is connected.

3. On the device, open the Vicon Control app.

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The connection to Nexus is displayed on the initial Control screen:

4. Tap the Nexus icon.
You are alerted that you must authorize the connection on the Vicon host PC
before you can continue.
In Nexus on the Vicon host PC, an authorization request is displayed:

5. To use the same connection in future, select Remember this choice for future
connection attempts. To permit Control to access Nexus, click Allow.

Tip
If later you need to revoke authorizations for Vicon Control, either rightclick the node for the device in the System Resources tree and then
click Revoke Authorization, or on the Window menu in Nexus, click
Manage Control Authorizations and click Forget Device (for a single
device) or Forget All (for all connected devices).

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On the device, a screen similar to the following is displayed:

6. To select a camera and display a camera view, tap at the bottom of the screen.
You can swipe the camera view right or left to change to the next or previous
camera and use stretch and pinch as normal to zoom in and out.
To access the dial control, tap and hold in a selected camera view.

7. Use the dial to view and change settings, calibrate and capture.

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Configure system settings
You specify system-wide settings in the System Resources pane, by clicking on the toplevel node called Local Vicon System. This node is displayed when Nexus is in Live
mode (if necessary, click the Go Live button to see this node). It contains sub-nodes for
each device connected to your Vicon system.

If you have saved any system configurations (.system files), before changing Local
Vicon System settings, ensure the required configuration is selected at the top of the
System Resources pane (see Manage configurations in Vicon Nexus on page 21).
The Local Vicon System node provides access to system-wide properties, enabling you
to:
Configure the Vicon system capture rate and the amount of memory allocated to
Nexus for motion capture.
Manage the way Nexus produces real-time 3D representations of the subjects whose
motion is being captured.
Specify the identification and connection settings for the Nexus host PC.
Specify video standards and timecode options.

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To change Vicon system settings:
1. If Nexus is currently offline, in the Resources pane, click Go Live.
2. On the System tab, click the Local Vicon System node.
3. In the Properties pane at the bottom of the System tab, view or change settings
for the required properties to suit the needs of your motion capture application.
When you set up your Vicon system, ensure that the Requested Frame Rate
property in the System section of the Properties pane is suitable for your
application.
The Requested Frame Rate is the rate (in Hz) at which to synchronize the Vicon
cameras. If you are using an external video signal, select from displayed values
(multiples of the base frame rate of the PAL, NTSC, or Film video standard
specified in Standard) up to a maximum of 2,000. You can choose any number
you want if you do not have any Genlock Standard set.

Tip
The default setting of 100 (Hz) is suitable for a range of common
applications, so unless you have a specific requirement for a different
value, you do not need to adjust this setting.

You can configure additional properties as required to suit your motion capture
application. To view all the available properties for Local Vicon System, at the top
right of the Properties pane, click Show Advanced.

For detailed information about each of the properties, see Local Vicon System

properties in the Vicon Nexus Reference Guide.

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When you have finished specifying the properties, at the top of the System tab,
click the Save button to save your system configuration settings to a .system file
in the Systems configurations folder (see Manage configurations in Vicon Nexus
on page 21).

Tip
The node for the device designated as the Vicon system synchronization
master is highlighted in bold in the System Resources tree. For information on
changing the synchronization master, see Change the synchronization master
on page 45.

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Configure Vicon optical cameras for data capture
As part of setting up your Vicon system, you must specify the required settings for
Vicon optical cameras. To do this, you use the Vicon Cameras node in the System
Resources pane. You can configure the settings for an individual camera, several
cameras, or all cameras at once.

The Vicon Cameras node is displayed under the Local Vicon System node when Vicon
Nexus is connected to a Vicon system and is in Live mode. It is displayed under the
Vicon Data node when Nexus is in Offline mode. It lists each Vicon optical camera
connected to your Vicon system. For each camera, the node name includes the device
position number, any display name specified in the Identification property, and the
camera type in parentheses, for example, #1 Over Door (Vantage 16).

Important
Before making changes to your Vicon camera settings, ensure that:
You have set your cameras' focus and aperture. (

To see

how to set up Vicon Vero cameras with Vicon Tracker software, which is
similar to Nexus setup, see the Tracker Installation and Training Guide on
YouTube.)
The required system configuration has been selected in the System
Resources pane (see Manage configurations in Vicon Nexus on page 21).
Your calibration device (wand) is available.
You have some markers with which to outline the capture volume. This will
also assist with camera setup.

If you are setting up a mixed camera system (that is, a system that includes both Vicon
MX T-Series cameras as well as other current Vicon cameras), see also Set up mixed
Vicon camera systems on page 59.

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To configure Vicon optical cameras for data capture:
1. Ensure Vicon Nexus is in Live mode. If it is not, in the Resources pane, click Go
Live.
2. To visualize your capture volume, from the view pane menu, select Camera.

3. In the System Resources tree, select the node(s) for the camera(s) whose
properties you wish to configure, either:
Vicon Cameras node for all Vicon cameras
or
A sub node for a specific Vicon camera. The camera sub-nodes on the System
tab correspond to the Names you set in the Properties pane (see below).
Note that If no Lock+ or MX Giganet is present in the Vicon system, the subnode for the Vicon camera acting as the synchronization master is displayed in
bold.
When a camera is selected, a blue status light on its strobe unit lights up.

Tip
In many cases, it is best to start by selecting all of the cameras, to find a
common baseline. You can then adjust individual cameras as required.

4. In the capture volume, have someone wave the calibration wand and ensure that
you can see marker images moving in the Camera view.

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5. In the Properties pane at the bottom of the System tab, click Show Advanced to
show additional properties.
When you first set up your Vicon system, configure the following camera
properties in the order shown. (If you are not sure what a particular setting
means, you can display a tooltip by hovering the mouse over the relevant field or
control ):
Identification section:
Name (If you wish to distinguish it from the other cameras)
Settings section:
Strobe Intensity In most cases, keep its default setting (1). However, if your
Vicon system consists of a mix of MX T-Series cameras and other current Vicon
cameras, and if it is crucial to your work that the shutter periods for all are
precisely aligned, ensure that your firmware is upgraded to version 700 or later,
and set the Strobe Intensity for the T-Series camera(s) to the maximum. For
more information, see Set up mixed Vicon camera systems on page 59.
Gain Only adjust this setting if the markers appear too faint or the cameras
have trouble distinguishing them; otherwise, leave at its default setting (x1).
Vicon does not recommend using a setting higher than x2.
Grayscale Mode This setting determines what data is sent from the camera to
the computer. Ensure this is set to the default setting ( Auto) for capturing
data. If the camera recognizes a blob as a circle, only centroid data is sent. If
the camera cannot distinguish the blob as a circle, full grayscale data is sent so
that Nexus can attempt to circle-fit the blobs. Circle fitted markers are
displayed as crosshairs in the Camera view.
Centroid Fitting section:
Threshold This setting differentiates between markers and ambient light. A
value in the region of 0.2 (the default) to 0.5 is usually appropriate, but Vicon
strongly recommends that you view static markers in the volume to establish
an appropriate setting. If cameras are evenly spaced around the volume, the
same Threshold value is usually sufficient for all cameras.
Minimum Circularity Ratio The circularity threshold used by the centroid-fitting
algorithms in a Vicon camera to fit centroids to grayscale blobs. The higher the
value, the more stringent the centroid fitter is. For camera calibration, you may
wish to apply higher settings to ensure that the Vicon system selects the best
markers and thus provides the best possible calibration. For data capture, a
lower value may be appropriate. When a blob is fitted with a centroid, it is
represented by crosshairs. The default setting is 0.5.

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Tip
If adjusting these settings does not easily enable you to eliminate
reflections, create camera masks to eliminate reflections and other
unwanted light sources that occur in parts of the capture volume. For
information on masking, see Mask unwanted reflections on page 66.

Centroid Tracking section:
Enable Centroid Tracking Tracking 2D camera centroids provides extra
information that maintains marker labels in real time when only one camera
can see a marker. When enabled, the 2D track calculations are performed by a
camera's onboard sensors. When disabled, the 2D track calculation is
performed by the PC (in Nexus). The default is off.
Marker Velocity Maximum velocity at which a marker will be tracked,
expressed as the percentage of image width per second. The default is 5.

Important
These properties affect the quality of the motion capture data. You
cannot adjust them after data capture, so it is important to optimize
these before you collect data intended for analysis. In subsequent
sessions, you may wish to configure additional properties to suit the
needs of your motion capture application.

For further details about each of the Vicon Camera properties, see Vicon Camera

properties in the VIcon Nexus Reference Guide.
6. When you have finished adjusting the Vicon Cameras settings, in the Settings
section, ensure that Grayscale Mode is set to Auto.
7. At the top of the System tab, click the Save button to save your system
configuration settings to a .system file in the Systems Configurations folder (see
Manage configurations in Vicon Nexus on page 21).

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Set up mixed Vicon camera systems
Vicon Nexus (version 2.4 and later) enables you to run mixed Vicon camera systems
consisting of Vicon Vero cameras (v1.3 and v2.2), Vicon Vantage cameras (V5, V8, V16)
and/or MX T-Series cameras (T10, T20, T40, T160, or S Edition) and Bonita Optical
cameras (B3, B10). You can also use Vicon Vue and Bonita Video cameras in the same
mixed system.

Caution
The use of mixed systems that include Vicon cameras older than T-Series and
Bonitas is not supported and full functionality cannot be guaranteed.

For systems involving only Vero, Vantage and Bonita cameras, the shutter period
characteristics for all cameras match exactly. Irrespective of individual cameras' strobe
(shutter) settings, the center alignment of these periods in any Vero/Vantage/Bonita
camera in the same system align exactly. You do not need to make any adjustments to
ensure that this alignment occurs.
However, for systems involving Vicon MX T-Series cameras, depending on your
requirements (see When are differences in strobe timings important? on page 60),
you may need to make some manual adjustment (see the following steps).

Important
Support for mixed systems' center strobe alignment requires Vicon firmware
700 or later. Vicon recommends that you always update to the latest
firmware.

Due to the differences in strobe timings between the current Vicon cameras (Vero,
Vantage and Bonita cameras) and the MX T-Series cameras, in situations where very
small timing differences are considered to be relevant and greater than other accepted
limitations (such as skin movement artifacts), ensure that the camera strobe periods
match by setting the Strobe Intensity for the MX T-Series camera(s) to maximum as
described below.

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To obtain consistent strobe timing and sensor exposure in mixed camera systems that
include T-series:
1. In the System Resources tree, select the MX T-Series camera(s).
2. In the selected camera's Properties pane, in the Settings section, ensure the
Strobe Intensity is set to its maximum.
This ensures that the center of the strobe pulse and shutter period for the Vero/Vue
/Bonita cameras matches that of the MX T-Series cameras.

When are differences in strobe timings important?
In situations where very small timing differences are considered to be relevant and
greater than other accepted limitations (such as skin movement artifacts), ensure that
all the camera strobe periods match by setting an appropriate value in the Strobe
Intensity for the cameras you are using. If all cameras are of the same type, this value is
the same for all cameras, but for systems that include both T-series and other current
Vicon cameras, set the TSeries' Strobe Intensity to its maximum, as described above.
Situations that may warrant this consideration include studies where very fast ballistic
movements are expected and/or where very small markers are likely to be in close
proximity.

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Configure video cameras for digital video capture
You manage the identification and configuration settings for each digital video camera
connected to your Vicon system with the Video Cameras node in the System Resources
pane. Using this node, you can also remove or reorder video cameras.

Note
References to "Vicon video camera" apply to the use of Vicon video cameras
(Vicon Bonita and Vicon Vue). The following instructions also apply to Basler
cameras that are supported by Vicon Nexus. For details of how to set up a
Vicon system that includes video cameras, see the PDF PC Setup for Vicon
systems.

The Video Cameras node is displayed under the Local Vicon System node when one or
more video cameras is connected to the Nexus host PC and Vicon Nexus is in Live
mode, or when a previously saved file containing video cameras is loaded. It lists each
video camera connected to your Vicon system. For each camera, the node name
includes the camera number, the camera type in parentheses and the frame rate in
brackets, for example, #DV2 Over Door (Bonita 720c) [50Hz].

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Important
For this node to be displayed, Nexus must be in Live mode (click the Go Live
button) or a previously saved trial must be loaded. Before managing video
cameras in your Vicon system, ensure that the desired system configuration
has been selected in the System Resources pane (see Manage configurations
in Vicon Nexus on page 21). This topic assumes that the digital video camera
is connected and feeding data through the FireWire or GigE port. For
information on setting up this port, see the documentation provided with your
FireWire card or GigE port.

You can connect a digital video camera to the Nexus host PC. You can connect
supported Basler video cameras to the FireWire or GigE port on the PC and then
capture reference video for use with your optical motion capture data. You can overlay
the Vicon optical motion data onto the digital video images from the video cameras in
the Camera view using the 3D Overlay option, from the View menu. If required, you can
burn this information into the digital video image and export the .avi file for viewing in
another application using the Configure the Export 3D Overlay Video operation.
To configure video cameras for digital video capture:
1. Ensure Nexus is in Live mode (in the Resources pane, click Go Live).
2. In the System Resources tree, select the node whose properties you wish to
configure:
Video Cameras node, for all digital video cameras
A sub-node, for a specific video camera
Note that if you are configuring a Vicon video camera, the node will not become
green until you specify the Destination IP Address.
Also note that cameras with gray icons are connected to the network but are not
contributing data. For example, if you have connected Vicon Bonita video
cameras, but your Vicon connectivity device does not support jumbo packets, the
icons for the Vicon video cameras will remain gray. For more information and
help with upgrading your system, contact Vicon Support.
3. In the Properties pane at the bottom of the System Resources pane, view or
change settings for the required properties.
When you first set up your Vicon system, you must configure at least the
following properties in the order shown. In subsequent sessions, you may want to
configure additional properties to suit the needs of your motion capture
application.

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Section

Property name

Hardware

Destination IP Address (Vicon video cameras)

Settings

Capture Path (enter a separate HDD or an SSD drive for each
camera)
Video Gain and Brightness Offset (Vicon video)
Camera Gain and Camera Brightness (Basler)

Frame

Requested Frame Rate

Rate:
Settings

Shutter Duration and Camera AOI (Basler),

Frame

Packet Size (Baslers using Firewire)

Rate
Hardware

Trigger Source (Basler)

Calibration

Focal Length (millimeters) (if you will be using Aim Cameras)

For further details about each of the Video Camera properties, see Video Camera

properties in the Vicon Nexus Reference Guide.
4. If you are using Basler cameras, to align the shutters with the rest of the Vicon
system, in the System Resources tree, right-click the Video Cameras node and
then click Align Shutters (Basler).
5. At the top of the System tab, click the Save button to save your system
configuration settings to a .system file in the Systems configurations folder (see
Manage configurations in Vicon Nexus on page 21).

Tip
When you plug a video camera into the Vicon system, the system
automatically assigns it a number. To reorder video cameras, select the
camera in the Reorder Devices dialog box and click Move Up or Move Down.
Then click OK.

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Aim Vicon cameras
Note
Aiming cameras is useful for providing an initial, approximate calibration,
before you fully calibrate the cameras as described in Calibrate Vicon cameras
on page 97.

Before you aim your Vicon cameras, ensure that they are displayed in the 3D
Perspective view.
Vicon camera positioning changes in real time. When you physically move a camera in
the capture volume, you should be able to see that its representation moves
correspondingly in the 3D Perspective view. If you can't see the cameras in the 3D
Perspective view, or if you want to change the way the cameras are displayed, press F7
to open the Options dialog box, and on the left, ensure Camera Positions is selected. If
required, change the Properties on the right.
When you have roughly positioned the cameras in the volume, you can use the Aim
Cameras section of the System Preparation Tools pane to optimize their positions,
before running a full camera calibration.

Important
To aim Vicon cameras, you must use the calibration device supplied with your
Vicon system. To aim digital video cameras, you must use an Active Wand.

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To optimize the position of Vicon cameras:
1. In the Resources pane, ensure Nexus is in Live mode.
2. In the Options dialog box (press F7), under the General View Options section,
select the Target Volume option.
3. On the right side of the dialog box, update the properties of the target volume to
reflect the dimensions of your capture volume.
4. View the Vicon camera feedback by doing the following:
a. In the view pane, select the Camera view.

b. In the Camera view toolbar, on the View drop-down list, select 3D Overlay.

c. In the System Resources tree, click the cameras that you want to aim to
select them.

A virtual representation of your target volume is overlaid on the 2D data
from the camera image.

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5. In the System Preparation Tools pane, expand the Set Volume Origin section and
from the L-Frame drop-down list select the Active Wand or 5 Marker Wand & LFrame calibration object.
6. In the capture volume, place the calibration object flat on the floor in the center
of the capture volume at the desired origin position.
In the Aim Cameras section, click Start to begin the camera-aiming process.
Nexus starts attempting to identify the calibration object in each camera view,
and the Start button switches to its Stop setting.
7. In the System Resources tree, select the camera you want to position and ensure
that you can see the calibration object in the Camera view.
8. Physically move a Vicon camera in the capture volume and check its coverage
against the target volume.
9. Repeat steps 7–8 for each Vicon camera, until they are all correctly aimed at the
calibration object.

Mask unwanted reflections
Masking enables grayscale blobs that are generated from reflections of objects other
than markers (eg, reflections from floor or furniture, or opposing camera strobe rings) to
be ignored by the Vicon cameras. In capture volumes where this spurious data is
present, camera masking improves calibration robustness and reconstruction quality.
In Nexus, masking is shown as a grid of small blue tiles superimposed over the camera
image in a Camera view, each cell of which can be set to obscure unwanted reflections
that are seen by a camera.
Vicon Nexus offers both automatic masking and tools for manual masking. If you have a
large number of reflections in your capture volume, it is a good idea to create camera
masks automatically first. You can then eliminate any remaining reflections by creating
masks manually.
For more information, see:
Automatically create Vicon camera masks on page 67
Manually create Vicon camera masks on page 68

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Automatically create Vicon camera masks
To automatically create camera masks:
1. Remove from the capture volume any unnecessary objects, such as calibration
objects. For best results, the capture volume should be entirely free from objects
likely to cause background interference.
2. In the Resources pane, ensure Nexus is in Live mode.
3. From the System Resources tree, select all Vicon cameras.
4. From the view pane toolbar, select Camera to display the 2D data being captured
by each selected camera in a separate Camera view.
5. From the View drop-down list at the top of the view pane, ensure that the 3D
Overlay and Combined options are cleared.

6. In the Options dialog box (F7), under the General View Options section ensure
that the Threshold Map option is selected.
7. Ensure you have adjusted camera settings as described in Configure Vicon
optical cameras for data capture on page 55. Any reflections are clearly visible
in the Camera view, typically as non-circular areas of grayscale or edge data.
Note that as reflections can severely affect the camera data rates, you may find
that the camera overloads. In this case, the camera automatically sends edge
data instead of full grayscale.
8. In the System Preparation Tools pane, in the Mask Cameras section, click Start.

9.
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9. The Start button switches to its Stop setting. Nexus starts recording the data
visible to each of the cameras connected. Any camera masks created are
displayed as blue cells in the Camera views for affected cameras. If there is no
data visible to a particular camera, Nexus does not create any masks for it. About
30 seconds of recording is generally sufficient to enable Nexus to collect the
data visible to the cameras.
10. After about 30 seconds, click Stop. If you still see unwanted reflections, you can
start and stop the Mask Cameras option again until you have hidden the
reflections, or mask any remaining reflections manually.

Manually create Vicon camera masks
You can manually create masks to eliminate any reflections in the capture volume that
are visible to the cameras. If you have a large number of reflections in your capture
volume, it is a good idea to create camera masks automatically first (see above).
To manually create camera masks:
1. From the capture volume, remove any unnecessary objects, such as calibration
objects. For best results, ensure the capture volume is entirely free from objects
likely to cause unwanted reflections.
2. From the System Resources tree, select all Vicon cameras.
3. From the view pane toolbar, select Camera to display the 2D data being captured
by each selected camera in a separate Camera view.
4. From the View drop-down list at the top of the view pane toolbar, ensure that
the 3D Overlay and Combined options are cleared.
5. In the Options dialog box (F7), under General View Options, ensure that
Threshold Map is selected.

Tip
The Threshold Map default color is blue, but you can change the color
in the Options dialog box. In the following descriptions, the masking
tiles are described as blue.

6.
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6. Ensure you have adjusted camera settings as described in Configure Vicon
optical cameras for data capture on page 55. If reflections are present, they
should be clearly visible in the Camera view, typically as non-circular areas of
grayscale or edge data. Note that as reflections can severely affect the camera
data rates, you may find that the camera overloads. In this case, the camera
automatically sends edge data instead of full grayscale.
7. From the view pane toolbar, use the following buttons to obscure any unwanted
reflections visible to the selected Vicon cameras. (When you click any of these
buttons, a grid of small blue tiles is superimposed over the camera image in each
Camera view.)
Paint a mask onto the camera
Click an individual tile, click and drag across multiple tiles, or hold down ALT
and click while dragging the mouse across an entire area of unwanted
reflections visible in the camera grid. You can drag the mouse horizontally,
vertically, or diagonally.
When a cell is painted, its background color changes from black to blue. The
camera mask consists of blue cells obscuring unwanted reflections.
Erase a mask from the camera
Click an individual tile, click and drag across multiple tiles, or hold down ALT
and click while dragging the mouse across an entire area of blue cells in the
camera grid. You can drag the mouse horizontally, vertically, or diagonally.
When an individual cell is erased, its background color changes from blue to
black, and any reflection that had previously been obscured is visible again.
Clear the mask from the camera
Click the button to automatically remove the entire mask from the camera.
When the mask is cleared, the background color of any previously painted cells
changes from blue to black, and any reflections that had previously been
obscured are visible again.

Tip
To zoom in on the images, right-click and drag the mouse forward (to
zoom in) or backward (to zoom out). To pan the image, click both mouse
buttons and drag

The camera masks are applied in real time and are saved along with your camera
calibration.

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Configure Vicon connectivity units
Vicon connectivity units are smart boxes that can be combined to create a distributed
architecture, enabling you to customize the number of Vicon cameras and supported
third-party devices in your Vicon system.
As part of setting up your Vicon system, you configure your Vicon connectivity unit(s)
for system communications and any GPO or remote triggering.
The Vicon Connectivity node is displayed under the Local Vicon System node when
Vicon Nexus is connected to the Vicon system and is in Live mode. It is displayed under
the Vicon Data node when Nexus is in Offline mode. It lists each connectivity unit
connected to your Vicon system.
Depending on the type of Vicon system you are running, your Vicon system
architecture will contain one or more of the following Vicon connectivity units:
Vicon Lock unit: Facilitates the integration of synchronous third-party equipment
with Vicon Vantage, Vicon Vero, and Vicon Bonita cameras, by providing or receiving
synchronization and/or timecode. Also provides connectivity for third-party analog
capture sources, such as force plates and EMG equipment. Connects to a PoE+
switch to which Vicon cameras and the host PC are connected.
If your Vicon system includes PoE or PoE+ switches, note that although they do not
appear as connectivity nodes in the System Resources tree, the cameras that are
connected to them are displayed.

Note
Except where noted, references to Vicon Lock, Lock units, and Lock apply to
all current models of the Vicon Lock unit (at the time of publication, this
includes Vicon Lock+, Vicon Lock Studio and Vicon Lock Lab).

MX Giganet: The primary connectivity unit in an MX T-Series system. To connect and
synchronize force plates and EMG devices, MX Giganets can be configured with a 64channel analog card. (This functionality is integral to Vicon Lock+ and Lock Lab
units.) You can incorporate units and components from an MX T-Series system into a
Vicon Vantage system. See the Vicon Vantage Reference Guide or contact Vicon
Support for details on configuring a combined architecture.

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If your Vicon system includes PoE or PoE+ switches, note that although they do not
appear as connectivity nodes in the System Resources tree, the cameras that are
connected to them are displayed.

Important
Before managing Vicon connectivity units, ensure that the desired system
configuration has been selected in the System Resources pane (see Manage
configurations in Vicon Nexus on page 21).

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Set up Vicon connectivity units
The Vicon Connectivity node lists each MX Giganet or Vicon Lock unit connected to
your Vicon system. For each unit, the node name includes the device position number,
any display name specified in the Identification property, and the device type listed in
parentheses, for example #1 Name (Lock+). For Lock Lab and Lock+, and for MX
Giganet if either or both analog option cards are installed, the sample rates are
displayed in brackets, and an Analog Card (Slot 1) sub node is displayed as appropriate.
If no analog source is selected, [No Source] is displayed after the device name.
The Lock or MX Giganet node enables you to manage the identification and
configuration settings for each connectivity unit included in your Vicon system
architecture. The node is displayed under the Vicon Connectivity node in the System
Resources pane when Vicon Nexus is connected to a Vicon system with at least one
Lock unit or MX Giganet unit and is in Live mode (click the Go Live button).
To configure connectivity units for analog data acquisition:
1. In the System Resources pane, click the Go Live button.
2. In the System Resources tree, select the node whose properties you want to
configure:
Vicon Connectivity node for all Vicon connectivity units
A sub node for a specific connectivity unit – the sub nodes in the System
Resources tree correspond to the IDs assigned by Nexus. If a connectivity unit
has automatically been designated as the synchronization master for the Vicon
system, its node name is displayed in bold.
The colored icon beside a connectivity node identifies the status of the device:
Green play button: Component OK (active). If an analog device is
connected, this status does not reflect the analog device's status.
Yellow pause button: Component is not fully set up or device has been
disabled in Status section of Properties.
Gray play button: Component connected but not contributing any data.
Red stop button: Component down (unavailable or disconnected).
In the Properties section at the bottom of the System Resources pane, view or
change settings for the desired properties.

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When you first set up your Vicon system, you must configure at least:
Name A name you supply, to enable you to identify this unit easily
Sync Out (if you are using synchronization functionality) The general purpose
output driver (*.gpo file) you specify here determines the output frequency of
the synchronization pulse. You can select a driver for each of the sync outputs.
For further details, see Go Further with Vicon MX T-Series or Vicon Vantage

Reference Guide.)
In subsequent sessions, you may wish to configure additional properties to suit
the needs of your motion capture application. For details about all the properties
for Vicon connectivity units, see Vicon Lock and MX Giganet properties in the

Vicon Nexus Reference Guide.
3. In the System Resources pane, click the Save button to save your system
configuration settings to a .system file in the Systems configurations folder (see
Manage configurations in Vicon Nexus on page 21).

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Configure supported devices
As part of setting up your Vicon system, you configure supported devices using the
Devices node in the System Resources pane.
The Devices node is displayed under the Local Vicon System node when Vicon Nexus is
connected to a Vicon system with at least one Vicon or supported third-party analog or
EMG device and is in Live mode. It is displayed under the Vicon Data node when Nexus
is in Offline mode. The Devices node lists each supported device connected to your
Vicon system.
For each device, the node name includes any display name specified in the Name
property, its approximate sample rate in brackets, and the device type in parenthesis,
for example, Name [2000Hz] (Analog EMG). The default name property displayed is
Name [1000Hz] (Analog EMG).
For analog devices, if no analog source is selected, [No Source] is displayed after the
device type. Channel sub nodes are displayed for any analog channels. Predefined
configurations for some devices are supplied with Vicon Nexus.

Tip
To add new device entries to this node, Vicon Nexus must be in Live mode
(click the Go Live button). Before managing other devices, ensure that the
desired system configuration has been selected in the System Resources pane
(see Manage configurations in Vicon Nexus on page 21).

To view a graph of one or more device output or component signals:
1. In the System Resources tree, expand the Devices node to show the devices
connected to your Nexus system
2. Select one or more devices, outputs or components.
3. From the view pane toolbar, select Graph.
4. If necessary, in the Graph view toolbar, from the Graph Type drop-down list,
select Components.
5. The Graph view displays a graph of the selected components.
For more information on configuring supported devices, see:
Configure force plates on page 75
Configure EMG devices on page 87

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Configure IMUs on page 89

Configure force plates
As part of setting up your Vicon system, you manage the connection and configuration
settings for supported force plates in your Vicon system with the appropriate force
plate node. You can select the required force plate node under the Devices node in the
System Resources pane when Vicon Nexus is connected to a Vicon system with at
least one force plate unit and is in Live mode. When Nexus is in Offline mode, the force
plate node is displayed under the Devices node of the Vicon Data node.
The Devices node lists each force plate connected to your Vicon system. For each
device, the node name includes any display name specified in the Name property, its
sample rate in brackets, and the force plate type in parentheses, for example, Name
[1000Hz] (AMTI AccuGait Force Plate). If no analog source is selected, [No Source] is
displayed after the device type. Channel - # sub nodes are displayed for each channel.
Predefined configurations for some supported force plates are supplied with Vicon
Nexus.

Important
To add new force plate entries to the Devices node, Nexus must be in Live
mode (click the Go Live button). Before managing force plates, ensure that the
desired system configuration has been selected in the System Resources pane
(see Manage configurations in Vicon Nexus on page 21).

Force plates data can be acquired through the analog capture functionality of a Vicon
connectivity device (Vicon Lock+ or MX Giganet ). This topic describes the analog
connection only. If your force plate has a digital output, it is possible that this data
stream can also be captured, but this depends on the data stream's format and the
equipment's manufacturer. For information on the digital data streams that can be
used with Vicon systems, contact Vicon Support.

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To configure force plates for analog data capture:
1. In the System Resources pane, click the Go Live button.
The first time you use Nexus, the Devices node is empty. You must add and
configure a new force plate device before it will be displayed in the System
Resources tree.
2. In the System Resources tree, right-click the Devices node, point to Add Analog
Device and from the context menu select the type of force plate that is
integrated in your Vicon system.
The selected force plate node automatically expands to display the newly
created device. (For Motekforce Link treadmills, two new device nodes are
displayed, one for each plate.) If the appropriate type is not displayed, contact
Vicon Support.
The colored icon beside a force plate node identifies the status of the device and
of any connected analog source:
Green play button: Component OK (active or connected); if an analog
device is connected, the analog source is selected and all channels are
configured.
Yellow pause button: Component is not fully set up (e.g., not all channels
have been assigned a pin or the calibration matrix has not been configured).
Gray play button: Component connected but not contributing any data.
Red stop button: Component down (unavailable or disconnected).
These colored icons correspond to those used for the device summary in the
Status Communications pane.
3. In the Properties section at the bottom of the System Resources pane, view or
change settings for the following properties:
a. In the General section, enter a Name.
b. In the General section, go to the Calibration File field, and load the
manufacturer's calibration file:
If the calibration file is not listed in the drop-down list, click the ellipsis
(...) next to the Calibration File field to browse to the relevant location,
and select it. The file becomes available in the drop-down list.
Select the calibration file. (For Motekforce Link treadmills, note that a
single calibration file is used for both plates.)
If not supplied by the manufacturer's calibration file, you can set the
device Dimensions, Position, Orientation, and Origin in those Properties
sections.

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c. If there is no calibration file, click Show Advanced at the top right of the
Properties section and enter the Calibration Matrix 6x6 Matrix values
manually.

Important
The Matrix values must be entered, either via a calibration file or
by manual entry, in order for the force plate to become active.

d. In the Source section, select a Source (the Vicon connectivity device to
which the device is attached) from the drop-down list.
The Source drop-down list contains all connected Vicon connectivity
devices; a USB force plate will have its Source drop-down list populated
with connected USB devices of the required type.
e. In the Source section, use the Fill button to populate the input
connections sequentially (if these are consecutive on the Vicon
connectivity device).
f. In the Source section, select the Gain for the Source from the choice of
gains available for the Vicon connectivity device.
4. In the System Resources tree, if necessary, expand the force plate node to
expose the Force, Moment and CoP (Center of Pressure) channels.
The colored icon beside the output node identifies the analog channel status:
Green arrow: Analog channel connected to source device.
Yellow arrow: Analog channel has not been assigned a pin.
5. To tare the force plate at zero load, in the General section, click the Zero Level
browse button and enter the matrix properties.

Tip
You can also tare the force plate by right-clicking on the force plate
name in the System Resources tree and selecting Zero Level.

6. In a 3D Perspective view, ensure that a gray or colored rectangle with the
number 1 on it, representing the force plate, is displayed in the capture volume
where you have positioned it.
If you have multiple force plates configured, they will be numbered in the order
they appear in the System Resources tree.

7.
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7. In the capture volume, have someone step onto the force plate. You should see
the force vector being displayed in real time.
8. At the top of the System Resources pane, click the Save button to save your
system configuration settings to a .system file in the Systems configurations
folder (see Manage configurations in Vicon Nexus on page 21).
9. From the System Resources tree, expand the force plate node and select the
Force output.
10. Switch to a Graph view.
11. If necessary, select Components from the Graph Type drop-down list. A real-time
graph of the Force output is displayed.
12. Verify that the vertical (Fz) force component is equal to [known mass * 9.81].
For more information, see:
Force plate minimum setup requirements on page 79
Change force plate display options on page 80
Visualize and record Force Threshold on page 83
View combined output from multiple force plates on page 84
Usage recommendations for Motekforce Link treadmill on page 86
See also Force plate properties in the Vicon Nexus Reference Guide.

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Force plate minimum setup requirements
For a force plate to appear in a 3D Perspective view, you must configure at least the
following properties:
Source
Calibration Matrix
Position (X, Y, Z)
Name: Assigning a force plate name is recommended, especially if you are setting up
more than one force plate.
For a force plate to appear in Live mode in the 3D Perspective view, you must fully
configure:
Source
Calibration Matrix
Dimensions (X, Y)
Origin
The Position and Orientation are necessary for the CoP (Center of Pressure) and Force
vector to be represented correctly, but they can be changed according to the setup. In
subsequent sessions, you may wish to configure additional properties to suit the needs
of your motion capture application.

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Change force plate display options
You can configure colors and other force plate display options in the Options dialog
box (F7).

You turn a display option on or off by selecting or clearing the corresponding check
box.

Tip
You can set colors for some of the display options. If a default color is listed as
Context Color (this indicates the color is set to the system default) and you
want to change it, click the down arrow to the right of the drop-down list, and
clear the Macro check box. You can then activate the color picker.

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To view force plates in a 3D Perspective view, ensure the Force Plates check box on
the left side of the Options dialog box is selected. You can change the following
options:

Force Plate section
Property

Description

Draw

When selected, the force plate appears in the View pane.

Plate
Draw

By default, each force plate displays a number (e.g., 1, 2, 3). The number

Number

corresponds to the order in which the force plates appear in the System
Resources tree. You can turn off the number display by clearing the
check box.

Draw

You can configure how the force plate axes appear in the 3D Perspective

Axes

view by selecting the Draw Axes check box. The axes appear below the
floor plane of the volume.

Axis

Width of the axis. Set the axis width by typing a value or by moving the

Width

slider.

Axis

Length of the axis. Set the axis length by typing a value or by moving the

Length

slider.

Foot Contact Colors section
If you have designated a force plate to be a left or right foot contact, by default Nexus
displays a left-foot contact force plate in red in the 3D Perspective view, a right-foot
contact force plate in green. An auto-detect force plate is displayed in light gray, and
an invalid force plate (neither left, right nor auto-detect) is displayed in dark gray.
To change the default colors for the force plate display, in the Options dialog box,
select the Force Plates option, and in the Properties pane on the right, click on a color
in the Foot Contact Colors section to activate the color picker.

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Force Vector section
You can visualize the force vector by selecting the Draw and Draw Butterfly check
boxes. Then you can set the quality of the vector display, as well as the radius and
scaling factor (length), the butterfly style (whether the butterfly is represented as
transparent, as a wireframe or both), and color.
Setting a Scaling Factor value causes the vector to be displayed as an arrow originating
from the force plate in the direction of the force.
Values below the Force Threshold (N) are not visualized as force vectors on the plate.
This setting does not affect the value for Force Threshold that is written into a
recorded trial (see Visualize and record Force Threshold on page 83).

Moment Vector section
You can select whether the moment vector is visually represented in the 3D Perspective
view, as well as the quality, radius and color of the moment vector display.
You can see the results of your settings in the 3D Perspective view as you configure an
option.

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Visualize and record Force Threshold
The Force Threshold of a force plate specifies the noise floor value in Newtons. Forces
below this value are assumed to be noise and are clamped to zero.
An Options setting for force plates enables you to specify a different value for the
Force Threshold depending on whether you are recording data or displaying a trial.
The value for the Force Threshold that is set in the System Resources pane for the
force plate affects the values that are written into a recorded trial. For example, if the
Force Threshold is set to 25 N, all values below this are considered noise and values
of zero are recorded.
The value for the Force Threshold that is set in the Options dialog box ensures that
values below this threshold are not visualized as force vectors on the plate. This
prevents very small values, which are simply noise, from creating a distracting
‘flickering’ force vector on the plate. If you are distracted by flickering while viewing a
trial, raise this value to remove the flickering. This does not affect the value for Force
Threshold that is written into a recorded trial.
To specify the Force Threshold that is recorded for a force plate:
1. Ensure the system is in Live mode.
2. In the System Resources tree, select the force plate.
3. In the Properties pane, ensure the Advanced properties are displayed.
4. In the General section, change Force Threshold (N) from the default (25 N) to the
required value.
Values below this magnitude are ignored and are recorded as zero.
To specify a value for visualizing the force vector:
1. Press F7 to open the Options dialog box.
2. On the left click ForcePlates.
3. In the Properties pane on the right, in the Force Vector section, change the
Force Threshold (N) to the required value (the default is 25 N).
Regardless of the setting of the Force Threshold in the System Resources pane,
the force vector that is displayed in the view pane is below the threshold that is
set in the Options dialog box. For example, if you set the value to 10 in the
System Resources pane, but left it at 25 in in the Options dialog box, a value of
15 would be prevented from causing flickering, but would be recorded in saved
trials.

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View combined output from multiple force plates
You can combine selected outputs from multiple force plates, both in Live mode and
when reviewing captured trials in Offline mode. For example, in trials where the
subject's feet land on separate force plates, you can examine the combined landing
force or overall CoP from both feet.
To view combined output from multiple force plates:
1. In the Options dialog box (press F7), on the left, click ForcePlates and in the
Properties pane on the right, in the Force Vector section, ensure Draw Combined
Force Vector is selected.
2. In the System Resources tree, CTRL+click to select the required outputs from
each force plate.
Ensure you select identical outputs from each force plate.

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3. In a Graph view, in the Graph type list, select Combined Forceplates.

4. In the Graph view, the combined output you selected is displayed.

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Usage recommendations for Motekforce Link treadmill
Note the following recommendations for setting up and using a Motekforce Link
treadmill with Nexus:
For ease of use, align the Vicon world Y-axis with the direction of walking on the
treadmill. To achieve this, you can either move the treadmill in the laboratory to align
with the Vicon world axes in Nexus, or change the Vicon world axes to align with the
position of the treadmill. You can then set the incline of both plates of the treadmill
by adjusting the XOrientation property of the force plate.

Assuming you follow this advice so that the direction of walking on the force plates
aligns with the Vicon Y-axis, and the left-right (medial-lateral) direction aligns with
the Vicon X-axis, inclination of the force plate will correspond to a rotation of the
plate about its X-axis. For example, to set a 10 degree inclination of the treadmill, you
would set a 10 degree X (deg) rotation in the plate's Orientation properties.
Each capture must use only one inclination of the treadmill. If you need to capture
multiple inclinations, to enable you to switch easily between different inclinations,
create a number of separate system files: one for each required inclination.

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Configure EMG devices
EMG data can be acquired through the analog capture functionality of a Vicon
connectivity device. If your EMG device has a digital output, it is possible that this data
stream can also be captured, but this depends on the data stream's format and the
equipment's manufacturer. For more information on the digital data streams that can
be used with your Vicon system, contact Vicon Support.
To configure EMG devices for data capture:
1. If Vicon Nexus is not in Live mode, in the System Resources pane, click the Go
Live button.
The first time you use Nexus, the Devices node is empty. You must add and
configure a new EMG device before it will be displayed in the System Resources
pane.
2. In the System Resources tree, right-click Devices, point to Add Analog Device or
Add Digital Device and from the context menu select the type of EMG device
that is integrated in your Vicon system.
The Devices node automatically expands to display the newly created EMG
device with its attendant output:
An analog Accelerometer will have an Acceleration output
An analog EMG will have a Voltage output
A ZeroWire EMG will have a Voltage and a Foot Switch output
3. In the System Resources tree, select the node whose properties you wish to edit:
Generic Analog Device sub node for all devices
A sub node for a specific device
The colored icon beside a device node identifies the status of the device and of
any connected source:
Green play button: Component OK (active or connected); if an analog
device is connected, the source is selected and all channels are configured.
Yellow pause button: Component is not fully set up (e.g., not all channels
have been assigned a pin or the calibration matrix has not been configured).
Gray play button: Component connected but not contributing any data.
Red stop button: Component down (unavailable or disconnected).
4. In the Properties section at the bottom of the System Resources pane, view or
change settings for the following properties:
a.
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4.

a. In the General section:
Enter a Name to enable you to identify the device.
Set the Delay Compensation (in frames). All devices have a delay
compensation value which adjusts the synchronization offset between
the device and the Vicon data. The Delay Compensation slider bar
enables you to correct this difference. Values can be set between -10
and 10 (the default is 0). Note that analog data collected with a Vicon
Lock+ or an MX Giganet should already be synchronized, so in this case,
this value should be set at 0.
Set the Amplifier Gain. The voltage gain scale factor. Can be set
between 1-1000. The default setting depends on the device.
b. In the Source section, select a Source (the Vicon connectivity device to
which the accelerometer or EMG is attached) from the drop-down list.
When you first set up your Vicon system, you must configure at least the Name
and Source properties, add channels and designate the Source for each channel.
In subsequent sessions, you may wish to configure additional properties to suit
the needs of your motion capture application.
5. In the System Resources tree, expand the device node you added and select a
device output sub node which corresponds to an output from the device (such
as Acceleration for an accelerometer, or Voltage for an EMG device).
6. Right-click the device output and add an output component or components:
For an accelerometer or analog EMG, choices are:
Add Component (or 2, 4, or 8 Components)
For a ZeroWire EMG, choices are:
Under Voltage:
Add EMG (numbered 1 - 16)
Remove Channels (if you have added channels)
Enable Auto Populate (or Disable Auto Populate if the AutoPopulate Properties
box is selected)
Under Foot Switch:
Add FSW (designated A1-A4 and B1-B4)
A new component node (or nodes) is added to the tree.
The colored icon beside the device output node identifies the analog channel
status:
Green arrow: Analog channel connected to source device.

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Yellow arrow: Analog channel not fully set up (e.g., not all channels have been
assigned a pin or the calibration matrix has not be configured).
7. In the Properties pane under the General section, specify a Name for the node or
nodes you have added.
For the ZeroWire EMG, Name is the only property setting necessary.
8. In the Properties Source section:
a. Assign the Pin to one of the available pins on Source device. After you
have assigned a pin, the status icons will turn green.
b. Specify the Gain (V).
c. Set the Zero Level.
9. At the top of the System Resources pane, click the Save button to save your
system configuration settings to a .system file in the Systems Configurations
folder (see Manage configurations in Vicon Nexus on page 21).
For more information on the properties for EMG and other devices, see System

Resources nodes in the Vicon Nexus Reference Guide.

Configure IMUs
To enable you to capture data from Vicon IMUs (Inertial Measurement Units) and
optical markers simultaneously, you can use IMUs as digital devices in Nexus to stream
and capture data. You can use IMUs to preview data in real time and to capture data
onto the IMU's internal memory. You can then plug the IMUs into your PC via USB and
use Nexus to download the captured data.

Important
Vicon IMUs are supported for use with Nexus for research purposes only. For
full sensor safety and regulatory details, see the IMeasureU Sensor Safety and
Regulatory Information, available from the Vicon website.

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Before you begin using IMUs with Nexus, note the following points:
Windows 10 and above only is supported. Ensure the latest Windows 10 updates are
installed.
To use Vicon IMUs in Nexus, first plug the supplied Bluetooth® (BLE) dongle into the
relevant Windows PC. Ensure that its drivers have been updated: you can do this
using the Windows Device Manager.
To enable further setup and control of your IMUs after they are paired and
recognized by Windows 10, you can download IMU Lightning desktop software. IMU
Lightning enables you to see the status of IMUs outside of Nexus and is useful in
certain troubleshooting situations.
IMUs have five collection modes: 100 Hz (9-axis), 250 Hz (6-axis), 500 Hz (6-axis),
500 Hz (9-axis), or 1000 Hz (3-axis). To accommodate the IMUs, ensure that your
Vicon system is running at a compatible frame rate.
Nexus supports the use of up to four current Vicon IMUs.
You can transfer the data that is collected and stored on your IMUs onto your PC
using the IMU Transfer pane in Nexus (see Transfer data from IMUs on page 227).
To enable transfers to work, ensure you have downloaded and installed the CP210x
USB to UART Bridge VCP Drivers.

Set up IMUs for capture
The following are brief notes on working with IMUs with Nexus. For more information
on setting up and using IMUs to stream and capture data, see the IMeasureU
documentation.
For more detail on working with IMUs and Nexus, watch the Vicon videos, IMU
Unboxing, Introduction to using Vicon IMU with Nexus, and Nexus and the IMU
Research app, available on YouTube.

1.
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1. If necessary (see previous points on page 90), download and install IMU
Lightning.
2. Ensure that the Bluetooth® dongle is plugged into the PC and that its drivers are
up-to-date.
3. Turn on the IMUs and pair them to the relevant Windows computer, via
Bluetooth settings in Windows 10.
4. In Nexus, add the IMUs as digital devices and in the Properties pane, specify the
required settings:
a. In the System Resources pane, expand the Local Vicon System node, then
right-click the Devices node, point to Add Digital Device and click Add
IMeasureU Sensor.
b. In the Properties pane below, specify a Name and Sensor Number:
Property

Description

Name

The identifier that you want to give to the IMU.

Sensor

The unique serial number of the device, which is found on

Number

the tag on the side of the IMU. Although you enter only the
digits on the tag, this is an eight-digit number that is
padded with four zeros when displayed in the Log.

For more information on the available properties, see IMeasureU Sensor
node in the Vicon Nexus Reference Guide.
c. Note that if the connection to the IMU is lost (the device is displayed as
gray in the System Resources pane), you can click the Sensor Reconnect
button to reconnect. This button is not available while you are capturing a
trial.
When you have specified a name and number, in the Resources list, the Play icon
next to the IMU name turns green.

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5. If necessary, change the collection mode (frequency) at which the IMUs are to
run.
To do this:
a. In the Resources list, ensure the IMUs are selected.
b. To display the axes for the IMUs, in the view pane, select Graph view.
c. In the Properties pane, from the Mode list, select the required frequency.

d. In the Graph view, the graphs change to reflect the selection.

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Note
If you need to calibrate the IMUs (normally only necessary when you
update the camera firmware or if an offset occurs), see Calibrate IMUs
on page 231. Note that, for calibration, you must set the collection
mode to 100 Hz.

6. Attach the IMUs to the subject.
7. Set up and start capture in the usual way (see Capture the required movement
on page 137 in the Vicon Nexus User Guide ).
For more information, see Work with IMUs on page 222.

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Prepare a data storage location
Before you capture and process a trial, you must create a hierarchical structure for
storing and managing all the data associated with the motion capture trial. You do this
in the Communications pane, on the Data Management tab.
For a video guide to database management, see the Vicon video, proEclipse: Preparing
and managing your database, which is available on YouTube.
To prepare a location for your trial data:
1. In the Communications pane, click the Data Management tab.
2. On the toolbar, click the Show main proEclipse menu button.

3. Click Manage Eclipse Databases, and in the Manage Eclipse Databases dialog
box, click the Add New button to enable you to locate and register a database
folder. (Registering a folder enables you to select it in the Currently Registered
Eclipse Databases list and from the recently used files that are displayed when
you click the Show main proEclipse menu button.)

Note
A database is just a folder structure where your Nexus files will be
saved. Generally, you can create a database in any unrestricted location.

4. Select a location on your local hard disk for the database folder, or if required,
click Make New Folder and enter a name for your folder. Click OK.
5. In the Manage Eclipse Databases dialog box, the folder that you just selected or
created appears in the Currently Registered Eclipse Databases list. Click Close.

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All registered databases are also available when you click the Show main
proEclipse menu button.

6. On the Data Management tab, click on name of the folder you just created,
ensuring its name appears in the live link at the top left of the tab.

Tip
To check that your hierarchy of folders appears as expected, click the
live link to open an instance of Windows Explorer, where you can see
the folder you created.

7. Ensure the folder name is still selected in the hierarchy displayed on the left of
the Data Management tab, and create a hierarchy of data folders in which to
store your data. A good practice is to make sure all your data goes into a session
folder. To do this:
a. Add a top-level folder by clicking the green New Patient Classification
button

. You can change its name as required. Generally, this classifies

a group of subjects such as Men/Women, Old/Young, or Target Population
/Controls.
b. In the left hand panel, click the new patient classification that you just
added and then add a patient folder by clicking the yellow New Patient
button

. Again, you can rename it as required.

c. In the left-hand panel, click the patient folder that you just added and then
add a session folder by clicking the gray New Session button

. Rename

it as required.
8. Select the new session folder by clicking it on the Data Management tab.
You now have an active session, ready to store your preliminary capture.
For more detailed information on data management, see Data management with Nexus
in the Vicon Nexus Reference Guide.

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Calibrate a Vicon system
The following topics cover calibrating the Vicon system, including the Vicon cameras
and any video cameras, for motion capture.
After you have configured your system (see Prepare a Vicon system on page 43), the
next setup step is to calibrate the Vicon cameras and define the origin of the capture
volume. Calibration enables Nexus to determine the positions, orientations, and lens
properties of all the Vicon cameras and to produce accurate 3D data.

Important
Vicon recommends that you calibrate your Vicon cameras after any changes
to your system and each day, before you capture any data. This ensures that
any accidental changes in your setup (such as a camera being knocked while
the system was unsupervised) does not influence the quality of your data. You
can perform the level of camera calibration that suits your requirements: a full
camera calibration or a calibration refinement.

For more information see:
Calibrate Vicon cameras on page 97
Set the volume origin on page 101
Calibrate the floor plane on page 103
Manage camera calibrations on page 105
A Vicon Nexus 2 Calibration video showing these procedures is available on YouTube.

Note
As the videos were recorded using an earlier version of Nexus 2, you may
notice small differences in the user interface.

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Calibrate Vicon cameras
To calibrate Vicon cameras, you use the relevant sections of the System Preparation
Tools pane.

To perform a camera calibration, you need a Vicon calibration device, which is supplied
with your Vicon system. Note that, to use the following process to calibrate supported
digital video cameras, as well as optical cameras, you must use an Active Wand, which
must be set to Strobe mode. (If you are not using an Active Wand, you can calibrate any
supported video cameras using the legacy Static Video Calibration section of the
System Preparation Tools pane. For more information, contact Vicon Support.)
Camera calibration describes the capture volume to the system, enabling Nexus to
produce accurate 3D data. During camera calibration, Vicon Nexus creates a calibration
parameters (.xcp) file. This file contains the calibration settings and threshold data
specified for the Vicon cameras (as well as any supported video cameras) in your Nexus
system and is used when data from these cameras is processed.

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Important
Vicon recommends that you calibrate your Vicon cameras each day before you
capture any data. This ensures that any unexpected changes in your setup
that may have occurred when the system was unsupervised (such as someone
accidentally knocking a camera slightly out of position) will not influence the
quality of your data. You can perform the level of camera calibration that suits
your requirements: a full camera calibration or a calibration refinement.

To calibrate Vicon cameras in Nexus:
1. Ensure you have aimed and masked the cameras (see Aim Vicon cameras on
page 64 and Mask unwanted reflections on page 66).
2. Remove from the capture volume all markers and the sources of any unwanted
reflections that have not been accounted for by camera masks previously
created in a Camera view.
3. In the Resources pane, ensure Nexus is in Live mode.
4. Display a Camera view.
5. In the System Resources tree, expand the Vicon Cameras node and select all
Vicon cameras.
6. In the System Preparation Tools pane

, expand Calibrate Cameras and from

the Wand list, select the calibration device that you are using.
7. If your Vicon system includes video cameras, in the Video Calibration Setup
section, click Activate to start video calibration mode. If your system does not
include video cameras, go straight to the next step.
If you have not already saved the current configuration, you will be prompted to
save it. Ensure its name is recognizable as a calibration and then choose whether
it will be Shared or Private (see Manage configurations in Vicon Nexus on page
21).

Tip
The settings for some video camera properties may differ in video
calibration setup mode from those in live capture mode. For these
properties, any changes made after you click Activate only apply during
video calibration setup mode. The properties revert to their live capture
settings after you click Deactivate.

8.
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8. In the Calibrate Cameras section, view or change settings for the required
parameters:
a. Select the appropriate Calibration Type: Full Calibration or Calibration
Refinement.

Tip
If you have not already calibrated all cameras, you cannot perform
a calibration with the Calibration Refinement option. For more
information on calibration refinement, see Understand camera
calibration refinement in the Vicon Nexus Reference Guide.

b. To automatically stop calibration when sufficient information has been
acquired, ensure Auto Stop is selected.
9. In the Calibrate Cameras section, click Start. The camera calibration process
starts, and the Start button switches to its Stop setting.
10. In the capture volume, wave the calibration wand throughout the area where you
intend to capture 3D data, ensuring that the markers on the calibration object
are visible to the cameras. Vicon Nexus begins to capture wand wave data.
11. Monitor the calibration progress and status:
In each Camera view, ensuring that the colored lines that identify wand frames
indicate that sufficient wand frames are spread across the intended 3D
capture volume. Also check the colored triangle in the lower right of each view
pane. The triangles change from red to green as the collection of calibration
information progresses, and then vanish when the cameras are calibrated.

Tip
If no cameras are visible in the Camera view, ensure that the Show
Uncalibrated Cameras option is selected in the Camera Positions
section of the Options dialog box (press F7). Also, if you are not using
the Vicon Control app, you may find it helpful to display the Nexus
window on a large screen where the person in the capture volume
can see the feedback in the Camera view while they are waving the
calibration wand, so they can see the area that they have covered.

In the System Preparation Tools pane, under the Camera Calibration Feedback
section check Wand Count values returned for each camera.

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On the strobe unit on the front of each camera, the status light flashes while
the camera registers valid frames where the whole wand is visible. When the
status light turns a solid green, the camera has collected enough data to be
calibrated successfully, usually 1,000 frames of valid wand data.
12. If Auto Stop was not selected, in the Calibrate Cameras section, click Stop.
Nexus starts processing the calibration information.
If you selected the Auto Stop option, Nexus automatically stops collecting
calibration information and starts processing it when sufficient calibration
information has been acquired.
Note that, for a system that includes video cameras, calibration is done in two
passes, so the Camera Calibration Feedback bar progresses from 0% to 100%
twice.
13. In the Camera Calibration Feedback section, monitor the progress bar until the
camera calibration process is complete and review the Wand Count and Image
Error data. As a general guideline, Nexus typically takes 15–60 seconds to
complete its calculations for a typical Vicon system setup, but this can take
longer for a very large system or low-specification PC. When the camera
calibration has successfully completed, it is automatically saved to an . xcp file.
For more information on the controls in this section, see Camera Calibration
Feedback section in the Vicon Nexus Reference Guide.

Tip
Because calibration feedback values are based on factors such as the
size of the capture volume and the camera lens type, it is not possible to
provide general guidelines on typical or acceptable ranges. Therefore, to
determine the optimal values for your Vicon system, shortly after the
system is installed, establish a baseline against which you can compare
future daily calibration values.

14. If you have calibrated video cameras, to exit video calibration mode and return to
your settings for live captures, click Deactivate in the Video Calibration Setup
section.
When you have finished calibrating the Vicon cameras, you are ready to Set the volume
origin on page 101.

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Set the volume origin
Setting the volume origin (global coordinate system) tells the Vicon system where the
center of your capture volume is and what its orientation is (x, y, and z axes), so that
subjects are displayed the right way up in the Nexus view pane and so that you can
change the way data is visualized. You normally set the volume origin immediately after
the previous step Calibrate Vicon cameras on page 97.
To set the volume origin, you need a calibration device, normally an Active Wand, which
is supplied with your Vicon system.
To set the global coordinate system:
1. Remove from the capture volume all markers and the sources of any unwanted
reflections that have not been accounted for by camera masks previously
created in a Camera view (see Mask unwanted reflections on page 66).
2. In the Resources pane, ensure Nexus is in Live mode.
3. Display a 3D Perspective view.
4. In the System Preparation tools pane, expand the Set Volume Origin section and
from the L-Frame drop-down list, select the type of calibration device you are
using to set the volume origin. (This will normally be the calibration device that
was supplied with your Vicon system.)

If it is impractical to place the wand in the required position, you can instead use
the One Marker or Three Markers options to set the origin. (The Three Markers
option creates two vectors that determine the orientation of the volume.) To use
these options, position the marker(s) in the volume and then click Set next to the
chosen option. You can then select the required marker(s) in the 3D Perspective
view. If you selected Three Markers, you are prompted to select an origin marker,
a primary (X-axis) marker, and secondary (Z-axis) marker.

5.
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5. In the capture volume, place the calibration object flat on the floor in the
position and orientation that you would like to be the origin of the global
coordinates system (often a force plate corner or another clearly marked area of
the volume).
6. In the Set Volume Origin section, click Start.
The calibration object tracking process starts, Nexus identifies the calibration
object in the capture volume, displays a 3D representation of it in the 3D
Perspective view, and switches the Start button to its Set Origin setting.
7. Click Set Origin to complete the calibration object tracking process. Nexus sets
the global origin and axes to correspond to the position and orientation of the
calibration object in the capture volume. In the 3D Perspective view, the floor
grid is displayed aligned with the capture volume floor and the representations
of the cameras are distributed in the position and orientation in which the
physical cameras are located around the capture volume. When the global
coordinate system has been successfully set, it is automatically saved to an .xcp
file. The latest calibration (.xcp) file is saved to the default location. This
calibration file is automatically copied to every subsequent trial captured.
8. Verify that the global coordinate system was successfully set by checking that
the system tracks the calibration object.
If it does not, check that you selected the correct calibration object from the LFrame drop-down list at the top of the tools pane. If not, repeat this procedure
from step 4, ensuring that you select the correct entry for the calibration device
you are using. After you have set the global coordinate system, you can display
the volume axes marker in the bottom corner of the 3D Perspective view.

9. Turn the display of the volume axes on or off in the Options dialog box (F7) by
selecting or deselecting Volume Axes under General View Options.

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Calibrate the floor plane
To ensure that your coordinate system is accurately aligned with the floor of the
capture volume, which is particularly useful if the floor is uneven, you can adjust the
position of the floor plane using markers in the volume to automatically define it.
To calibrate the floor plane:
1. Complete the camera calibration procedure (see Calibrate Vicon cameras on
page 97) and set the origin (see Set the volume origin on page 101).
2. Turn off the calibration object or remove it from the volume.
3. Scatter a quantity of the same size Vicon markers across the floor of your
capture volume. If you want Vicon Nexus to automatically recognize these
markers as floor plane markers, ensure that they outnumber any other groups of
markers (e.g, markers on a wand or markers that were used to focus cameras,
etc).
4. In the System Preparation Tools pane, expand the Set Volume Origin section,
click Show Advanced, and ensure that the options relating to Set Floor Plane are
as required:
Auto detect: Markers are automatically detected, based on the marker group
that defines the plane with the most markers. (If, when you click Auto detect,
the wrong markers are selected in the 3D Perspective view, you can add or
remove markers in the volume until selection is as required.) To ensure that the
tolerance setting (in mm), which specifies the height of the group of markers
that define the floor plane, is as required, click the drop-down arrow next to
Auto Detect, and set the tolerance to a value that prevents a large variance in
height (2mm is often enough).
Start: Enables you to manually select the markers that will determine the floor
plane by clicking the required markers in the 3D Perspective view.
Offset: Select the check box and set the amount (in mm) by which to adjust
the floor plane (default is zero) in X Y and Z planes. Because Nexus finds the
centers of the markers, set a Z-offset that accounts for the size of the markers
plus their bases (for example, for 14mm markers on 2mm bases, the Z-offset is
-9mm).
5. If you clicked Start, when you have selected the required markers, click the Stop
button.
In the 3D Perspective view the cameras shift as a group slightly along one or

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more rotation axes to better reflect an average of the markers scattered across
the floor, taking into account any offsets that you specified. The latest
calibration (.xcp) file is updated. This calibration file is automatically copied to
every subsequent trial captured.
Your Vicon cameras are now calibrated and ready to capture data.

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Manage camera calibrations
In the Manage Camera Calibration section of the System Preparation Tools pane, you
can click Auto number cameras to automatically number the cameras number in
ascending order, according to their position in the capture volume.
The Manage Camera Calibration section also enables you to reset or load camera
calibrations that define settings for Vicon cameras.
Automatically number cameras on page 105
Reset and load camera calibrations on page 107

Automatically number cameras
The Auto number cameras button enables you to quickly number the currently
connected Vicon cameras in ascending order, according to their position in the capture
volume. To obtain useful autonumbering, you normally auto-number the cameras at
some point after you have aimed (and calibrated) the cameras.

Tip
You can auto-number the cameras at any point after you have performed the
Aim Cameras operation (see Aim Vicon cameras on page 64): you do not
need to perform a complete camera calibration to auto-number the cameras.

Automatic numbering starts with the camera that is furthest from the volume origin.
The cameras are then numbered in a clockwise direction around the volume. If your
cameras are positioned at different levels, the cameras in the level that contains the
most cameras are numbered first.

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To automatically number Vicon cameras:
1. Ensure Nexus is in Live mode and that you have aimed the cameras.
2. On the System Resources tab, ensure you can see a list of Vicon cameras.

3. On the System Preparation Tools pane, in the Manage Camera Calibration
section, click Auto number cameras.
The cameras are automatically numbered in ascending order, according to their
position in the volume.

4. In the volume, check that the cameras are now numbered as required.

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Reset and load camera calibrations
During camera calibration, Vicon Nexus creates a calibration parameters (.xcp) file.
When you change the currently loaded .xcp file, either by calibrating cameras or by
setting the global coordinate system, Nexus stores the calibration state before the
changes. This enables you to revert to the previous calibration or load a different
calibration at any time while using Nexus (for example, you would normally want to
load a different calibration when you connect your Nexus PC to a different system).
Changing a camera calibration can be useful in the following circumstances:
To undo a poor calibration
To compare calibration changes
To manage camera calibration files in Nexus:
In the System Preparation Tools pane, under the Manage Camera Calibration section,
click the desired button:
Reset Removes all non-existing cameras, clears the calibrated position for existing
cameras, and reverts all calibration parameters to their default settings. This enables
you to recalibrate the system from a clean starting point.
Load Enables you to load a previously saved calibration file. In the Choose a file
dialog box, navigate to and select the desired camera calibration (.xcp or .cp file) and
click Open.
If a camera is not calibrating well or has been bumped after calibration, you can remove
it from the current calibration prior to data capture.
To remove a camera from an existing system calibration:
Use any of the following methods:
In the System Resources pane, right-click on the node for the camera you want to
remove and select Reset Calibration; or
In the System Resources pane, select the node for the camera you want to remove
and in the Properties pane, scroll down to the Calibration section and click Reset
Calibration; or
In a 3D Perspective view, right-click the camera that you want to remove and then
click Reset Calibration.

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Prepare a subject
After you have configured and calibrated your Vicon system, and prepared a data
management hierarchy in which to store your data, you can prepare the subject whose
motion is to be captured.
To start with, you may find it easiest to use the standard Plug-in Gait marker set and in
Vicon Nexus, create a subject that is based on one of the Vicon-supplied labeling
skeleton templates (VSTs), as described in the following topics. If you are planning on
processing your captured data with Plug-in Gait, then you must use one of the supplied
Plug-in Gait VST files. For more information, see Modeling with Plug-in Gait on page 185
.
Later, if required, you may want to create your own custom labeling skeleton template.
The labeling skeleton template that you use is determined by your particular
application and your marker set. For information on how to create a custom labeling
skeleton template, see Creating labeling skeleton templates (VSTs).
Having chosen your marker set, you can prepare the subject data in Nexus. To do this,
you use the Subjects Resources pane and the Subject Preparation Tools pane to create
a new subject from a template and to calibrate the labeling skeleton. These and other
procedures that you may find useful while creating and calibrating your labeling
skeleton are described in the following topics:
Create a new subject from a template on page 110
Calibrate a labeling skeleton on page 113
Correcting swapped labels on page 127
Manually label a trial on page 128
Work with pipelines on page 131

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If you have problems calibrating your labeling skeleton, also see Troubleshooting
labeling skeleton templates in Creating labeling skeleton templates (VSTs).

Important
A Nexus .vst file is used only to define the marker set and to enable Nexus to
perform automatic labeling. It is not a biomechanical model that will output
valid joint angles or other kinematic/kinetic variables. To derive valid
kinematics or kinetics, use either a predefined model (such as Vicon Plug-in
Gait, as described in this documentation) or create your own model with Vicon
BodyBuilder, MATLAB or Python.

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Create a new subject from a template
Before you calibrate a labeling skeleton, you must create a new subject node for your
subject. The following instructions explain how to create a new subject node in the
Subjects Resources tree, and base it on an existing Vicon labeling skeleton template (.

vst file) in the Subjects Resources pane.
Sample .vst files, including those for Plug-in Gait, are provided in the Nexus model
templates folder (by default, C:\Program Files (x86)\Vicon\Nexus2.#\ModelTemplates).
If you are using a standard Vicon marker set, you can base a new Subject node on one
of these templates. You subsequently scale the template to fit your particular subject
when you calibrate the labeling skeleton (.vsk file).
If you are not using a standard marker set, or need to modify a standard set, you will
need to create a custom labeling skeleton template. For more information, see Creating

labeling skeleton templates (VSTs) or contact Vicon Support.
To create a new subject based on a Vicon labeling skeleton template:
1. Ensure that you have created or opened a session in a database in which you
want to store the trial data, and that it is the active session (see Prepare a data
storage location on page 94).
2. In the Subjects Resources pane toolbar, click the Create a new Subject from a
Labeling Skeleton button.

A list of all Vicon labeling skeleton templates (.vst files) currently contained in
the Nexus ModelTemplates folder as well as a Browse link are displayed.

Tip
The supplied templates, whose names end in Ai, enable you to autolabel
static frames.

3. Select or browse to the desired .vst file. (For details of Plug-in Gait templates, see

Plug-in Gait models and templates in the Plug-in Gait Reference Guide.

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4. In the Enter Subject Name dialog box, specify the name for your new subject (of
no more than 32 characters) and click OK.
5. If you used the Browse link rather than selecting a .vst file from the list, the
Choose a Subject file dialog box is then displayed. Navigate to and select the . vst
file on which the Vicon labeling skeleton (.vsk file) is to be based.
The new subject node is added in alphabetical order to the Subjects Resources
tree. The node automatically includes any sub nodes and data for the elements
defined in the selected .vst file: Markers, Segments, Joints, and Model Outputs.

Tip
Marker names are displayed in gray if they are defined in the template
but the markers are not yet labeled.

6. In the Properties pane for the newly created subject, enter values for all the
measurements that are required for this template. For information on the
measurements required to run the supplied Plug-in Gait model, see Take subject
measurements for Plug-in Gait on page 191 .

Tip
Required measurements are highlighted in pink until you supply a value
for them; optional measurements are not highlighted. Note that these
measurements are required to run the relevant model; they do not
affect labeling.

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7. In the Subjects Resources pane, right-click the subject name and click Save
Subject.

Note
When you save a labeling skeleton (VSK), Vicon Nexus automatically
creates an accompanying .mp file, which is saved into the same folder
as the VSK. If required, you can import this data by running an Import MP
pipeline operation. This is only necessary in particular circumstances
(for example, if you are using Vicon BodyBuilder or Vicon Polygon), and
is not part of the normal Nexus workflow.

You can now place the appropriate marker set on your subject, (for information on
attaching the Plug-in Gait marker set, see Attach Plug-in Gait markers to a patient on
page 199 ) and calibrate its labeling skeleton (.vsk file).

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Calibrate a labeling skeleton
Calibrating a Vicon labeling skeleton (VSK) enables Nexus to recognize the subject and
automatically determine which labels belong to its reconstructions.
Having chosen a labeling skeleton template (VST) for your subject (see Create a new
subject from a template on page 110), you then capture a short subject calibration trial
(see below), run the required calibration operations on it and save the trial and the
labeling skeleton (VSK). The calibration process applies the general information
contained in the VST to your particular subject, who is wearing the marker set
described in the VST. When you save the calibration, a labeling skeleton (VSK),
containing information that is specific to your particular subject is saved.
You can then use that VSK to automatically label all the trials in an entire capture
session. You only need to recalibrate if the subject changes, for example, if a different
subject wears the same marker set, or if the markers are moved. For more detailed
information about VSKs and labeling skeleton templates (VSTs) see Creating labeling

skeleton templates (VSTs) .
Nexus provides a number of processes and multiple calibration options for calibrating a
labeling skeleton. The factors that affect which process and which options are best for
your situation, include:
Whether your subject is able to perform a full ROM (Range of Motion) trial
The type of movement you are studying
Whether obtaining results quickly or labeling accuracy is more important
The following types of trial can be used to calibrate a labeling skeleton:
ROM trial In a ROM trial, the subject completes a series of movements that exercises
all of their joints. To produce the best calibration (and auto-labeling), the subject
moves all of their joints through as full a joint range as possible. For the best results,
ensure that each joint moves through a range that represents what the subject is
likely to do during capture of trial data (ie, movement trials). Full ROM calibrations
provide the most information of any of the calibration methods and therefore often
provide the best labeling. For this reason Vicon recommends using a full ROM
calibration whenever possible.
For step-by-step instructions on using this type of trial to calibrate a labeling
skeleton, see Calibrate a labeling skeleton using a ROM trial on page 115.
Static trial This is a short trial where the subject stands in a base pose. A base pose is
a static pose that is used when the VST (labeling skeleton template) file is first
created. For Plug-in Gait, this is a T-pose or 'motorbike' pose. (To view images of the

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motorbike pose, see Calibrate a labeling skeleton using a ROM trial on page 115.)
This operation requires the least processing time, but provides less information than
functional calibration (which is often used as part of ROM calibration, described
above), as it operates on only a single frame of data. Consider using this type of
calibration if:
A subject's ability to perform a ROM trial is limited; and/or
You want to obtain results as quickly as possible.
For step-by-step instructions on using this type of trial to calibrate a labeling
skeleton, see Calibrate a labeling skeleton using a static trial on page 125.
Movement trial This trial type is similar to a ROM trial, but focuses on only joint
movements that are expected and specific to the activity being studied. For example,
a gait laboratory might use a walking trial for this type of calibration. Movement trials
are not normally used for an initial or full subject setup, but can be used in
combination with some pipeline operations to improve labeling. They may be of
benefit if the motion of the subject during movement trials is not similar enough to
what is captured when using a static or ROM trial. For more information on this type
of labeling skeleton calibration, see Labeling skeleton calibration in detail in the

Vicon Nexus Reference Guide.
Whichever type of calibration you choose, note the following requirements for your
calibration trial:
Aim to produce a trial (ROM, static, or movement) that is as fully labeled as possible.
The trial must contain only raw reconstructions; leave any gaps unfilled. (Unlabeled
reconstructions have no influence on subsequent operations.) However, if necessary,
you can manually label any missing markers (see Manually label a trial on page 128)
or correct any swapped markers (see Correcting swapped labels on page 127).
For information on creating custom labeling skeleton templates (VSTs), see Creating

labeling skeleton templates (VSTs) .

Note
This topic assumes that you are using a Vicon-supplied PlugInGait Ai VST,
although you could instead use a custom VST, providing it conforms to the
requirements listed in Requirements for custom labeling skeleton templates in

Creating labeling skeleton templates (VSTs).

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Calibrate a labeling skeleton using a ROM trial
The recommended workflow for Nexus 2, which is described below, is to use a ROM
trial and dynamic calibration to calibrate a labeling skeleton, as this is likely to produce
more accurate automated labeling. However, if you need to use a static frame to
calibrate your labeling skeleton (for example, if your subject cannot perform a full ROM,
or you are capturing simple movement and/or want to obtain some results quickly), see
Calibrate a labeling skeleton using a static trial on page 125.
After you have prepared a subject for capture (see Prepare a subject on page 108), to
enable Nexus to provide correct automatic labeling for your subject, you capture a
ROM (Range of Motion) trial that starts with a few frames where the subject is static,
as described in the following steps.
Vicon Nexus then uses the information from the ROM trial to automatically label the
subject in subsequent movement trials.
The following workflow is just one approach that you can adapt to suit your particular
circumstances. For a detailed explanation of all the methods of subject calibration, see
Labeling skeleton calibration in detail in the Vicon Nexus Reference Guide.
The workflow for calibrating a labeling skeleton based on a ROM trial can be divided
into the following stages:

Perform an initial calibration of a labeling skeleton using a ROM trial
1. Ensure you have obtained any subject measurements required to run the model
(required measurements are highlighted in pink in the Subjects Resources pane):
for Plug-in Gait Lower Body, these are the body weight and height as well as
measurements of both left and right leg lengths, knee widths, and ankle widths.
These are used to calculate joint center positions, and must be measured and
entered into Nexus before any modeling can take place can begin. Optionally,
you can also measure tibial torsion, the inter-ASIS distance, the ASIS-to-greater
trochanter distance, and the sole delta if the subject is wearing shoes. For more
information on the measurements needed to run the Plug-in Gait model, see
Take subject measurements for Plug-in Gait on page 191.
2. In the Communications pane, on the Data Management tab, ensure that you
have created or opened the required database in which to store the data you will
be capturing and that the required session is active. (For a reminder of how to do
this, see Prepare a data storage location on page 94.)
3. In the Resources pane, ensure Nexus is in Live mode.

4.
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4. In the System Resources tree, select the Local Vicon System node and then in
the Properties section under General, check that the Processing Level, which
sets the amount of real-time processing that is performed on the source data, is
set appropriately. If you are not sure, set it to at least the Labels level.
5. Display a 3D Perspective view.
6. In the Subjects Resources tree, ensure the required PlugInGait Ai (Auto Initialize)
labeling skeleton template (VST) file is specified for the subject (see Create a
new subject from a template on page 110) and that the subject node you
created from the template is the only entry enabled for capture. (When enabled,
the check box contains a check mark.)
7. If required by your model, in the Properties section at the bottom of the Subjects
Resources pane, enter any subject measurements you obtained in step 1.
8. In the Subject Preparation Tools pane, ensure that the subject you created is
selected in the Subject list.

Tip
If you want to capture video or if you want to avoid automatically
switching to Offline mode as soon as you have captured a trial, instead
of clicking the Subject Preparation button, click the Capture button and
on the Capture tab, ensure the settings are as required (for example, to
capture video, ensure that in the Data Source Setup section, Video
Camera Data is selected).

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9. To enable Nexus to automatically label the key trajectories, in the capture
volume, have the subject stand in the stationary neutral pose that was selected
when the labeling skeleton template was created. If you are using a Viconsupplied PiG template, ensure the pose is as described in step 12.

Tip
To help you to ensure that the subject adopts the correct base pose, on
the view pane toolbar, click the Split vertically button and in the second
pane, open a Subject Viewer. This displays the base pose for the current
labeling skeleton template (VST).

10. To make sure all the markers are visible, count the number of markers under the
Markers node in the Subjects Resources tree, and make sure the same number of
markers is visible in the 3D Perspective view.
11. On the Capture Tools pane, in the Capture section, click Start.
The Start button switches to its Stop setting.
12. Capture a ROM trial where the first 1–3 seconds are of the subject in the
'motorbike' pose, as shown in the following image, in which:
Arms are outstretched, held level or slightly lowered, with elbows bent and
further forward than the shoulders (so that they don't hide any of the body
markers).
Rest of body is straight.
Feet point forward

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For the rest of the ROM trial, have the subject go through the required range of
motion.

Tip
If the subject is not able to attain the base pose, they can use any pose
where all of the markers are visible to the cameras. This ensures that
the markers can be reconstructed, but is unlikely to produce good
autolabeling when Autolabel Static Frame (part of the Auto Initialize
Labeling pipeline) is run. If this is the case, you will need to manually
label the trial (see Manually label a trial on page 128) and then run the
two remaining operations from the Auto Initialize Labeling pipeline. (For
information on running pipelines, see Run a pipeline on page 132.)
If the chosen base pose proves unattainable by many subjects, consider
substituting a different, attainable pose by specifying a different frame.
To do this, on the Pipeline Tools pane, expand the Subject Calibration
section and double-click the Set Autolabel Pose pipeline operation to
add it to the current pipeline. In the Properties pane, ensure the frame
with the required pose is selected and then run the Set Autolabel Pose
pipeline.

13. When enough data has been captured, click Stop to end the trial. For a ROM trial,
this is typically 1–3 seconds of static data capture, followed by the required ROM.
If you are using the Subject Preparation tab, Nexus automatically switches to
Offline mode.

14.
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14. Reconstruct the trial either by clicking Reconstruct

on the Nexus toolbar or,

if you need to change the reconstruction settings, by clicking the Pipeline button
in the Tools pane and configuring and running the Reconstruct pipeline to
create a 3D image of the captured markers. (For information on how to run a
pipeline, see Run a pipeline on page 132.)
15. View the subject data in a 3D Perspective view and ensure that all the markers
are clearly visible to the Vicon cameras. (If they are not, check your camera
settings, system setup steps, system calibration, etc. Also check that clothing
isn't causing markers to move, and the condition (age, etc) of the markers
themselves.)
16. From the Pipeline Tools pane, run the supplied Auto Initialize Labeling pipeline
(or if preferred, you can manually label the trial):

17. Nexus labels the trajectories based on the marker set defined in the . vst file.
18. Save the trial and the labeling skeleton (VSK) by pressing CTRL+S or by clicking
the Save button

on the Nexus toolbar. If an asterisk is displayed to the right

of the the subject name in the Subjects Resources pane, this means that you
have also made changes that affect the labeling skeleton template (VST).To save
the VST, right-click on the subject name and click Save Subject.

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Review and finalize a calibration of a labeling skeleton using a ROM trial
1. After you have saved your initial calibration (see above), assess the results by
looking at the labeling of the frame that contains the static base pose in the 3D
Perspective view. Ensure that all markers are connected by sticks and that the
sticks on the left side of the subject are red and those on the right side are
green. For a more detailed check, look at the information on the data Quality tab.

Tip
To see all the assigned marker labels in the 3D Perspective view, press
CTRL+space bar. This enables you to check that all the required markers
are present and correctly labeled.

2. Depending on the results of the labeling, take the appropriate action:
If the static frame is correctly labeled and the labeling skeleton fits well, any
further processing of your first movement trial (see Capture movement trials
on page 136) will give you an indication of the level of labeling that this
subject calibration will provide for your specific trial type. Based on these

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results, you can decide whether they meet your requirements. For example, for
walking trials, the quick calibration produced by the Auto Initialize Labeling
pipeline is likely to produce good labeling of movement trials.
When the subject has been calibrated, segments of the labeling skeleton are
fitted to the labeled markers in the 3D Perspective view, and your subject is
automatically labeled. To verify that the subject has been calibrated
successfully, switch Nexus to Live and ask your subject to move around in the
capture volume. You should see that the markers are labeled and the subject is
tracked.
If the results are satisfactory, go straight to step 4(set a range).
If the results are not satisfactory, this may be because your movement trials
include more challenging or complex movement and therefore require a
further level of labeling reliability. To provide this enhanced reliability you will
need to run a functional calibration, which calibrates the subject's bone
lengths and joint and marker locations from the whole ROM trial, as described
in step 3. To ensure the best results, first consider the following factors:
If any markers are labeled incorrectly, fix them (see Correcting swapped
labels on page 127 and Manually label a trial on page 128) and from the
Auto Initialize Labeling pipeline, re-run the Scale subject and Marker-only
Subject Calibration operations; or
If all the labels are correct but there is a large distance between a marker
and the corresponding reconstruction, the labeling skeleton cannot
accurately represent the configuration of labeled reconstructions. This is an
indication that you may get poor labeling results and may need to improve
your labeling skeleton template (see Requirements for custom labeling
skeleton templates in Creating labeling skeleton templates (VSTs)).
Note that Functional Skeleton Calibration takes more processing time to
complete than the Auto Initialize Labeling pipeline.
3. (Optional step) Run a Functional Skeleton Calibration by completing the
following steps:
a. Verify that the trial is correctly labeled for every frame.
Note that Autolabel Static Frame only labels the trajectories that are
present on the static frame(s).
b. Visually check for any markers that get occluded and manually re-label
them (see Manually label a trial on page 128) when they re-appear.
c. On the Pipeline Tools pane, expand the Subject Calibration operations
section, add the Functional Skeleton Calibration operation to the current
pipeline and run it.

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c.

d. When the Functional Skeleton Calibration has completed, in the Options
dialog box (F7), click Subjects (on the left) and in the Properties pane, go
to the Markers section, and select Draw Covariance.
If you can see any large covariance ellipsoids around a marker, check for
mis-labeling of a small number of frames for that marker and fix any
mislabels. Note that some markers, such as the ASIS markers, will naturally
have a larger covariance, due to skin motion.

Tip
The size of covariance ellipsoids vary, depending upon the way a
marker is defined in a skeleton, the amount of marker movement
possible, and the quality of the subject calibration. Particularly
large covariance ellipsoids may indicate a poor calibration.

4. On the Time Bar, move the Start Range indicator and End Range indicator (the
blue triangles) along the timeline to set a range of frames to select only the first
few seconds of the static pose at the beginning of the trial.
5. Run any further processing needed to achieve the required modeling. For
example, if you are using Plug-in Gait, to make the necessary calculations and
calibrate the static subject, run the Plug-in Gait Static pipeline:
a.
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a. In the Current Pipeline list, select the Plug-in Gait Static pipeline, and
ensure that you leave the check box for Processing Static Subject
Calibration cleared (its default setting).

b. Click on the Process Static Plugin Gait Model operation and ensure that in
the Properties pane, the First Frame is set to Selected Start and Last
Frame is set to Selected End (the default settings).
c. Run the Plug-in Gait Static pipeline.
6. To check that your model has been processed correctly:
Ensure that in the Pipeline Tools pane, a green check mark is displayed to the
left of the operation in the Current Pipeline list.
Ensure that Plug-in Gait bones are visible in the 3D Perspective view. If they
are not, press F7 to open the Options dialog box and select Plug-in Gait Bones.
In the Subjects Resources pane, ensure that you can expand Model Outputs to
see all the calculated components of variables for a kinematic model (such as
Angles, Forces, Moments, etc).
To verify that Nexus has successfully created a labeling skeleton and that it is
automatically labeling, ensure that, as shown in the following image, the
bounding boxes for Plug-in Gait model segments are displayed in the 3D
Perspective view. (The bounding boxes that Nexus draws around each
segment that is defined in the template are for visualization purposes only.)

7.
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7. Save the ROM trial and the labeling skeleton (VSK) by pressing CTRL+S or
clicking the Save button

on the Nexus toolbar.

When you have a fully labeled and processed trial (containing only raw reconstructions
and no gap-filling), you can proceed to capture and process your movement trials (see
Capture movement trials on page 136).

Tip
To save time in future, you may want to save all the relevant pipeline
operations to one customized pipeline. To do this, add the relevant operations
to the end of the Auto Initialize Labeling pipeline and save the pipeline under
a new name.

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Calibrate a labeling skeleton using a static trial
The recommended workflow for Nexus 2 is to use a ROM trial and dynamic calibration
as this offers the benefits of the more efficient, automated labeler (for more
information on this workflow, see Calibrate a labeling skeleton using a ROM trial on
page 115). However, if you need to use a static frame to calibrate your labeling
skeleton (for example, if you are capturing simple movement, or your subject cannot
perform a full ROM, and/or you want to obtain some results quickly), you can instead
use the following workflow.
To perform a static calibration:
1. Ensure you have obtained and entered any subject measurements required to
run the model (required measurements are highlighted in red in the Subjects
Resources pane): for Plug-in Gait, these are the body weight and height as well
as measurements of both left and right leg lengths, knee widths, and ankle
widths. These are used to calculate joint center positions, and must be measured
and entered into Nexus before any processing can begin. Optionally, you can also
measure tibial torsion, the inter-ASIS distance, the ASIS-to-greater trochanter
distance, and the sole delta if the subject is wearing shoes.
2. In the Communications pane, on the Data Management tab, ensure that you
have created or opened the required database in which to store the data you will
be capturing and that the required session is active. (For a reminder of how to do
this, see Prepare a data storage location on page 94.)
3. In the Resources pane, ensure Nexus is in Live mode.
4. Display a 3D Perspective view.
5. Capture a static trial. For more details, see Perform an initial calibration of a
labeling skeleton using a ROM trial on page 115.
6. Reconstruct the trial either by clicking Reconstruct on the Nexus toolbar or, if
you need to configure the reconstruction settings, by clicking the Pipeline
button

in the Tools pane and changing and running the Reconstruct pipeline

to create a 3D image of the captured markers. (For information on how to run a
pipeline, see Run a pipeline on page 132.)

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In the Subjects Resources tree, right-click on the subject node and attach the
required PlugInGait Ai (Auto Initialize) labeling skeleton template (VST) file (see
Create a new subject from a template on page 110) to the subject.

Tip
To use a workflow prior to Nexus 2.x, ensure you use the required old
labeling skeleton template, (PlugInGait.vst, PlugInGait Fullbody.vst, etc).
If you chose to import old settings files when you first installed Nexus 2.
x, you can select it from the list of available templates. If you didn't
import the old settings files when you installed Nexus 2, copy the old
VST files from ...\Vicon\Nexus\ModelTemplates to ...\Vicon\Nexus2.
#\ModelTemplates.

7. Ensure that the subject node is the only entry enabled for capture. (When
enabled, there is a check mark in the check box.)
8. In the Pipeline tools pane, select and run the Auto Initialize Labeling pipeline or if
necessary, manually label the trial (see Manually label a trial on page 128).
Nexus labels the trajectories based on the marker set defined in the . vst file.
9. Assess the results by looking at the labeling in the 3D Perspective view. Ensure
that all markers are connected by sticks and that the sticks on the left side of the
subject are red and those on the right side are green.
10. Save the trial and the labeling skeleton (VSK) by pressing CTRL+S or clicking the
Save button

on the Nexus toolbar.

11. You can now run any further processing needed to achieve the required
modeling and finalize the calibration (see steps 5–7 of Review and finalize a
calibration of a labeling skeleton using a ROM trial on page 120).
When you have saved a fully labeled trial (containing only raw reconstructions and no
gap-filling), you can proceed to capture and process your movement trials (see Capture
movement trials on page 136).

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Correcting swapped labels
To obtain error-free auto-labeling, it is very important to ensure that the labels are
present and correct in your .vst file and that you have labeled your ROM or static trial
before running any calibration operation. If the markers in your ROM or static trial are
not labeled, the calibration operation will fail. If your markers are erroneously labeled
(for example, if left and right markers have been mistakenly swapped) the operation will
succeed, but when the Vicon Skeleton (.vsk file) is used for automatic marker labeling
of your movement trials, it will continue to produce the erroneous labels.
To address this, check your labeling carefully. If you identify any swapped markers, you
can correct this using the Swap Marker Labels button in the Label/Edit Tools pane.

Tip
To see all the assigned marker labels in the 3D Perspective view, press
CTRL+space bar.

To correct swapped markers:
1. Select the two swapped markers in either the 3D Perspective view or in the
Subjects Resources pane.
2. In the Label/Edit Tools pane, in the Manual Labeling section, click the Swap
Marker Labels button.

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Manually label a trial
The recommended workflow for Nexus 2 is to use a ROM trial and dynamic calibration
as this enables the use of automated labeling (for more information on this workflow,
see Calibrate a labeling skeleton using a ROM trial on page 115). However, on
occasions, you may need to supplement automated labeling with manual labeling, or to
use manual labeling where automated labeling gives insufficiently accurate results.
You manually label reconstructed trial data using the tools in the Label/Edit Tools pane.
Manual labeling involves associating the markers defined in a Vicon labeling skeleton
template (.vst file) with reconstructed markers displayed in the 3D Perspective view.
The manual labeling is then used when the .vst file is scaled to fit the subject wearing
the marker set described in the .vst file, during subject calibration. In subsequent
movement trials, Nexus uses the resulting subject-specific Vicon labeling skeleton (.vsk
file) to automatically label the subject wearing the same marker set.

Important
Before manually labeling markers, ensure that you have already:
Created or opened a session in the database on page 94 in which you
want to store the trial data, and ensured that it is the active session.
Obtained an existing .vst on page 108 file corresponding to the type of
subject whose motion is to be captured, or created a custom Vicon labeling
skeleton template.
Created a new subject node on page 110 from the template in which the
manual labeling is to be stored.
Attached the Vicon markers to the subject in accordance with the marker
set defined in the associated template. For information on how to do this for
Plug-in Gait markers, see Attach Plug-in Gait markers to a patient on page
199.
Captured a brief ROM trial including static frames on page 115, or a static
trial on page 125, or obtained a single frame of live data with reconstructed
markers corresponding to the marker set specified in the associated .vst file.

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To manually label 3D marker reconstructions:
1. In the Communications pane, on the Data Management tab, open the trial file
that contains reconstructed markers.
2. On the time bar, move the current time indicator (vertical blue line) to the first
frame of the trial in which the subject is standing in a stationary neutral pose.
This is typically a T-pose or 'motorbike' pose, in which the subject stands in the
basic neutral pose and raises the arms out straight to the sides with palms facing
down in a position in the shape of a T. If the subject is not able to attain the Tpose, they can use any neutral pose where all of the markers are visible to the
cameras so that they will be able to be reconstructed.
3. In the Subjects Resources tree, ensure that the subject node you created from
the template is the only entry enabled for capture. (When enabled, there is a
check mark in the check box.)
4. At the top of the Label/Edit Tools pane, from the Subject list select the subject
to be manually labeled.
Labels for the markers defined in the .vst file are displayed in the list in the
Manual Labeling section.
5. By default, the Whole button is selected, so trajectories are labeled in both
directions. This ensures that, when you label a marker at the current frame, the
same marker is labeled throughout the trial. However, if you want the marker to
be labeled from this point forward (or backward) only, for example, if you are
resolving an overlapping trajectory, click the Backward or Forward button before
proceeding.
6. In the Manual Labeling section, ensure Auto advance selection is selected to
have Nexus automatically select the next label in the list after you have assigned
a label to a marker.
7. In the list in the Manual Labeling section, click on the label you want to use.
The shape of the pointer changes to include a tooltip that identifies the selected
label to guide you in assigning labels to markers in the 3D Perspective view.

Tip
To help you apply labels to the correct markers, on the view pane
toolbar, click the Split vertically button and in the second pane, open a
Subject Viewer. Any marker you select in the Label/Edit Tools pane is
highlighted in the Subject Viewer, so that you can see where to place it
on the figure in the 3D view.

8.
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8. In the 3D Perspective view click on the marker to which you want to assign the
label.
The next label in the list is selected and the tooltip changes to indicate that
label. As you label more markers, a colored line is drawn between each marker
until a stick figure appears.

Tip
If you move the mouse to another area of the Nexus workspace while a
marker is selected in the Manual Labeling section, the cursor retains the
tooltip, indicating that Nexus is still in labeling mode. If you need to do
something else in Nexus before marker labeling is complete, you can
turn off labeling mode in one of these ways:
Press the ESC key.
Click on the Label/Edit icon, or any of the other icons in the Tools
pane toolbar.

9. Repeat steps 7-8 until you have assigned all of the labels to markers.
The stick figure in the 3D Perspective view should resemble a skeleton of the
subject type defined in the .vst file.
10. To verify that the manual labeling was successful, check that all the markers are
connected by sticks and that the sticks on the left side of the subject are red and
those on the right side are green.

Tip
To find the next unlabeled marker in the clip, you can also use the Find
Next Unlabeled Trajectory button. Nexus searches from the current
frame forward until it finds an unlabeled marker. When found, the
marker is selected and centered in the view pane.

11. To save the labeling information with the trial, on the Nexus toolbar, click the
Save button.

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Work with pipelines
Pipelines enable you run one or more operations that you use frequently or on a large
number of trials, from import, through reconstruction and labeling and various other
types of processing, to export.
You can set up pipelines to run automatically immediately after capture or as required
on one or more saved trials.
You can use any of the pipelines supplied with Vicon Nexus or create your own by
grouping a particular sequence of operations to suit your particular needs. Each
operation within a pipeline can have a unique set of options and parameters.

Tip
If you are working with large numbers of files, to further speed up your work,
you can set up and run pipelines as batch processes, using Show File Transfer
/Batch Processing interface

and then the Batch Processing button

on the Data Management tab.

The following topics describe how to:
Run a pipeline on page 132
Create a pipeline on page 134

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Run a pipeline
This topic describes how to run a pipeline. For information on creating your own
pipelines, see Create a pipeline on page 134.
The procedure for running a pipeline is the same, whether you want to run a pipeline
supplied with Vicon Nexus or your own custom pipeline.
To run a pipeline:
1. In the Subjects Resources pane, ensure that the subject whose trial data you
want the pipeline to operate on is enabled. (When a subject is enabled, there is a
check mark in the check box next to it.)

2. If you want the pipeline to operate only on a part of the trial rather than the
whole trial, on the time bar, move the blue triangles that represent the start and
end of a range of frames along the time line to set the required range.

Tip
To change the view of the timeline so that it shows only the selected
range, right-click on the timebar and then click Zoom to Region-ofInterest.

3. In the Pipeline Tools pane, from the Current Pipeline list, select a pipeline.

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4. In the Current Pipeline operations list, ensure that the operation(s) to be run is
selected.

5. Click the Run button to start the pipeline process. Each operation is run in the
order it appears in the list from top to bottom.
The progress bar displays the results of the pipeline processing, and gives an
indication of the percentage of processing completed for each operation.

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The Current Pipeline operations list may contain the following information for
each operation (to the right of the check box):
Processing The operation is being processed.
Processed The operation was completed successfully.
Failed The operation was not completed successfully.
Stopped The operation processing was stopped.

Create a pipeline
To save time, you can save and run sequences of frequently used processing operations
using tools in the Pipeline Tools pane. Some pipelines can also be selected and run in
the Subject Preparation Tools pane and the Capture Tools pane.
The following instructions describe how to create your own pipeline. For information
on how to run an existing pipeline, see Run a pipeline on page 132.
To create a pipeline:
1. If you want to modify an existing pipeline, in the Pipeline Tools pane, in the
Current Pipeline area, select an existing pipeline. If you want to create a new
pipeline, go straight to the next step.
2. In the Available Operations list, expand or collapse the pipeline type to display or
hide the operations you can use for that type of automatic processing of trial
data:
File Import Operations for automating the import of trial files into Vicon Nexus
from third-party software packages.
Core Processing Operations for automating reconstruction, labeling, and
kinematic fitting to produce 3D trajectories from raw marker data.
Subject Calibration Operations for automating the processing of system and
labeling skeleton calibration.
Events & Timebar Operations for automating events and operations that can
be carried out using the timebar.
Fill Gaps & Filter Data Operations for automating the post-processing of data,
such as gap-filling and data-filtering.
Data Processing Operations for automating the production of model outputs
(forces and moments, joint angles, etc).
File Export Operations for automating the export of trial files from Vicon Nexus
to third-party software packages.

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System Operations for automating offline camera calibration, applying a codec
to video, resetting force plate offsets and setting the camera calibration origin.
Legacy Operations for automating access to legacy labeling and fit motion.
For further details of each of the pipeline operations, see Pipeline tools in the

VIcon Nexus Reference Guide.
To view a tooltip describing an operation's function, hover the pointer over its
name in the list.
3. Double-click each operation that you want to include in your pipeline.
The operation is displayed in the list in the Current Pipeline section. The
operations are run in the order they appear in the pipeline; to rearrange the
order, drag operations into the required position in the list.

Tip
To automatically save the trial you are processing, add the Save Trial C3D + VSK operation (located in the File Export pipeline operations) to
your pipeline. As a general rule, you will want to save the trial as a last
step after the other pipeline operations have been run, so position the
Save Trial - C3D + VSK operation at the required point in the Current
Pipeline operation list.

4. In the Current Pipeline list of operations, click on the operation you added in the
previous step, then in the Properties pane at the bottom of the Pipeline Tools
pane, view or change the settings as required.
5. To save your pipeline settings to a .pipelines file in the Pipelines folder (see
Manage system configurations on page 21), click the Save button to the right
of the Current Pipeline list.
6. In the Save As dialog box, supply a name for your new pipeline.
An asterisk * is displayed next to the pipeline name if there are unsaved changes.

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Capture movement trials
Before you collect your trial data, you must first have calibrated the labeling skeleton
(see Calibrate a labeling skeleton on page 113) and ensured your subject is wearing the
appropriate marker set.
When you have calibrated the labeling skeleton, you are ready to capture movement
trials for the specified subject, during which the patient performs the motion that is to
be analyzed. You then reconstruct and label the trial data, and run any further
processing required.
For detailed instructions on these steps, see:
Capture the required movement on page 137
Reconstruct and label movement trials on page 150
You capture motion data using the tools in the Capture Tools pane, and process trial
data using tools on the Nexus menu bar or in the Pipeline Tools pane.

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Capture the required movement
After you have calibrated the labeling skeleton for your subject (see Calibrate a labeling
skeleton on page 113), you can capture the required trials.
You can stream motion data in real time and/or capture raw camera data for offline
processing. You can capture a trial manually (see below), or configure Nexus to start
/stop capture automatically (see Automatically start and stop capture on page 140).
To quickly capture sequences of trials using the same setup information for each trial,
see Use Simple Capture Mode on page 148.

Note
For clarity, reconstruction and labeling are described as separate steps.
However, if you want to run reconstruction and labeling as soon as each trial
has been captured, you can add these operations (and any others that you
want to run automatically) to a post-capture pipeline that runs as soon as
capture finishes. For more information see step 7 below.

Before capturing a movement trial, ensure that you have already:
Created or opened a session in the database in which you want to store the trial data,
and ensured that it is the active session. For more information, see Prepare a data
management hierarchy to store your files on page 94.
Loaded an existing .vsk file for the subject whose motion is to be captured. If you
have just created your VSK (see Calibrate a labeling skeleton on page 113), the
correct VSK is already loaded. If not, in the Subjects Resources pane, click the Load
an existing subject button

and open the required .vsk file.

Attached the Vicon markers to the subject in accordance with the marker
arrangement used in the labeling skeleton (.vsk) file (if you are using Plug-in Gait, see
Attach Plug-in Gait markers to a patient on page 199).

Tip
If you are using Plug-in Gait, Vicon recommends that you do not remove the
heel markers for the movement trials. Their presence does not affect the
calculated output from Plug-in Gait, but it does improve the reliability of the
automatic labeling in Nexus.

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To capture movement trials:
1. In the Resources pane, ensure Nexus is in Live mode.
2. Display a 3D Perspective view.
3. In the Capture Tools pane, select an existing capture configuration for the trial
from the Trial Type list or save as a new one.

4. In the Next Trial Setup section, complete the details for storing your trial data in
the active session.
In the Data Source Setup section, ensure Optical Camera Data,Video Camera
Data, and Device Data are selected as required.
5. If you want capture to start and/or stop automatically, specify the required
settings in the Auto Capture Setup section. (For more information, see
Automatically start and stop capture on page 140.)
6. If you are conducting clinical gait trials for kinetic analysis involving one or more
force plates and want Nexus to automatically assess whether the foot is
correctly positioned and is producing valid data for your live trials, ensure that in
the Options dialog box (F7), Footstrikes is selected. For more information, see
Automatically assess foot strikes on page 146.
7. In the Post-Capture Pipeline Setup section, specify any pipelines containing
operations to be run automatically on the trial data when the capture is
complete. (For example, if you are using Plug-in Gait, you could select Run
pipeline after capture and then select the Reconstruct And Label and Plug-in
Gait Dynamic pipelines. This automatically reconstructs and labels the data and
then runs filtering, event detection, modeling and export operations.) However,
to start with, you will probably prefer to leave this option cleared, so that you can
run each operation separately and observe their effects.
8. In the System Resources tree, select Local Vicon System and then in the
Properties pane, in the General section, set Processing Output Level to Labels.
9. In the capture volume, have the subject perform the movement that is to be
captured.

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Nexus automatically reconstructs, labels, and fits the Vicon labeling skeleton
created in the previous stage (see Prepare a subject on page 108) to the subject
in real time.

Tip
If a labeling error is obvious or persistent, restart the labeler by rightclicking Local Vicon System node and then clicking Reboot Core
Processor (CTRL+R).

If the subject steps on the force plates, the force vector is also shown in real
time.
10. On the Capture Tools tab, unless you have specified a time or trigger on which to
start capturing (see step 5), in the Capture section, click Start to begin capturing
and in the capture volume, have your subject wearing the appropriate marker set
for your VST perform the required motion.
11. Unless you have specified a time or trigger on which to stop capturing in the
Auto Capture Setup section, when the subject has completed the required
motion, click Stop.
If you specified a post-capture pipeline (see step 7), Nexus automatically
switches to Offline mode, displays the subject data in the 3D Perspective view,
and automatically performs any operations contained in any pipelines selected in
the Post-Capture Pipeline Setup section. Otherwise the system remains Live,
ready to capture the next trial.

Tip
If events are not automatically detected, or are only partially detected,
you will need to add them manually (see Add events to trials on page
180). You will probably need to do this in situations such as: trials
without force plates; movements that are not on a flat surface, such as
stepping up/down/over, climbing, etc; pathological or non-cyclical gait
movement.

12. Repeat steps 9–11 until you have obtained the required number of trials.
You can now reconstruct and label the trials. For more information, see Reconstruct
and label movement trials on page 150.

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Automatically start and stop capture
If required, instead of having to manually start and stop capture (see Capture the
required movemen on page 137t), you can trigger data capture using an external
device or based on a specified period of time.
You can configure Vicon Nexus to automate data capture using the following options:
Automatically record data before capture is triggered on page 140
Stop data capture after elapsed time on page 141
Trigger data capture on labeling percentage on page 141
Trigger data capture using a remote control device on page 143
Trigger data capture using timecode on page 143
Trigger data capture over a network on page 145

Automatically record data before capture is triggered
The Capture before start option enables you to specify the number of seconds of data
to record prior to capture being triggered either manually (with the Start button) or
automatically (based on timecode or a remote control device).
To automatically record before capture is triggered:
1. Ensure you have prepared for capture as described in Capture the required
movement on page 137, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup, select Capture Before
Start (secs) and specify the number of seconds to record data prior to capture
being triggered.
3. Trigger the capture manually or using one of the remote capture methods
described in this section.
The Vicon cameras capture the subject moving in the capture volume.
4. Stop the capture manually or using one of the remote capture methods
described in this section.
Nexus automatically switches to Offline mode and displays the subject data in
the 3D Perspective view.

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Stop data capture after elapsed time
The Stop after duration (secs) option enables you to specify a time period after which
Nexus is to automatically stop a capture.
To stop data capture after a specified time period:
1. Ensure you have prepared for capture as described in Capture the required
movement on page 137, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup, select Stop After
Duration (secs) and specify the number of seconds after which to automatically
stop motion capture.
3. Capture a trial manually or using one of the remote capture methods described
in this section.
The Vicon cameras capture the subject moving in the capture volume. Nexus
automatically stops the capture after the specified number of seconds,
automatically switches to Offline mode, and displays the subject data in the 3D
Perspective view.

Trigger data capture on labeling percentage
With the Start on Labeling (%) option selected, captures automatically start when a
subject first fully enters the volume. If the Stop on Labeling % option is also selected,
captures automatically stop when the subject leaves the volume.
You can set the labeling percentage (ie, the percentage of markers expected from the
total number of markers in your subject's labeling skeleton) that needs to be
recognized by Nexus within the capture volume for the subject to be considered as
fully in the volume or to have left the volume and therefore to trigger capture start
/stop.
The following procedure describes how to set up data capture to automatically crop
live trials, based on labeling percentages. For information on how to automatically crop
trials that you have already saved based on labeling percentages, see Crop trials on
page 165.
1. Ensure you have prepared for capture as described in Capture the required
movement on page 137, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup and select Start on
Labeling (%) and/or Stop on Labeling (%).

3.
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3. The default values for this operation start capture when at least 90% of a
subject's markers are recognized and stop when less than 65% remain (volume
exit). You can adjust these percentages to suit your capture type.

4. Have a subject wearing the required marker set enter the volume.

Tip
To check data quality, you can display the labeling percentage by
selecting the subject and in a Graph view choosing Labeling to show
how many labels are present on each frame.

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Trigger data capture using a remote control device
The Start/Stop on remote trigger option enables you to use an external remote control
device to trigger data capture. The remote control device must be connected to a
Vicon Lock+ or an MX Giganet in your Vicon system (for details, see either the Vicon

Vantage Reference Guide or Go Further with Vicon MX T-Series), and the sync outputs
(GPO pins) for the remote functionality must be configured under the Vicon Lock or MX
Giganet node in the System Resources pane.
To trigger data capture using a remote control device:
1. Ensure you have prepared for capture as described in steps 1–4 of Capture the
required movement on page 137.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced
options are displayed, and select Start/Stop On Remote Trigger.
3. To set the system to a state where it is ready to accept a trigger signal for
automatic capture based on a remote control device, click the Arm button.
If you want to enable the system to remain ready to receive subsequent remote
capture signals after the capture is stopped, click the Lock button to the right of
the Arm button.
4. Trigger the start of the capture from your remote control device.
The Vicon cameras capture the markers on the subject moving in the capture
volume and the Start button switches to its Stop setting.
5. After you have acquired the data you need, trigger the stop of the capture from
your remote control device.
If you clicked the Lock button, the Arm button is re-enabled and the Stop button
switches to its Start again, ready for a subsequent remote capture.
6. When you have finished your capture session, to review your subject data,
manually load the trial.

Trigger data capture using timecode
The Start On Timecode and Stop On Timecode options enable you to use an external
timecode source to trigger data capture in your Vicon system. The timecode source
must be connected to a Vicon Lock+ or an MX Giganet in your Vicon system (for details,
see either the Vicon Vantage Reference Guide or Go Further with Vicon MX T-Series),
and the corresponding timecode options must be configured under the Vicon Lock or
MX Giganet node in the System Resources pane.

1.
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1. Ensure you have prepared for capture as described in steps 1–4 of Capture the
required movement on page 137.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced
properties are displayed and select one or both of the following options and
specify the required timecode:
Start On Timecode
Stop On Timecode
3. Specify the start and stop values in the standard timecode format:
hh:mm:ss:ff
where:
hh = hours (0-23)
mm = minutes (0-59)
ss = seconds (0-59)
ff = frames (0-24 for PAL/SECAM, 0-29 for NTSC)
For NTSC, the separator character changes between a colon ( : ) for non-drop
frames and a semicolon ( ; ) for drop frames.
For further details on the use of timecode functionality in Vicon systems, see
either the Vicon Vantage Reference Guide or Go Further with Vicon MX T-Series.
4. To set the system to a state where it is ready to accept a trigger signal for
automatic capture based on a timecode, click the Arm button.
5. If you want to enable the system to remain ready to receive subsequent
timecode signals after the capture is stopped, click the Lock button to the right
of the Arm button.
6. If you selected the Start On Timecode check box, start the timecode source from
which the data capture is to be triggered; otherwise, under the Capture section
click the Start button.
When the specified timecode is reached, the Vicon cameras capture the subject
moving in the capture volume and the Start button switches to its Stop setting.
7. If you selected the Stop On Timecode check box, when the specified timecode is
reached capture stops; otherwise, after you have acquired the data you need,
click the Stop button.
Nexus automatically switches to Offline mode and displays the subject data in
the 3D Perspective view.

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Trigger data capture over a network
You can broadcast a UDP message over an intranet or direct network cable connection
to or from another application (or instance of Nexus) to trigger capture start and stop.
Note that Nexus can send or receive the messages, but it cannot send and receive
them simultaneously.
To trigger data capture over a network:
1. Ensure you have prepared for capture as described in steps 1–4 of Capture the
required movement on page 137.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced
options are displayed, select Start/Stop Over Network and from the adjacent
drop-down list, select Send or Receive.
3. In the Address field, either select the IP address of the network card that will be
used to send or receive the start/stop trigger message, or select All. In the
adjacent field, specify the UDP port which is to send or receive the message.
4. To set the system to a state where it is ready to accept a trigger signal for
automatic capture based on a signal broadcast over the network, click the Arm
button.
5. If you want to enable the system to remain ready to receive subsequent network
signals after the capture is stopped, click the Lock button to the right of the Arm
button.
6. Start the capture from the remote software. You can start the capture using a
timecode or immediately.

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Automatically assess foot strikes
In clinical gait trials for kinetic analysis involving one or more force plates, Vicon Nexus
can automatically provide an indication of whether or not the foot is correctly
positioned and is producing valid data for your live trials. Nexus displays this
information on screen. This can save you time when you are assessing each foot strike
to decide whether it is valid.

As each strike is detected, or is determined to be invalid, the box representing the force
plate in the 3D Perspective view turns the appropriate color:
Red : left foot strike
Green : right foot strike
Dark gray : invalid strike
Counters on either side of the force plate box show how many valid strikes have been
detected for the left foot and the right foot during the current session.
To use auto-detection of foot strikes:
1. Before you begin, ensure that you have:
Calibrated the Vicon system.
Applied the appropriate marker set to the subject.
Ensured that you have a valid subject in Nexus.
Connected and configured one or more force plates.
2. On the Windows menu (or in the 3D Perspective view, right-click to access the
context menu), click Footstrike Monitor Settings and in the dialog box, ensure
the options for foot strikes are as required:

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2.

a. Reset footstrikes button enables you to reset the foot strike counters.
b. Force Threshold: Minimum force required on force plate to produce foot
strike
c. Marker Height Threshold: Minimum height of foot marker above force
place for foot to be recognized for foot strike
d. Left and Right Foot Markers: Comma-separated list of names of one or
more markers that define the segment (i.e. foot) that will strike the plate.

3. In the Options dialog box (press F7), ensure that Footstrikes is selected and that
the display options for Font Size, Opacity, and Background Color are as required.
To reset foot strike counters:
Right-click anywhere in the workspace and then click Reset.
or
Press CTRL+SHIFT+R

Using multiple foot plates
If your trial requires multiple force plates, they are laid out in the order of the force
plate IDs (that is, FP1 is furthest left/uppermost depending on the position of the force
plate box).
Strikes straddling two force plates are marked invalid. However, if required they can be
processed by the Process Dynamic Plug-in Gait Model pipeline operation, by selecting
the Allow cross-plate strikes option.

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Use Simple Capture Mode
Simple Capture Mode enables you to use a workspace that maximizes your view of the
capture volume and exposes a focused subset of controls required for repeated
captures, allowing you to concentrate on the movement you are capturing.
In Simple Capture Mode, only the currently selected view type is displayed, together
with controls that enable you to specify the trial type, name, and description, and to
start and stop (or cancel) captures.

To display a simplified capture view:
1. Ensure that you have set up your Vicon system as required, that Nexus is in Live
mode, and that you have set up your trial types, including any post-capture
pipeline required, auto-start triggers, etc. (For information on setting up trials,
including pipelines and triggers, see Capture the required movement on page 137
and Automatically start and stop capture on page 140.)
By default, Simple Capture Mode displays the same view as the current
workspace. You can customize the view to include other panes (eg, a video pane
alongside the 3D Perspective), as described in the following steps.
2. Associate a custom view type with Simple Capture Mode. To do this:
a. Open the Options dialog (press F7) and on the left click Simple Capture
Mode View Options.
b. On the right, from the View Type list, select On.
c. From the User Specified Simple Capture Mode View list, select one of the
following:

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c.

To use the Vicon-supplied Simple Capture view type (which displays the
view pane with a 3D Perspective view on the left, and Camera views with
video cameras selected on the right, as shown above), ensure Simple
Capture is selected; or
To use your own view type (for a reminder of the controls that enable
you to define and save a view type, see Get to know Vicon Nexus on
page 21), select the required option.
3. Turn on Simple Capture Mode. To do this:
On the Window menu, select Simple Capture Mode; or
Press CTRL+H
The simplified capture view that you selected in the Options dialog box is
displayed.
4. To capture trials, at the bottom right of the Simple Capture view, click Start.
5. To exit Simple Capture Mode, either press Esc, or press CTRL+H again. (You can
also click the Window menu and clear Simple Capture Mode.)

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Reconstruct and label movement trials
After you have calibrated a labeling skeleton for your subject (see Prepare a subject on
page 108) and captured the required movement of the subject in a trial or series of
trials (see Capture movement trials on page 136), you must reconstruct and label the
raw camera data to create 3D markers. You can do this as a separate step, as described
below, or you can specify a pipeline that includes Reconstruct and Label in the PostCapture Pipeline Setup (see Capture the required movement on page 137), so that
these operations run straight after capture.

Note
Note that you can choose to reconstruct and then label separately, or run
both operations together, by clicking either the Reconstruct button
Reconstruct and Label button

or the

on the Nexus toolbar, or by configuring and

running the equivalent pipeline operations. Normally, you would use
Reconstruct alone if you are working on a labeling skeleton template (VST),
but Reconstruct and Label if you are processing movement trials.

To reconstruct and label trial data:
1. Display the subject whose data is to be reconstructed in either of the following
ways:
If you have just captured a trial, ensure that the raw marker data for the
subject in the capture volume is still visible in a Camera view and in the
Resources pane, ensure Nexus is in Offline or Pause mode; or
On the Data Management tab, open the desired trial file containing raw trial
data for the subject.
2. Do one of the following, depending on whether you need to adjust the
reconstruct and labeling settings:
To run the operations without viewing and changing their settings, on the
Nexus toolbar, click the Reconstruct and Label button.
This runs the Reconstruct and Label operation defined in the Pipeline Tools
pane.
Or

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To view and/or change the operations, on the Pipeline Tools pane, from the
Current Pipeline list, select Reconstruct And Label. In the list of current
operations, click on Combined Processing to select it. set the Processing
Output level to the required level, for example, Labels, and specify any other
required properties.

The pipeline progress bar indicates when the operation is complete.
You can now review the results and fill any gaps in the trial data. For information, see
Review trials and fill gaps on page 152.

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Review trials and fill gaps
When you have reconstructed and labeled your movement trials (see Capture
movement trials on page 136), you can review the results and fill any gaps in the trial
data.
1. If other Nexus users may have worked on your trial data, you may first want to
check on any processing that has been performed on the files (see Review
processing history on page 153).
2. Review data quality by playing through the trial using the Time Bar and/or
looking at the information on the data Quality tab (see Review data quality on
page 154).
3. If necessary, crop any large gaps at the beginning and/or end of the trial, either
manually or automatically (see Crop trials on page 165).
4. Fill any gaps using either automatic or manual gap-filling (see Fill gaps in trial
data on page 169).
5. If required, you can add events to trials (see Add events to trials on page 180).
After you have filled any gaps in your trial data, you can run the required modeling
operations. For more information on modeling, see Modeling with Plug-in Gait on page
185.

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Review processing history
You can review all processing that has been performed on a loaded trial file on the
History tab in the Communications pane. This ensures that, even if you have not
worked with the data before, you can work on the trial without missing or duplicating
processing steps. For example, if you work as part of group, when you open a trial that
someone else has worked on, you can immediately see what processing has occurred
(eg, filtering, gap-filling) and what settings were used.
Being able to view processing history helps you to understand your data, prevents
errors introduced by running certain operations more than once (eg, filtering), and
reduces the need to reprocess data because its current state is not well known.
To view processing history:
1. Open a trial.
2. In the Communications pane, click the History tab.
A summary of the data processes and major events is displayed.
3. To display information about a particular event, click on the relevant event.
Details about the settings used to run the event are displayed in the Property
and Value columns on the right.

In the Notes field, you can add notes that will be useful to you or anyone else
working with the same trial. Your notes are saved with the trial.

Note
Processing history is available only for files processed in Nexus 2.3 and above.

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Review data quality
To enable you to review the data you captured in your movement trials (see Capture
movement trials on page 136), Vicon Nexus offers a number of tools. You can use the
time bar to manually scrub through the trial, or to assess your trials quickly and easily,
you can use the automated data quality features of Nexus.
For more information, see:
Review trial data using the time bar on page 154
Assess trial health with the data Quality pane on page 156
Detect gaps in the Graph view on page 158
View gaps with the Data Correction view on page 159
View data quality across a trial on page 161
Navigate to gaps using the data quality features on page 163

Review trial data using the time bar
To review trial data using the time bar:
1. Display reconstructed and labeled markers in either of the following ways:
Ensure that a trial you have just captured has been reconstructed and labeled.
From the Data Management tab, open a previously captured and labeled trial.
2. In the Resources pane, ensure Nexus is in Offline mode.
3. Display a 3D Perspective view and optionally a Graph view.

Tip
To automatically display both views, in the View Type list on the Nexus
toolbar, select Data Correction. Using a split layout with both a 3D
Perspective and a Graph view enables you to display the results of your
editing actions and to select specific trajectories, frame ranges, and
gaps in trajectories. Since the graphs indicate what changes have been
made to the data and by which tool, you can immediately see the results
of any edits you have made and determine if you want to change it
again or adjust the data, using a different tool in the Gap Filling section.

4.
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4. Play back the desired portion of the trial:
Full trial: In the controls at the left end of the time bar, click Play to start
playing the trial data. The data plays through to the end and restarts at the
beginning if you do not click Stop.
Range of frames: Do one of the following:
To manually adjust the range, move the blue triangles that indicate the start
and end of the selected range of frames (also known as the region of
interest) along the timeline; or
On the time bar, right-click and then click Set Region-of-Interest. In the Set
Region of Interest dialog box, specify the Start Frame and End Frame.
Individual frame: Move the blue vertical line that indicates the currently
selected time along the timeline to manually locate the desired frame, or rightclick on the time bar, click Set Current Frame and enter the number of the
required frame.

Tip
To display a context menu in which you can reset the timescale on the
timeline, set the playback speed, or specify the length of trajectory tails, click
the ellipsis (...) in the time bar controls, or right-click the time bar.

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Assess trial health with the data Quality pane
The data Quality pane, a tab in the Communications window, provides both a broad
overview of data quality for a subject across the entire trial and a way to examine the
health of individual trajectories. It also enables you to navigate to the highlighted
issues.

The three most common data issues that you need to find and resolve are:
Missing markers (usually knocked off before capture)
Unlabeled or incompletely labeled trajectories
Gaps in trajectories
The Quality tab helps you to find this information:

Overview of the health of the whole trial (Labeling column) The text in each
rectangle indicates the number of unused markers, any gaps, and the
percentage of markers labeled. As a quick indicator, to enable you to assess
whether to continue working with the trial, the color green indicates good
health, red indicates probable major issues, and colors between the two
(yellow, amber, orange) indicates that the overall health of the trial lies
somewhere between these extremes.

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For example, a good trial, worth further
work, would be indicated by:
No missing markers
A high percentage of labeled markers
Only a small number of gaps.
A low quality trial, which would probably
have to be re-run, would be indicated by:
Missing markers, and/or
A high number of gaps, and/or
A lower percentage of labeled markers.
In this example, two required markers are
completely absent from the trial, so, without
further work, you would know that you
would have to either re-reconstruct or (more
likely) re-capture the trial.

Individual trajectories. If you hover the mouse over a blob, the blob displays
information about the trajectory. If you click on it to select it, information
about the trajectory is displayed in the Selection column on the right. For more
information, see Navigate to gaps using the data quality features on page 163.
General trial information/selected trajectory Information (Selection column). If
no blob is selected, general information about the currently loaded trial is
displayed. If a blob is selected, information about the trajectory is displayed.
Display options (Options column): Enables you to configure the display options
for the data Quality tab. Alternatively, you can open the Options dialog box
(F7), click Data Quality Panel Options on the left, and change the properties as
required. To save any changes to these settings, click the Save current
configuration button in the Options dialog box.

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Detect gaps in the Graph view
The Graph view enables you to view and fix gaps for a selected trajectory.

To display gaps:
1. On the Quality pane, click a trajectory blob that is reporting a gap.

Gap indicators are displayed in pink in the Graph view.

2. To zoom in and out, CTRL+double-click on a gap indicator (the pink area) on the
graph.

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View gaps with the Data Correction view
The default Data Correction view type displays a 3D Perspective view above a Graph
view.

You can turn Data Correction view on or off in the Options dialog box, as described
below.
When the Data Correction view is turned on, it is automatically displayed when you
navigate using the data Quality pane.
If you would prefer the Data Correction view to appear differently (for example,
displaying the Graph above the 3D Perspective view), you can save your own preferred
view and select this instead.

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To configure the Data Correction view:
1. Open the Options dialog box (F7).
2. Click on Data Correction View Options on the left and change the properties as
required on the right:
a. If you want to display this view type automatically when you are
navigating via the Quality tab, ensure View Type is set to On.
b. If you have saved a different view type to be displayed when you are using
the Quality tab, ensure it is selected in the User Specified Data Correction
View field.

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View data quality across a trial
In addition to viewing data quality on the Quality tab and Graph and Data Correction
views, you can also view data quality as a heat map on the time bar, to get an overall
picture of the current trial.

To turn on the heat map overlay:
1. In the Options dialog box (F7), click on Time Bar on the left, and select the Heat
Map Visible check box on the right.
2. If required, change the colors of the heat map.

When you click on a trajectory on the Quality tab, the time bar shows gaps for the
selected trajectory.

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Viewing data quality for multiple trajectories
To select multiple trajectories, on the Quality tab, CTRL+click the required blobs.
When multiple trajectories are selected, the heat map's color gradient system is
activated.
Lighter colors show where one of the trajectories has a gap but other selected
trajectories do not. Darker areas show where a number of selected trajectories has a
gap.

Two trajectories selected
The following images show two trajectories selected. The darker area indicates gaps in
both trajectories.

More trajectories selected
As more trajectories are added the view starts to morph from individuals gaps for one
or two trajectories, to areas in the volume/time where there are issues.

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Navigate to gaps using the data quality features
Using the Quality tab and the Data Correction view type, you can quickly navigate to
gaps in data, and use the Zoom, Translate, and Rotate options for a better view.

Quick navigation to gaps
To quickly navigate to gaps:
1. On the Quality tab, click on a trajectory blob.
Immediately, the time bar and view pane displays the first gap (if any) for the
selected trajectory.

2. To move to the next gap or previous gap for the selected trajectory, press the hot
keys CTRL+8 and CTRL+7 respectively.

Tip
On the data Quality tab, you can move to the next trajectory and
previous trajectory by pressing CTRL+PgUp and CTRL+PgDown.

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Get a better view of gaps
The Zoom, Translate and Rotate options for viewing a gap make it easier to zoom in on
and fix selected gaps.
To view gaps more clearly:
1. In the Options dialog box (F7), click General View Options on the left.
2. In the Properties pane on the right, in the 3D View Options section, click the
Focus on Selection Mode list.
3. To display a zoomed view that rotates the workspace to a flat perspective of the
gap, click Zoom, Translate and Rotate.

4. On the Quality tab, click the blob for the trajectory whose gaps you want to
examine.
The 3D Perspective view zooms in and rotates as necessary to clearly show the
selected trajectory's first gap.

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Crop trials
For trials where the subject starts outside the volume, moves into the volume and then
exits, cropping the start and end of the trial removes unwanted frames where the
subject was not fully in the volume.
Before you fill gaps in your trial data, it's a good idea to remove these start and end
frames as they are likely to contain large gaps and other invalid data. You can do this
automatically while capturing (see Trigger data capture on labeling percentage on
page 141), or for trials that have already been saved, you can crop trials manually or run
a pipeline operation to do this automatically.
Cropping a trial affects only the .c3d file. The raw files remain unchanged.

Tip
If you add gait cycle events and then crop a trial, you will probably also want to
delete events that are outside the cropped region. For information on how to
do this, see Delete events that are outside the region of interest on page 183 .

For more information, see:
Manually crop a trial on page 166
Automatically crop a trial on page 167

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Manually crop a trial
You can use tools on the time bar to remove unwanted frames at the start and end of
your trials.
To manually crop a trial:
1. Ensure the required trial is reconstructed and labeled (see Reconstruct and label
movement trials on page 150).
2. On the time bar, do one of the following:
Move the range indicators (blue triangles) to exclude the unwanted frames at
the beginning and/or end of the trial; or
Right-click and then click Set Region-of-Interest. In the Set Region of Interest
dialog box, specify the Start Frame and End Frame.
The gray shaded area represents the cropped frames of the trial.
3. Right-click on the time bar and click Zoom to Region-of-Interest.
You can now fill any remaining gaps.

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Automatically crop a trial
Nexus can save you time and effort by automatically determining the first and last
frame where the subject is fully in the volume
When you run the autocrop operation, Nexus automatically zooms the time region of
interest to the points where the subject first fully enters and then leaves the volume.
To set up auto-cropping:
1. Ensure the required trial is reconstructed and labeled (see Reconstruct and label
movement trials on page 150).
2. In the Tools pane, click the Pipelines tab and in the Available Operations list,
expand Events & Timebar.
3. Double-click the Auto Crop Trial pipeline operation to add it to the current
pipeline.

4. In the Current Pipeline list, click Auto Crop Trial and in the Properties pane,
ensure that the First and Last Frame options are set to the beginning and end
frames during which the subject enters and leaves the volume.

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5. Set the Start and End (%) options to the required minimum percentage of
markers (ie, the percentage of markers expected from the total number of
markers in your subject's labeling skeleton) that must be labeled in each case.

6. If necessary, adjust the Frames Required to set a minimum number of frames
where the Start % criterion must be met. This is helpful if early single frames of
data meet the %, but the point at which the trial is intended to start (ie, the point
at which the % is maintained over a number of frames) is later in the trial.
7. Run the Auto Crop Trial operation.
The trial is automatically cropped to the frames you have selected.
You can now fill any remaining gaps.

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Fill gaps in trial data
When Nexus reconstructs each marker on a subject, ideally it produces a smooth
trajectory throughout the trial. Realistically, there may be frames with breaks in
trajectories due to some markers that could not be reconstructed or spurious data.

Tip
Auto Gap Fill attempts to fill all gaps in the trial data. For this operation to
work well, you are likely to need to change the default property settings,
including the gap size. For data containing large gaps, you are advised to
review and manually fill the large gaps first, using the tools in the Label/Edit
Tools pane, and/or cropping out any unwanted frames with large gaps that
occur at the start or end of the trial.
For information on cropping frames at the start and end of the trial data, see
Crop trials on page 165.

For more information, see:
Manually fill gaps in trial data on page 170
Automatically fill gaps in trial data on page 177
Example of creating a custom pipeline for gap-filling on page 179
In addition, a Vicon Nexus 2 tutorial video, showing gap-filling operations, including
many additional tips and examples, is available on YouTube.

Note
As the videos were recorded using an earlier version of Nexus 2, you may
notice small differences in the user interface.

For additional tips on issues you may encounter when using manual labeling, see
Improve manual labeling in the Vicon Nexus Reference Guide.

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Manually fill gaps in trial data
You can manually fill any gaps in the reconstructed and labeled trial data by using the
tools in the Label/Edit Tools pane.
As well as automatically filling gaps (see Automatically fill gaps in trials on page 177),
you can manually fill gaps to correct any errors or inconsistencies in the reconstructed
and labeled trial data.
To manually fill gaps in reconstructed and labeled data:
1. Display reconstructed and labeled markers, ensure Nexus is in Offline mode, and
display a 3D Perspective view and optionally a Graph view, as described in
Review trial data using the time bar on page 154.
2. Unless you have already cropped your trial (see Crop trials on page 165), to
simplify cleaning up your data, set the region of interest of the trial that you wish
to analyze. For example, if the capture includes the subject entering and leaving
the capture volume, Vicon recommends that you set the range of frames to
exclude these parts of the capture, as they are likely to include large gaps. To do
this, on the time bar, move the blue range indicator triangles to select a range of
frames and then right-click and click Zoom to Region-of-Interest.
3. In the Subjects tree, ensure that the desired subject is selected (when selected,
there is a check mark in the check box).
In the Label/Edit tools pane, in the Gap Filling section, any markers whose
trajectories contain gaps within the selected range of frames are listed in the
Trajectory column, with the number of gaps for each trajectory identified in the
#Gaps column and the largest gap length in the Max Gap Length column.

Tip
To jump to the largest gap for a particular trajectory, double-click in its
Max Gap Length column. To change the sort order of the columns, click
the column headings.

4. In the Trajectory column, click on the trajectory whose gaps you want to fill.
Nexus automatically selects the gap by placing the current time in the middle of
the gap and positioning the gap range selectors (blue cones) at the start and end
of the gap. A red dotted line is displayed to preview the shape of the trajectory if
a spline fill editing operation is run. If you can't see a red dotted line, in the Label
/Edit Tools pane, in the Gap Filling section, hover the mouse pointer over the Fill
button in the Spline Fill area to display a tooltip.

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5. In the Range section, view the range values to identify the size of the gap and
use the buttons to navigate between the gaps in the selected trajectory:
Prev Gap: Navigate to the previous gap in the selected trajectory. This button
is available only if there are gaps in the trajectory before this point.
Left edit range: The frame before the start gap range selector, indicating the
start of the gap that will be filled in.
Right edit range: The frame after the end gap range selector, indicating the
end of the gap that will be filled in.
Next Gap: Navigate to the next gap in the selected trajectory. This button is
available only if there are gaps in the trajectory after this point.
6. If required (for example, if the data leading up to the gap is noisy), to extend the
edit range beyond the gap, in the 3D Perspective view, drag the gap range
selectors (blue cones).

If you need to adjust the size of the cones for easier viewing or
selection, open the Options dialog box (press F7) and click Trajectory
Editor. Adjust the value of Radius as required (the default is 10 pixels).

7. Use the appropriate fill tool to generate data to fill the selected gap.

Tip
If your chosen tool is unavailable, hover the mouse pointer over the
unavailable button to display a tooltip that explains how to use it.

The fill options are:

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Spline Fill: Performs a cubic spline interpolation operation to fill the currently
selected gaps. Use it when you have suitable frames with no gaps on either
side of the gap. If there are gaps in these frames, the fill is rejected and you will
need to choose a different gap-filling method. For more information, see Fill
gaps with Spline Fill on page 173.
Pattern Fill: Uses the shape of another trajectory without a gap to fill the
selected gap. Use this tool only if there is a suitable marker with a trajectory
similar to the one whose gap you wish to fill. This is typically the case when the
trajectories originated from markers attached to the same segment, such as
those attached to the ankle or heel. For more information, see Fill gaps with
Pattern Fill on page 174.
Rigid Body Fill: This option is the Nexus equivalent of the Replace 4 option,
which is available in BodyBuilder. Use this option when a rigid or semi-rigid
relationship exists between markers. For more information, see Fill gaps with
Rigid Body Fill on page 175.
Kinematic Fill: This option uses information about the connection of markers
to segments in the labeling skeleton template (VST). For this option to be
available, you may first need to run the Kinematic Fit pipeline operation, by
clicking the KinFit button on the Nexus toolbar.For more information, see Fill
gaps with Kinematic Fill on page 176.
Cyclic Fill: For trials that contain captured data that is cyclic in nature (for
example, when a motion on a treadmill or other repetitive motion is captured),
this option uses patterns from a missing marker from earlier or later gait cycles
to fill gaps. (If you want to modify the supplied operations, you can change and
run the Fill Gaps - Cyclic pipeline operation instead.) For more information, see
Fill gaps with Cyclic Fill on page 176.

Tip
For data with smaller gaps, you could use a processing pipeline
containing the Fill gaps (Woltring) operation to automatically fill gaps.

8. In the chosen gap fill area, click the appropriate option:
To have Nexus fill the selected gap, click Fill.
To have Nexus fill all the gaps in the selected trajectory with the currently
chosen type of gap filling, click All. This feature is particularly useful when, for
example, you have 7 gaps in LASI and you want to fill them all with a Rigid Fill
from the other pelvic markers (RASI, RPSI, LPSI).

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For Pattern Fill or Rigid Body Fill, you can click Auto before clicking Fill or All.
When a gap is filled, Nexus reduces the entry in the #Gaps column by one and
selects the next gap.
When all gaps for the selected trajectory have been successfully filled, the entry
for the trajectory is automatically removed from the Trajectory list and Nexus
selects the next trajectory.
9. Repeat steps 4–8to fill all the gaps for all trajectories.
10. On the Nexus toolbar, click the Save button to save the trial. You can then
perform any other processing that is required, such as running pipelines.

Tip
To save time, you can create custom pipelines that include the type of gapfilling operations that you commonly perform, such as Rigid fills for Pelvis and
Head markers. For more information, see Example of creating a custom
pipeline for gap-filling on page 179.

Use the gap filling options
The following information provides instructions on how to use the Vicon Nexus gapfilling options. (For detailed information about the Nexus gap-filling algorithms, see the
FAQ What Gap Filling Algorithms are used in Nexus 2? on the Vicon website.)

Fill gaps with Spline Fill
1. Ensure the required gap is selected (see Manually fill gaps in trial data on page
170).
2. Under Spline Fill, in the Maximum gap length field, specify the maximum number
of frames to spline fill (the default is 100 frames).
3. Click the appropriate button:
To have Nexus fill the selected gap, click Fill.
To have Nexus spline fill all the gaps in the selected trajectory, click All.
A cubic spline interpolation operation fills the specified gaps.

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Fill gaps with Pattern Fill
1. Ensure the required gap is selected (see Manually fill gaps in trial data on page
170).
2. Under Pattern Fill, click Pick Source or Auto:
If you click Pick Source:
a. The shape of the pointer changes to include a tooltip to guide you in the
selection of markers in the 3D Perspective view. Initially, a tooltip with the
text Pick source marker hangs from the cursor.
b. In the 3D Perspective view, click a source marker whose trajectory is to be
used to fill the gap of the target marker.
A green dotted line is displayed to preview the shape of the trajectory if a
pattern fill editing operation is run with the selected source model.
Nexus displays the name of the source marker at the bottom of the
Pattern Fill section, so you can confirm that you have selected the desired
trajectory.
c. In the Pattern Fill section, click Fill to have Nexus fill the selected gap (or
All to fill all gaps in the selected trajectory), with the shape of the filled-in
trajectory being similar to the trajectory of the source marker.
If you click Auto:
a. A suggested donor trajectory is listed in the space above the Auto button
and the suggested fill is displayed in green in the 3D Perspective window.
You can also view the suggested fill options as colored dotted lines in the
Graph view.
b. Do one of the following:
To accept the suggested donor, click Fill or All; or
To reject the suggestion and manually pick a source, click the Clear
selected donor button

, click Pick Source, then click (or CTRL+click

to multi select), the required trajectory, and then click Fill or All.

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Fill gaps with Rigid Body Fill
This option is the Nexus equivalent of the Replace 4 option, which is available in
BodyBuilder.
Use it when a rigid or semi-rigid relationship exists between markers. For example:
Pelvis (LASI, RASI, LPSI, RPSI)
Head (LFHD, RFHD, LBHD, RBHD)
1. Ensure the required gap is selected (see Manually fill gaps in trial data on page
170).
2. In the Rigid Body Fill area, click Pick Source or Auto.
If you click Pick Source:
a. Click (or CTRL+click to multi select), the required trajectory
b. Click Fill or All.
If you click Auto:
a. Three trajectories are listed in the space above the Auto button and the
suggested fill is displayed in green in the 3D Perspective window. You can
also view the suggested fill options as colored dotted lines in the Graph
view.
b. Do one of the following:
To accept the suggested donor, click Fill or All; or
To reject the suggestion and manually pick a source, click the Clear
selected donor button

, click Pick Source, then click (or CTRL+click

to multi select), the required trajectory, and then click Fill or All.

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Fill gaps with Kinematic Fill
This option uses information about the connection of markers to segments in the
labeling skeleton (VSK).
1. To provide the required kinematic data, ensure you have clicked the KinFit
button or run a pipeline operation that includes kinematic fitting.
2. Ensure the required gap is selected (see Manually fill gaps in trial data on page
170).
3. In the Kinematic Fill area, click Pick Segment and in the 3D Perspective view
select the segment from which the kinematics will be copied.
The suggested fill is displayed in purple in the 3D Perspective view. You can also
view the suggested fill options as colored dotted lines in the Graph view.
4. Do one of the following:
To accept the suggested donor, click Fill or All; or
To reject the suggestion and try again, click the Clear selected donor button
, click Pick Segment, then click (or CTRL+click to multi select), the required
trajectory, and then click Fill or All.

Fill gaps with Cyclic Fill
1. Ensure you have captured a trial containing repetitive motion.
2. Select the gap/range that is to be filled (see Manually fill gaps in trial data on
page 170).
3. In the 3D Perspective view and the Graph of the marker component, preview the
gap fill solution provided by Nexus.
4. If the suggested solution is acceptable, in the Label/Edit Tools pane, ensure Gap
Filling is expanded.
5. In the Cyclic Fill area, select the required option:
Fill Fills the currently selected range
All Attempts to fill all gaps in the selected trajectory.
The gap is filled with data based on other cycles of the same movement.

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Automatically fill gaps in trial data
You can automatically fill gaps using the Auto Gap Fill button on the Nexus toolbar or
the equivalent Auto-Intelligent Gap Fill pipeline in the Pipeline tools pane. This enables
you to quickly fill gaps in your trial, without having to choose which fill method is best
for each gap. You can do this in a one-click operation or, if you want to modify the
supplied operations, by changing and running the Auto Intelligent Gap Fill pipeline.

Tip
Auto Gap Fill attempts to fill all gaps in the trial data. For this operation to
work well, you are likely to need to change the default property settings,
including the gap size. For data containing large gaps, you are advised to
review and manually fill the large gaps first, using the tools in the Label/Edit
Tools pane (see Manually fill gaps in trial data on page 170), and/or cropping
out any unwanted frames with large gaps that occur at the start or end of the
trial. For information on cropping frames at the start and end of the trial data,
see Crop trials on page 165.

To automatically fill gaps in trial data:
1. Display reconstructed and labeled markers in either of the following ways:
Ensure that a trial you have just captured has been reconstructed and labeled;
or
From the Data Management tab, open a previously captured, reconstructed
and labeled trial.
2. In the Resources pane, ensure Nexus is in Offline mode.
3. Display a 3D Perspective view and optionally a Graph view.

Tip
Using a split layout with both a 3D Perspective and a Graph enables you
to view the results of your editing actions and to select specific
trajectories, frame ranges, and gaps in trajectories. Since the graphs
indicate what changes have been made to the data and by which tool,
you can immediately see the results of any edits you have made and
determine if you want to change it again or adjust the data using one of
the tools in the Label/Edit Tools pane.

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4. In the Nexus tool bar, click Auto Gap Fill.

Nexus assesses each gap one-by-one in series and fills all the gaps.
To use the Auto Intelligent Gap Fill pipeline:
1. On the Tools pane, click the Pipelines button.
2. From the Current Pipeline list, select the Auto Intelligent Gap Fill pipeline.

3. From the list of operations below, select the gap-filling operations that you want
to use. If required, in the Properties pane, modify the relevant settings to suit
your particular trial.
For more information on an operation, either view its tooltip by clicking on its
name and then hovering the mouse pointer over it or see the FAQ What gapfilling algorithms are used in Nexus 2? on the Vicon website.
4. Either click the Run button or use the Auto Gap Fill button on the tool bar, as
described above, to run the pipeline with any changes you have made.
5. On the Nexus toolbar, click the Save button to save the trial. This will enable you
to load the edited trial data. You can then perform any other processing, such as
manually filling any remaining gaps.
You can run the pipeline either on an individual trial in the Pipeline Tools pane or on
multiple files using the Batch Processing Interface.

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Example of creating a custom pipeline for gap-filling
The following steps describe how to make a custom pipeline for speeding up gap-filling
operations. (For a reminder of how to create and run pipelines, see Work with pipelines
on page 131.)
To create a custom gap-filling pipeline:
1. Create a new pipeline (for example, called Head and Pelvis Fill), which contains
two Rigid Body fill operations.

2. Click on each operation in turn and in the Properties pane, customize the fills so
that Pelvis and Head markers will be filled appropriately. For example:
Pelvis Rigid Fill properties

Head Rigid Fill properties

3. Save the pipeline.
4. Add a new button to the Nexus toolbar (Window menu > Toolbar) to give quick
access to your custom pipeline.

Now, with one mouse click, you can automatically fill any Pelvis and Head gaps.

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Add events to trials
An event is a single action in the time span of a trial, for example, a foot contacting the
floor during a walking trial, or a knee angle exceeding a particular angle.
Events are normally added to your trial data automatically as part of the capture
workflow, when you run Plug-in Gait Dynamic or other dynamic pipelines that include
Detect Events From Forceplate and Autocorrelate Events. For more information, see
step 7 of Capture the required movement on page 137.
However, if events are not automatically detected, or are only partially detected, you
will need to add them manually. This is likely to be necessary in the following scenarios:
If you are not using a force plate; or
The floor is not flat (ie, the movement being captured involves stepping, climbing,
etc); or
The trial includes movement that is not a cyclical gait movement (for example, some
sports movements)
If your trial type does not allow the automatic addition of events, you can add them
manually, using the timebar as described below.
For more information on working with events, see:
Add events to trial data on page 180
Delete events that are outside the region of interest on page 183
Customize event identification mode on page 183
Customize cycle visualization on page 183

Add events to trial data
To add events to motion capture trial data:
1. From the Data Management tab, open the required trial, ensuring that it contains
no gaps or other issues (see Review data quality on page 154 and Fill gaps in
trial data on page 169).
2. Display the desired view (3D Perspective, 3D Orthogonal, Camera, or Graph).
3. Enter event identification mode in either of the following ways:
On the time bar, click the Enter Event Identification Mode button; or.

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Press CTRL+E.
The mouse pointer changes to a vertical arrow, to indicate that you are now in
event identification mode.
4. On the time bar, zoom in or out on the timescale (right-click and drag) to adjust
the time span of data displayed in the view pane and move the current time
indicator (blue line) along the time bar to locate the desired frame.
5. Lock the event context by positioning the mouse pointer over the desired Left,
Right, or General line on the selected frame (the line for a context is highlighted
when the mouse pointer hovers over it) and pressing the UP ARROW or DOWN
ARROW key. When the event context is locked, moving the mouse does not
change the context.
6. Set a new event in the current context on the selected frame by either leftclicking or pressing ENTER and then selecting the desired command from the
context menu
Create Event Foot Strike Creates a foot strike event at the selected frame.
Create Event Foot Off Creates a foot strike event at the selected frame.
Create Event General Creates a general event at the selected frame,
represented by a vertical bar on the timeline. You cannot name general events
and they are not saved to the event creation menu for future use.
Create Custom Event Creates a custom event at the selected frame that you
can name, represented by a caret ( ^ ) on the timeline. When you create and
name a custom event, it is added to the event creation menu, so you can select
it again in future.

7. Navigate existing events in either of the following ways:
In the time bar controls, click the Jump to the previous event or Jump to the
next event button; or
Press CTRL+LEFT ARROW or CTRL+RIGHT ARROW to go the previous or next
event.

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8. If required, you can:
Move an existing event to another frame by clicking in it with the left mouse
button, holding the button down, dragging it left or right along the timeline.
Move the event at the current frame in the current context back or forward
one frame by pressing ALT+Left- or Right-arrow key.
Delete existing events:
Single event: On the time bar, click the event or press ENTER, and from the
displayed context menu select Delete Event .
All events on current frame: On the time bar, click the desired event or press
ENTER, and from the displayed context menu select Delete All Events at
Frame x.
All events in trial: On the time bar, right-click anywhere and from the
displayed context menu select Clear All Events.

Tip
Note that you can also use the Delete Timebar Events pipeline
operation (available on the Pipeline Tools pane, under Events &
Timebar) to delete events from a selected range of frames.

9. When you have finished editing the current event context, unlock the event
context by either moving the mouse over a different context or using the Up
/Down arrow keys on the keyboard.
10. Repeat steps 5-9 for each event context you wish to edit.
11. When you have finished editing all events, exit event identification mode in any
of the following ways:
In the timebar controls, click the Enter Event identification mode button again;
or
Press CTRL+E; or
Press ESC
If you add gait cycle events before you crop a trial, you probably want to delete events
that are outside the cropped region. (For information on cropping trial data, see Crop
trials on page 165.)

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Delete events that are outside the region of interest
If you crop a trial after you have added events to it, events may be retained in the
discarded (cropped) region of the trial. To remove these events, do either of the
following:
To delete events that are outside the region of interest:
1. Do either of the following:
Right-click on the time bar of the cropped trial and click Delete Events Outside
Region of Interest; or
In the Pipeline Tools pane, from the Events & Timebar operations, select Delete
Timebar Events and in the Advanced Properties, select whether to delete
events inside or outside of the specified region.
2. Run the Delete Timebar Events operation to remove the unwanted events.

Customize event identification mode
To customize options that affect event identification mode:
1. Open the Options dialog box (press F7).
2. On the left of the dialog box, click Time Bar.
3. In the Event Identification Mode section on the right, select (or clear) Focus on
marker and enter or select the markers to focus on for Left and Right contexts.

Customize cycle visualization
By default, all the cycles (gait or other) that have been defined by sets of time bar
events, are displayed on the time bar.

This provides an easy way to identify:
How many cycles are defined
Where they are temporally
Whether they are associated with force plate activity (indicated by solid color instead
of colored outline only)
How large they are (number of frames)

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Whether the left or right side is indicated:
Left = Red
Right = Green
To turn the visual display on or off or to change the default color options and other
visual indicators, in the Options dialog box (press F7), on the left side click Time Bar and
change the required properties on the right.
To turn on or off the display of the frame count, right-click on the time bar and select or
clear Show Cycle Frame Count.

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Modeling with Plug-in Gait
Vicon Nexus provides you with the following options for modeling:
Plug-in Gait and the Oxford Foot Model. If you are new to modeling with Nexus, the
Plug-in Gait model provides a good introduction: all the operations necessary to run
the model are supplied with Nexus, easily accessible and ready to use. This option is
described in this guide. For further details, see:
About the Plug-in Gait model on page 187
Plug-in Gait files installed with Vicon Nexus on page 189
How Plug-in Gait works on page 190
Take subject measurements for Plug-in Gait on page 191
Attach Plug-in Gait markers to a patient on page 199
Plug-in Gait Static pipeline on page 201
Plug-in Gait Dynamic pipeline on page 203
In addition, a Vicon Nexus 2 tutorial video, PlugIn Gait AI: Marker Locations and

Subject Measurements, is available on YouTube.

Note
As the videos were recorded using an earlier version of Nexus 2, you may
notice small differences in the user interface.

MATLAB. If you are familiar with MATLAB, you can use the supplied examples to
create your own custom models. For more information, see Modeling with MATLAB ,
in the Vicon Nexus Reference Guide.
Python. If you are familiar with Python, you can use the supplied examples to create
your own custom models. For more information, see Modeling with Python , in the

Vicon Nexus Reference Guide.

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Note
For simplicity, modeling operations are described as separate steps. However,
if you want to run modeling operations automatically, you can add them (and
any other operations required) to a post-capture pipeline that runs as soon as
capture finishes. For more information see step 7 in Capture the required
movement on page 137.

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About the Plug-in Gait model
The Plug-in Gait model is Vicon's implementation of the Conventional Gait Model,
which provides widely used and reliable full body kinematic and kinetic modeling,
without the need for any customizations. It is based on the Newington-Helen Hayes
gait model and has been validated through its frequent citation in peer-reviewed
publications (see Plug-in Gait references on page 188).
Vicon Nexus includes the required pre-defined Plug-in Gait marker set and pipelines to
enable you to produce outputs of the joint kinematics and kinetics for gait analysis
patients. Plug-in Gait enables you to examine full, upper, or lower body joint kinematics
and kinetics of patients. When you have run the relevant pipeline operations on your
trials, you can produce gait analysis reports that conform to established clinical
practices and import the resulting kinematic model of your subject (patient) into
another software application, such as Vicon Polygon, for gait analysis.
It is assumed that you are familiar with Plug-in Gait, including the way the model works,
where the markers are placed, and what the subject parameters mean. For example,
Plug-in Gait directly calculates the kinematic model's joint centers from the measured
XYZ marker positions on a frame-by-frame basis. Therefore, the lengths and
orientations of the modeled segments are directly dependent on the marker positions.
Accurate marker placement is therefore paramount. For guidance on marker
placement, see Attach Plug-in Gait markers to a patient on page 199.
The model uses three or more points to define each segment. For all segments distal to
the pelvis, one of the points used is the joint center that defines the proximal joint for
the segment, for example, one of the three defining points for the tibia is the knee joint
center.
Operations relating to modeling with Plug-in Gait are available in the Data Processing
operations in the Pipeline Tools pane.
For in-depth descriptions of Plug-in Gait models and templates, and details of the
calculations performed by Plug-in Gait, see the Plug-in Gait Reference Guide.
Before using Plug-in Gait, be sure to read the Plug-in Gait disclaimer on page 188.

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Plug-in Gait references
The following research publications provide supporting information on the scientific
basis and validation of Plug-in Gait:
DAVIS R., OUNPUU S., TYBURSKI D., and GAGE J. R. A gait analysis collection and

reduction technique . Human Movement Science, 10, p575–587, (1991).
KADABA M. P., RAMAKRISHNAN H. K., and WOOTTEN M. E. Measurement of lower

extremity kinematics during level walking. Journal of Orthopaedic Research, 8, p383–
392, (1990).
WOLTRING, H. J. A FORTRAN package for generalized, cross-validatory spline

smoothing and differentiation, Advances in Engineering Software, 8, p104–113,
(1986).
VAN DEN BOGERT, T. Practical Guide to Data Smoothing and Filtering. See
http://isbweb.org/software/sigproc/bogert/filter.pdf

Plug-in Gait disclaimer
You are entirely responsible for the use you make of the software. In particular, the
software is not intended to replace the clinical skill of a medical practitioner or his/her
independent professional judgment of individual clinical circumstances to make a
diagnosis and/or determine a patient's treatment.
The software should only be used by those who have been appropriately trained in its
operation, functions, capabilities, and limitations, and in any event should not be relied
upon, by itself, as the sole method of making any diagnosis or determining any
treatment.

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Plug-in Gait files installed with Vicon Nexus
The following table lists the Plug-in Gait files that are automatically installed with
Nexus. For more detailed information about the labeling skeleton template (. vst) files,
see the Plug-in Gait Reference Guide.
File name

Description

PlugInGait FullBody Ai.vst

Full body labeling skeleton template

PlugInGait LowerBody Ai.vst

Lower body labeling skeleton template

Marker set

PlugInGait FullBody Ai.mkr

Markers defined in full body model

PlugInGait LowerBody Ai.mkr

Markers defined in lower body model

By default, the supplied files are installed in the following folder:

C:\Program Files (x86)\Vicon\Nexus2.#\ModelTemplates

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How Plug-in Gait works
To work with Plug-in Gait, you enter subject-specific measurements into a pre-defined
template in Vicon Nexus, place a Plug-in Gait marker set on a patient, capture the
required trials, and then use Plug-in Gait pipelines in Nexus to produce outputs of the
joint kinematics and kinetics for the patient.
From the real marker trajectories, Plug-in Gait generates virtual marker trajectories that
represent kinematic and kinetic quantities (angles, moments, etc) and representations
of the modeled segments. The model also outputs data that is used to define the
positions of meshes (representing bones) which can subsequently be displayed in
Vicon Polygon (for further details, see the Vicon Polygon documentation).

For detailed information about modeling with Plug-in Gait, see Plug-in Gait kinematic

and kinetic calculations in the Plug-in Gait Reference Guide.
Before you begin capturing, make sure you understand the types of outputs that Plugin Gait produces, so that you can determine the appropriate model to use for your
requirements. If you are unsure which is the most appropriate model to use, see Models

and templates in the Plug-in Gait Reference Guide.

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Take subject measurements for Plug-in Gait
Plug-in Gait requires a set of subject measurements to enable it to directly calculate
kinematics (angles) and kinetics (forces, moments, and powers) from the measured XYZ
marker positions. Some of the measurements you must add to the subject node are
required for the model to run, and some are optional:
Required subject measurements You must add the required measurements to the
subject node for your patient. Required measurements are listed in the following
topics and are highlighted in pink in the Properties pane for the selected subject in
Vicon Nexus.
Optional measurements You can add any optional measurements or leave them for
Plug-in Gait to calculate.
The following topics list the measurements needed for each type of model:
Subject measurements for Plug-in Gait lower body model on page 192
Subject measurements for Plug-in Gait full body model on page 195

Tip
You may find it helpful to take these measurements before you begin the
subject preparation process in Vicon Nexus. You can use the Measure column
in the tables in these sections to record the measurements you take for your
patient, so you will have them to hand when you are ready to add them to your
chosen labeling skeleton template (.vst file). You may want to photocopy the
blank form for each patient before recording your measurements.To avoid the
markers getting in the way, take the measurements before attaching markers
to your patient.

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Subject measurements for Plug-in Gait lower body model
The following table identifies the subject measurements that are used as inputs for
running a Plug-in Gait lower body model.
Optional measurements (and/or those calculated by the model) are marked with an
asterisk in the Name column.
Name

Description

Measure

Left

Right

Body Mass

Patient mass.

_____ kg

Height

Patient height.

_____
mm

*Inter ASIS

The model calculates this distance based

_____

distance

on the position of the LASI and RASI

markers. If you are collecting data on an
obese patient and cannot properly place
the ASIS markers, place those markers
laterally and preserve the vector direction
and level of the ASIS. Palpate the LASI and
RASI points and manually measure this
distance, then input into the appropriate
field.
Leg Length

Full leg length, measured between the ASIS

_____

marker and the medial malleolus, via the

knee joint. Measure with patient standing,
if possible. If the patient is in the crouch
position, this measurement is NOT the
shortest distance between the ASIS and
medial malleoli, but rather the measure of
the skeletal leg length, so if a patient
cannot straighten his/her legs, take the
measurement in two pieces: ASIS to knee
and knee to medial malleolus.

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Name

Description

Measure

Left

Right

*ASIS-

ASIS-greater trochanter distance is the

_____

Trochanter

vertical distance, in the sagittal plane,

Distance

between the ASIS and greater trochanter

The medio-lateral width of the knee across

_____

the line of the knee axis. Measure with

The medio-lateral distance across the

_____

malleoli. Measure with patient standing, if

when the patient is lying supine. Measure
this distance with the femur rotated such
that the greater trochanter is positioned as
lateral as possible.
Knee Width

patient standing, if possible.
Ankle Width

possible.
*Tibial Torsion

The angle between the knee flexion and

_____

the ankle dorsi-plantar axes. The ankle is

deg

usually externally rotated with respect to
the knee flexion axis.
If you are using a KAD, and the medial
malleoli markers are attached to the
patient, Plug-in Gait calculates the tibial
torsion automatically.
*Sole

The difference in the thickness of the sole

_____

Thickness

at the toe and the heel. A positive sole delta

Delta2

indicates that the patient's heel is raised
compared with the toe.

*Thigh

When a KAD is used, this value is calculated

_____

Rotation

to account for the position of the thigh

deg

marker. By using the KAD, placement of the
thigh marker in the plane of the hip joint
center and the knee joint center is not
crucial. If you do not use a KAD, this value is
zero as the model assumes that the thigh

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Name

Description

Measure

Left

Right

marker is placed exactly in the plane of the
hip joint center and the knee joint center.
This value is calculated for you.
*Shank

Similar to the Thigh Rotation. This value is

_____

Rotation

calculated if a KAD is present and removes

deg

the importance of placing the shank marker
in the exact plane of the knee joint center
and ankle joint center. If you do not use a
KAD, this value is zero. It is calculated for
you.
1. The tibial torsion measurement is only needed if you are using a KAD.
2. The Sole Thickness Delta subject measurement is used if the subject is wearing
high-heeled footwear but can keep their foot flat within the shoe. For more
information, see Sole Thickness Delta subject measurement on page 194.
After you have recorded the measurements for your patient, you can create a subject
node for the patient and enter the measurements into Nexus as described in Create a
new subject from a template on page 110.

Sole Thickness Delta subject measurement
The Sole Thickness Delta subject measurement is used when the patient is wearing
shoes or orthoses so that although the patient achieves foot flat with respect to the
footwear, the sole of the footwear introduces a vertical difference between the toe and
the heel. When this is the case, you can either:
Compensate for the sole delta by carefully placing the heel marker with respect to
the toe marker and in the Static Settings dialog box, ensure the check boxes for Left
Foot and/or Right Foot are cleared.
or
Measure the difference in the thickness of the sole at the toe and the heel, in the
Static Settings dialog box, select the check boxes for Left Foot and/or Right Foot
and then in the Properties section at the bottom of the Subjects Resources pane,
enter the delta value in the SoleDelta (mm) box. The height of the heel marker used
in the calculations will then be adjusted accordingly.

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Subject measurements for Plug-in Gait full body model
The following table lists the subject measurements that are used as inputs for running
Plug-in Gait for full body modeling.
Optional measurements are marked with an asterisk in the Name column.
Name

Description

Measure

Left

Right

Body Mass

Patient mass.

_____ kg

Height

Patient height.

_____
mm

*Inter-ASIS

ASIS-ASIS distance is the distance between

_____

distance

the left ASIS and right ASIS. This

measurement is only needed when markers
cannot be placed directly on the ASIS, for
example, in obese patients.
*Head Offset

Patient head offset in degrees.Only

_____ deg

required if head is not level (calculated
after running the Plug-in Gait model).
Leg Length

Full leg length, measured between the ASIS

_____

marker and the medial malleolus, via the

knee joint. Measure with patient standing,
if possible. If the patient is standing in the
crouch position, this measurement is NOT
the shortest distance between the ASIS and
medial malleoli, but rather the measure of
the skeletal leg length.
*ASIS-

ASIS-greater trochanter distance is the

_____

Trochanter

vertical distance, in the sagittal plane,

Distance

between the ASIS and greater trochanter
when the patient is lying supine. Measure
this distance with the femur rotated such
that the greater trochanter is positioned as

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Name

Description

Measure

Left

Right

The medio-lateral width of the knee across

_____

the flexion axis. Measure with patient

The medio-lateral distance across the

_____

malleoli. Measure with patient standing, if

laterally as possible. If this value is not
entered, a regression formula is used to
calculate the hip joint center. If this value is
entered, it will be factored into an equation
which represents the hip joint center.
Knee Width

standing, if possible.
Ankle Width

possible.
*Tibial Torsion

The angle between the knee flexion and

_____

the ankle dorsi-plantar axes. The ankle is

deg

usually externally rotated with respect to
the knee flexion axis. The sign convention
is that if a negative value of tibial torsion is
entered, the ankle flexion/extension axis
will be adjusted from the KAD's defined
position to a position dictated by the tibial
torsion value.
If you are using a KAD, and the medial
malleoli markers are attached to the
patient, Plug-in Gait calculates the tibial
torsion automatically.
*Sole

The difference in the thickness of the sole

_____

Thickness

at the toe and the heel. A positive sole delta

Delta2

indicates that the patient's heel is raised
compared with the toe.

*Thigh

When a KAD is used, this value is calculated

_____

Rotation

to account for the position of the thigh

deg

marker. By using the KAD, placement of the
thigh marker in the plane of the hip joint

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Name

Description

Measure

Left

Right

center and the knee joint center is not
crucial. If you do not use a KAD, this value is
zero as the model assumes that the thigh
marker is placed exactly in the plane of the
hip joint center and the knee joint center.
This value is calculated for you.
*Shank

Similar to the Thigh Rotation. This value is

_____

Rotation

calculated if a KAD is present and removes

deg

the importance of placing the shank marker
in the exact plane of the knee joint center
and ankle joint center. If you do not use a
KAD, this value is zero. It is calculated for
you.
Shoulder

Vertical distance from the center of the

_____

Offset

glenohumeral joint to the base of the

Width of elbow along flexion axis (roughly

_____

between the medial and lateral epicondyles

Anterior (palm side)/Posterior (back)

_____

thickness of wrist at position where wrist

marker on the acromion clavicular joint.
Some researchers have used the (anterior
/posterior girth)/2 to establish a guideline
for the parameter.
Elbow Width

of the humerus).
Wrist Width

marker bar is attached.
Hand

Anterior/Posterior thickness between the

_____

Thickness

dorsum and palmar surfaces of the hand, at

the point where you attach the hand
marker.
1. The tibial torsion measurement is only needed if you are using a KAD.

2.
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2. The Sole Thickness Delta subject measurement is used if the subject is wearing
high-heeled footwear but can keep their foot flat within the shoe. For more
information, see Sole Thickness Delta subject measurement on page 194.
After you have recorded the measurements for your patient, you can create a subject
node for the patient and enter the measurements into Vicon Nexus as described in
Create a new subject from a template on page 110.

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Attach Plug-in Gait markers to a patient
After adding the patient's measurements to the subject node (see Take subject
measurements for Plug-in Gait on page 191), you attach the markers to the patient.
Vicon cameras capture the movement of the retroreflective markers rather than the
body to which they are attached. To enable Nexus to determine the movement of the
subject's underlying skeleton, ensure that the subject's clothing will not occlude
markers or by cause the markers to move excessively. If possible, attach the markers
directly to the patient's skin. During capture, ensure that there is nothing else reflective
in the capture volume.
To attach markers to a patient:
1. Select the appropriate size and quantity of Vicon markers to be used. Typically,
14 mm markers are used for gait analysis studies.
2. Securely attach the Vicon markers to the patient in accordance with the marker
arrangement defined in your chosen template. A front view of the most
commonly used set (for Plug-in Gait lower body modeling) is shown in the
following image. The left lower body markers are not labeled; place markers on
the left side in a similar way to those on the right.

Important
Note that, as shown in the following image, some asymmetry is
desirable as it helps the auto labeling routine distinguish right from left.
In a lower body marker set, you can place the THI and/or TIB markers
asymmetrically. For a full body set, you can place the THI, TIB, UPA and
FRM markers asymmetrically. Similarly, avoid symmetrical placement of
marker clusters or groups of markers and also ensure markers are
asymmetrical within each cluster/group.

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Tip
The THI and TIB markers anterior-posterior position is critical for
identifying the orientation of the knee and ankle flexion axis.
If you are using a single sacral marker (SACR) in a Plug-in Gait lower
body or full body marker set, attach the SACR marker instead of the
two PSIS markers.
Because you need at least three markers to obtain six degrees of
freedom, best practice is to place four markers on the pelvis (LASI
/RASI/LPSI/RPSI), so that even if one of the four markers is occluded
during motion capture, the required three markers will still be visible
to the cameras.

For detailed descriptions and images of marker positions, see Models and

templates in the Plug-in Gait Reference Guide.
You can now capture a calibration trial and reconstruct the markers (see Calibrate a
labeling skeleton on page 113).

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Plug-in Gait Static pipeline
As described in step 5 of Review and finalize a calibration of a labeling skeleton using a
ROM trial on page 120, to enable Plug-in Gait to calculate the static outputs based on
the measured marker positions, you can run a Plug-in Gait Static pipeline on the
reconstructed and labeled static frames of either a ROM trial or a static trial.

Important
The Plug-in Gait Static pipeline is intended to calculate subject-specific
offsets for use as inputs to the Plug-in Gait Dynamic pipeline. If joint angles
are required, you must run the Plug-in Gait Dynamic pipeline (page 203) in
addition to the static pipeline, even for a stationary subject.

Process Static Plug-in Gait Model properties
The following table describes the properties you can specify for the Process Static Plugin Gait Model pipeline operation:
Property

Description

First Frame

Specify the first frame to be used for processing.

Last Frame

Specify the last frame to be used for processing.

Marker Diameter

Specify the diameter of the markers used, assuming they
are applied to the skin's surface. The default is 14mm.

Anterior Thorax Tilt is

Select this option to specify that the anterior thorax tilt is

Positive

positive. Clear this option to specify that the anterior
thorax tilt is negative.

Output Joint Centers

Select this option to visualize the joint centers that are
calculated by Plug-in Gait.

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Property

Description

Assume Horizontal
In this section, you can configure Plug-in Gait to assume that certain markers are at
the same height from the floor during the static trial. Set the appropriate option to
enable Plug-in Gait to compensate for your patient's stance during the static trial.
Important: Set the appropriate foot option if you specify the Sole Thickness Delta
subject measurement because the patient is wearing shoes or orthoses that
introduce a vertical difference between the toe and the heel (for details, see Subject
measurements for Plug-in Gait lower body model on page 192).
Left Foot

Plug-in Gait assumes that the LTOE and LHEE markers are
level with one another. Select this option if the patient's
left foot was flat with the toe and heel in contact with the
floor, even if the left toe (LTOE) and heel (LHEE) markers
were not level with one another.

Right Foot

Select this option if the patient's right foot was flat with
the toe and heel in contact with the floor, even if the right
toe (RTOE) and heel (RHEE) markers were not level with
one another.

Head

Select this option if the patient's head was held level
during the static trial, even if the rear of head markers
(LBHD,RBHD) could not be placed level with the front of
head markers (LFHD, RFHD).

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Plug-in Gait Dynamic pipeline
To enable Plug-in Gait to finalize trial data, including filtering the data, detecting gait
events, and producing a .c3d file for export from Nexus, you can run a Plug-in Gait
Dynamic pipeline on the reconstructed and labeled movement trials.
Before you run the pipeline on your movement trials, ensure you have gap-filled and if
necessary cropped the trials (see Review trials and fill gaps on page 152).
If required, you can change the properties for each of the operations that are included
in the Plug-in Gait Dynamic pipeline. You can also run them individually, and/or run
other operations at this stage too. To help you understand the different operations
typically run on Plug-in Gait movement trials and the options available, each operation
is described in the following topics, together with the Delete Unlabeled Trajectories
pipeline operation, which you may also find useful:
Run the Dynamic Plug-in Gait pipeline on page 204
Delete Unlabeled Trajectories pipeline operation on page 205
Filter Trajectories - Woltring pipeline operation on page 205
Detect Events From Forceplate pipeline operation on page 206
Autocorrelate Events pipeline operation on page 207
Process Dynamic Plug-in Gait Model pipeline operation on page 208
Cross-plate foot strikes on page 210
Export C3D on page 213

Tip
When you are familiar with these operations, you can run all of the data
processing in a single step by creating your own custom pipeline and adding
all the operations described in this section to it, as explained in Create a
pipeline on page 134. When you create your new pipeline, ensure that you
include the operations in the above order.

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Run the Dynamic Plug-in Gait pipeline
To run the Dynamic Plug-in Gait pipeline:
1. On the Data Management tab, ensure the dynamic trial you have gap-filled is
open (for details, see Fill gaps in trial data on page 169).
2. On the Pipeline tab of the Tools pane, from the Current Pipeline list, select
Dynamic Plug-in Gait.
3. Ensure that the required operations are selected and that you have configured
their properties appropriately (see below for details).
4. Click the Play button.
A green check mark appears in the list to the left of each completed operation.
In the 3D Perspective view, the axis for each segment is displayed, together with
the Foot Strike and Foot Off.

5. In the SubjectsResources pane, expand the subject's tree and ensure that the
model outputs are listed.
6. To save the data in .c3d format, on the Vicon Nexus toolbar, click the Save
button.
If you don't need to perform any further processing, you can now export your data. For
more information, see Export trial data on page 233.

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Delete Unlabeled Trajectories pipeline operation
This pipeline operation runs on a fully labeled trial to delete any remaining unlabeled
trajectories. To choose the maximum length of unlabeled trajectory to delete, select
the Delete using Max Length option and specify the Max Length to Delete.

Filter Trajectories - Woltring pipeline operation
This pipeline operation filters the data using the Woltring filter to ensure smooth
trajectories for calculating kinetics. This routine is based on a fifth-order splineinterpolating function (for details on this function and its filtering algorithms, see Plugin Gait references on page 188).
In the Properties pane for this operation, you can specify the following settings:
Property

Description

First Frame

First frame to which filtering is applied

Last Frame

Last frame to which filtering is applied

Filter mode

Choose between:
GCV The filtering routine makes an automatic estimate of the noise
to find the optimal smoothing parameter.
MSE You can change the level of smoothing by entering a different
value for the Smoothing option below.

Trajectories

Enables you to select the trajectories to filter. Can be All trajectories,
All labeled trajectories, or Linked trajectories.

Smoothing

Vicon Motion Systems Ltd.

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Detect Events From Forceplate pipeline operation
This pipeline operation automatically detects gait cycle events such as footstrikes and
adds them to the time bar throughout the trial using vertical ground reaction forces
(GRFs) measured by a force plate connected to the Vicon system. The operation
includes the option to set the force threshold and the label of the markers attached to
the front and back of the foot for both sides.
In the Properties pane for this operation, you can specify the following settings:
Property

Description

First Frame

First frame in which events are detected

Last Frame

Last frame in which events are detected

Force Threshold

The force threshold for automatically detecting heel strike and

(N)

toe off events. The default is 20.

Left anterior

Marker used for event detection. You are recommended to

marker label

leave this at the default setting.

Left posterior

Marker used for event detection. You are recommended to

marker label

leave this at the default setting.

Right anterior

Marker used for event detection. You are recommended to

marker label

leave this at the default setting

Right posterior

Marker used for event detection. You are recommended to

marker label

leave this at the default setting.

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Autocorrelate Events pipeline operation
This pipeline operation detects the pattern of the tracked marker at the set events and
defines these events for the rest of the trial. The available parameters are: marker being
tracked; the X, Y, or Z component of the marker; and the position, velocity, or
acceleration of the marker. Run this operation after Detect Events from Forceplate or
manually entering events on the timebar.
In the Properties section for this operation, you can specify the following settings:
Property

Description

First Frame

First frame in which events are detected

Last Frame

Last frame in which events are detected

Only after

If a force plate is used and you select this option, Vicon Nexus

existing

automatically correlates force plate data events from the time of the
first strike on the force plate and forward. If you do not select this
option, Vicon Nexus automatically correlates events both forward and
backward from the first force plate strike.
If a force plate is not used, you can still select this option, but you
must make a thorough visual check of the events placed.

Marker

Enables you to change the marker used for correlation if necessary.

(Left and
Right)
Component

For walking trials, leave the Left and Right values at the default value

(Left and

(Z). For running and other motor tasks, change as appropriate.

Right)
Derivative

For walking trials, leave the Left and Right values at the default value

(Left and

(Position). For running and other motor tasks, change as appropriate.

Right)

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Process Dynamic Plug-in Gait Model pipeline operation
This pipeline operation runs the dynamic Plug-In Gait model on the active subject of
the current trial.
In the Properties section for this operation, you can specify the following settings:
Property

Description

First Frame

First frame on which the operation is run

Last Frame

Last frame on which the operation is run

Marker diameter (mm)

Ensure the specified value corresponds to the size of the
markers attached to your patient.

Reaction reference

Determines which reference frame is used for reporting

frame

joint moments:
Proximal segment: Reports all moments in the reference
frame of the proximal segment.
Distal segment: Reports all moments in the reference
frame of the distal segment (for example, the tibia
segment for the knee joint).
Global frame: Reports the moment vector relative to the
laboratory coordinate system.

Power Output

How Plug-in Gait is to output the power data:
Standard: The joint power expressed as a single number
(scalar).
Individual Contributions from XYZ: The joint power
expressed as individual X, Y, and Z planes in the
segment's coordinate system

Anterior Thorax Tilt is

Select this option to specify that the anterior thorax tilt is

Positive

positive. Clear this option to specify that the anterior
thorax tilt is negative.

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Property

Description

Output Joint Centers

Select this option to visualize the joint centers that are
calculated by Plug-in Gait.

Allow cross-plate

Select this option when a foot may be in contact with

strikes

more than one force plate simultaneously; for example,
the heel may land on the far side of one plate and then
the toes roll onto the near edge of the subsequent plate.
If you select this option, reactions from the two plates are
combined during processing, with the plate that is struck
first being considered the primary. The forces reported by
each plate are added together; the moments are also
combined by referring the moment from the secondary
plate back to the origin of the primary plate. In effect, the
two plates are treated as a single force plate with the
same origin as the primary plate. For more information,
see Cross-plate foot strikes on page 210.
Although every effort has been made to ensure the
mathematical combination of forces and moments
between two plates is correct, it is the responsibility of
the operator / analyst to review the outcomes produced
by this process and ensure they are correct. Use of this
option in clinical assessments is strictly at the discretion
of the operator/analyst.

Radius of Gyration:

The default radius of gyration for the specified segments.

Pelvis and Thorax

The number is scaled to the length of the segment.
The Plug-in Gait default setting (0.31) means that the
radius of gyration is 31 percent of the segment length.
Only change this setting if you are sure that the default
value is incorrect.

Version

Vicon Motion Systems Ltd.

Plug-in Gait version number.

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Cross-plate foot strikes
To perform an inverse reaction calculation from a foot strike, forces and moments
recorded by a force plate must:
Be assigned to a single context (left or right)
Represent the full forces and moments produced by the subject
In some instances, a foot may be in contact with more than one force plate
simultaneously; for example, the heel may land on the far side of one plate and then
the toes roll onto the near edge of the subsequent plate.

Dynamic Plug-in Gait includes an Advanced option to permit calculations based on
these cross-plate strikes.

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Reactions from the two plates are combined during processing, with the plate that is
struck first being considered the primary. The forces reported by each plate are added
together; the moments are also combined by referring the moment from the secondary
plate back to the origin of the primary plate. In effect, the two plates are treated as a
single force plate with the same origin as the primary plate.
Dynamic Plug-in Gait can automatically detect which foot is activating a force plate by
checking whether the origin of the segment is above the plate. To account for crossplate strikes, the activating area is expanded beyond the bounds of the plate by the
length of the segment (that is, a foot is considered to be above the plate if the ankle
joint center is within a foot-length of the plate boundary).
You may also set the foot strike manually (see Add events to trials on page 180 and
also Automatically assess foot strikes on page 146 ).

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Note that the existing restriction that there must be only a single foot in contact with
any given force plate still applies.

Invalid strike types that do not benefit from the Allow cross-plate strikes
option
Only cross plate strikes can benefit from the Allow cross-plate strikes option; do not
use other invalid strike types for kinetic calculation. The other invalid strike types to
which Allow cross-plate strikes does not apply include:
Double stance plate contacts
Multiple feet simultaneously in contact with a single plate.
In the following example, the left and right foot of a subject contact Force Plate 1 at
the same time.

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Problem: An inability to assign forces to context
Force plate to floor contacts
A single foot strike that transitions from an initial contact with the force plate to the
lab floor or begins on the floor and transitions to a force plate.
In the following example, the heel strikes the force plate but the foot rolls forward off
the force plate and the later stages of foot contact prior to toe off are in contact
with the floor.

Problem: Full forces / moment are not recorded as the some of these are applied to
the floor and not the plate.

Export C3D
This pipeline operation exports the current state of the processed data to a .c3d file.
You can then import the data into other software for further processing or report
generation. For example, in Vicon Polygon you can visualize the trajectories, kinematic
model elements, and kinetics data. If you manually import the corresponding .vst file
into Polygon, it also visualizes the bones. For more information, see Configure the
Export C3D operation on page 238.

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Work with digital video files
If you are using reference video cameras (for example, Vicon Bonita Video or Vicon Vue
cameras), data from these cameras is captured simultaneously with optical motion data
from the Vicon optical cameras.
As video files are large and can take a lot of time to process, to save time and space on
the hard drive, you normally set up the video cameras to save captured video data to
separate, dedicated drives on the host PC, as .vvid files. (For information on video
camera setup, see Configure video cameras for digital video capture on page 61 and
the PDF PC setup for Vicon systems). Note that you cannot view the video in Nexus
until the files are transcoded.
To view the video files, after you have captured and processed your trials, at a suitable
pause in the workflow, you transfer the video files to the host PC, simultaneously
transcoding the files to a format that is viewable in Nexus.
For more information, see:
About transferring and transcoding on page 215
Transfer and transcode digital video files on page 217
De-interlace AVI files on page 220

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About transferring and transcoding
Tip
Because of the size of video files, transferring and transcoding takes up time
and computing resources, so is best done as a batch process on a number of
video files during a break or after the day's capture session ends. Ensure you
transfer, transcode and then delete the .vvid files regularly to avoid filling up
your SSDs.

To enable you to transfer and transcode reference video files, Nexus provides the Show
File Transfer/Batch Processing interface, which you access via a button on the Data
Management toolbar at the top of the Data Management tab.

You can transcode and transfer reference video files to the Nexus host PC that have
been produced by one or more Vicon Vue cameras, Bonita Video cameras, or supported
Basler cameras and recorded to separate drives on the host PC:
Vicon video cameras are easiest to configure and offer higher frame rates than other
supported video cameras.
Supported Basler cameras capture video data in raw format and stream this data
directly to a hard drive. This allows Nexus to capture video as quickly as possible
while minimizing the chances of dropped video frames during collection; however
raw Basler video files are very large, making storage on local hard drives difficult.

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Comparison of vvid files and transfer rates for supported
video cameras
All values are approximate and are provided for guidance only.
Camera type

Width

Height

Frame rate

MB\Sec

Vue (no windowing)

1920

1080

105

Vue (with windowing)

1280

720

120

105

Bonita 720c

1280

720

127

111

Bonita 480m

640

480

360

105

Basler piA640 210 gc

648

488

210

Basler piA1000 48gc\m

1004

Basler A602gc

656

490

100

NTSC DV

720

486

29.97

PAL DV

720

576

Video files are large, so as part of the transfer process, you normally select a codec
(Compressor/Decompressor) format to reduce the video file size. The selection of an
appropriate codec and codec settings ensures the maximum reduction in file size,
while minimizing any reduction in video quality.

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Transfer and transcode digital video files
If a video file within the currently open trial has already been transferred and/or
transcoded, Nexus automatically loads the new version of the file.
To transfer and transcode reference video files:
1. On the Data Management tab, in the Show File Transfer/Batch Processing
interface (see About transferring and transcoding on page 215), click the File
Transfer button.

The list in the Trial column includes all digital video capture trials created during
video capture.
2. From the list, specify the video files to be transferred in any of the following
ways:
Click the corresponding check box to select a specific trial.
Click the Select All button to select all trials in the list.
Click Select None button to clear all previously selected trials.
3. In the File Transfer area, from the Video Compression drop-down menu either
leave None (the default setting) or select one of the supported codecs for
compressing the selected video files prior to transfer. Vicon recommends that
you use the FFDShow codec, which you can download from the Third-Party
Plugins page on the Vicon website. For information on installing and setting the
correct options for the FFDShow codec, see Install the FFDShow codec on page
219.

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Tip
Nexus remembers the last codec selected from the drop-down list.

4. Click the Transfer Files button to start transferring the video files associated
with the selected trials. Any specified transcoding is performed as the first stage
of the transfer process.

Caution
Do not attempt to capture data while a file transfer is in process.
Interrupting this process may result in problems with the data capture
or file transfer. Allow the file transfer process to complete, or click the
Cancel Transfer button to manually stop the process before starting a
new capture.

During the transfer, the progress column in the trials list indicates the transfer status:
Blank : File transfer process idle
Yellow moving bar: File transfer process in progress
Green static bar: File transfer process successfully completed
Red static bar: File transfer process failed or canceled
In addition, the File Transfer counter enables you to check easily on the progress of the
transfer of large numbers of video files.

The counter displays both the number of the current video and the total number of
videos that are being transferred.

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Install the FFDShow codec
The FFDShow codec is recommended by Vicon for transcoding your raw video files.
To install this codec:
1. Visit the Third-Party Plugins page on the Vicon website.
2. Click on FFDShow Codec and download the file.
3. Install the downloaded FFDShow.exe file.
4. Accept the default options, ensuring that on the Select Components screen, the
VFW Interface option is selected.
5. Click Start > All Programs > ffdshow > VFW Configuration.
6. On the Encoder tab, ensure Generic is selected, then select the following options
and click OK:
Encoder: MPEG-4
FOURCC: XVID
Mode: one pass - average bitrate
Bitrate (kbps): 900
Maximum I frame interval: 10
Minimum I frame interval: 1
7. In Nexus, you can now select the FFDShow codec from the list of available
codecs in the File Transfer area of the Data Management tab.

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De-interlace AVI files
Nexus can permanently de-interlace all interlaced .avi files associated with the
currently loaded trial. The de-interlaced .avi file is placed in the same directory as the
source .avi file. It retains the original file name, but is appended as follows: [filename].

interlaced.avi.
If an .avi file within the currently open trial has been de-interlaced, Nexus automatically
loads the new (de-interlaced) version of the file.

Important
Audio tracks are not transferred to the de-interlaced file.

To de-interlace an .avi file:
1. To load a digital video file, with the Camera view selected, click on the desired
movie file on the Data Management tab.
2. In the Available Operations section of Pipeline Tools pane, expand the System
pipeline operations list.
3. Double-click the Apply Codec to Video pipeline operation.
The operation is added to the current pipeline and is displayed at the bottom of
the list in the Current Pipeline section.
4. In the Current Pipeline section, click on the pipeline operation, and then in the
Properties section at the bottom of the Pipeline Tools pane:
a. From the drop-down Video Codec list, select the codec you want to use for
file compression.

Important
Due to the rapidly changing nature of available capture hardware,
PC processing power, and available codecs, please check the
third-party downloads on the Vicon website for the latest
recommended codec (currently FFDShow).

b. If you want Nexus to create a backup of the video file, ensure the Keep
Backup option is selected.

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b.

Important
Reverting to the backup file to re-do the de-interlacing is not
supported in Nexus. Therefore, Vicon recommends that Keep
Backup remains selected whenever you permanently de-interlace
an .avi file.
To perform de-interlacing again on a video file, you must reimport the file and rerun the pipeline operation.

c. From the Remove Interlacing list, select the required option.
5. Add any other pipeline operations you want to include in the pipeline.

Tip
The pipeline operations are run in the order they appear in the Current
Pipeline list; you can rearrange the order by dragging operations into
the desired position in the list.

6. In the Current Pipeline configuration management section, click the Save button
to save your settings. (An asterisk (*) is displayed next to the pipeline name if
there are unsaved changes.)
7. Run the pipeline.

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Work with IMUs
If you are using Vicon IMUs (Inertial Measurement Units) with Nexus, first ensure you
have set up the IMUs and Nexus as described in Configure IMUs on page 89.

For information on working with IMUs, see the following topics:
Capture IMU data on page 223
Manage your captured IMU data on page 225
Transfer data from IMUs on page 227
Export IMU data on page 228
Import data from the IMeasureU Research app on page 229
Calibrate IMUs on page 231
Pair an IMU to a different device on page 232

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Capture IMU data
1. Having have set up the IMUs to work with Nexus (see Configure IMUs) on page
89, capture in the usual way (see Capture the required movement on page 137
).
While the IMUs are connected to Nexus, a real-time preview of data streaming
from the IMUs is displayed. This preview data stream is supplied to Nexus at 50
Hz, regardless of the trial collection rate (100 Hz, 250 Hz, 500 Hz or 1000 Hz).
You can view this preview data in Live mode in Nexus.

The preview stream is optimized for low latency data visibility and may therefore have small frame
gaps where data does not appear.
When trial capture starts, the IMU simultaneously enables the display of preview data at 50 Hz and
writes data to its internal memory.

Note
Gaps in the preview data do not indicate gaps in the data that is written
to memory.

When you stop a trial capture, an .x1d file that contains the preview data that is
displayed in the Graph view is saved into the current Session folder and is
displayed with a purple A icon on the Data Management tab.

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2. When you have finished capturing data, plug the IMUs into your PC using the
supplied USB cables.

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Manage your captured IMU data
After you have finished capturing data and have plugged the IMUs into the PC, you use
the IMeasureU tab in the Nexus Communications pane to work with the data and
transfer it.

Tip
To help you decide whether to transfer recorded data, you can check the
preview data by playing it in Offline mode first.

To display the IMU data, in the Communications pane, click the IMeasureU tab.
The connected IMUs and the trials that were recorded onto them are listed.
Depending on what you want to do with the data that you have captured, choose the
appropriate option.
To do this

Take this action

Select one or more trials

Click, SHIFT+click or click Select All
After you have transferred trials (see Transfer data
from IMUs on page 227), you may want to use Select
Transferred, or Select Untransferred.

Remove selected trials

Select the trials that you want to remove and click Re

from the Transfer list.

move Selected Trials.
The trials are removed from the Transfer list, but
remain on the IMU.

Remove from Nexus all

Select the the IMUs that you want to remove and

references to selected

click Remove Selected Devices.

IMUs and their related
trials.

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The selected IMUs and their trials are removed from
the Transfer list, but the trials remain on the IMUs.

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To do this

Take this action

Remove from one or more

Select the the IMU(s) that contains the trials that you

IMUs all collected trials,

want to remove and click Erase Selected Devices.

and remove the IMU and its
trials from the Transfer list.

Transfer trial data from the

All data is removed from the selected IMU(s) and the
IMU is removed from the Transfer List.
See Transfer data from IMUs. on page 227

IMUs to the Session folder
in Nexus on your PC.

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Transfer data from IMUs
To transfer the data from the IMU(s) to the Session folder in Nexus:
1. Ensure you have downloaded and installed the CP210x USB to UART Bridge VCP
Drivers.
2. On the IMeasureU tab, in the Transferlist, select the required files for transfer to
the Session folder.
3. At the bottom of the pane, click the Transfer Files button.
When transfer is complete, the Progress column in the Transfer list changes to
Transferred for the IMUs and for each successfully transferred trial.

After the transfer operation, for each trial, you can find the following files in the
Session folder:
An .x1d containing the preview data (50 Hz)
An .imu file containing the higher quality data (100 Hz, 250 Hz, 500 Hz or
1000 Hz) from the IMU
4. You can now view and process the IMU data along with the rest of the trial data.

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Export IMU data
You can export data captured using IMUs by running the appropriate pipeline.
To export IMU data:
1. If you want to select data from only some devices, in the System Resources pane,
ensure the required IMUs are selected.
2. In the Pipeline Tools pane, expand File Export and double-click Export ASCII to
add it to the current pipeline.
3. In the Properties pane, ensure that the settings are as required. In the Devices
section, if necessary, change the Devices for Export list to specify your selection.
4. Run the Export ASCII operation.
To open the exported file in Microsoft® Excel®, on the Data Management tab,
click the relevant C icon and then click the filename.

The data is displayed in an Excel spreadsheet.

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Import data from the IMeasureU Research app
You can capture data using IMeasureU Research app and then import the downloaded
CSV files from Lightning into Nexus.
To work with IMU Research input:
1. On the Data Management tab, make sure you have selected the session into
which you want to import your IMU Research files.
2. On the IMeasureU tab, in the Import section enter or browse to the relevant
folder to import the CSV file(s) that you downloaded from Lightning.
If you have downloaded multiple files to sub-folders, select Create trials from subfolders.
3. In the Trial Name field, enter a name for the trial that will be imported. If
required, select the options to automatically increment the trial numbers and/or
overwrite existing trials with the same name.

4. Click Create Trial.
Files with the extension .x1d are created in the location you selected in Step 1.
You can view IMU Research data in the Graph pane in Nexus.

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Calibrate IMUs
IMUs are already calibrated when they are supplied to you, and the calibration is stored
on the IMU, so you only need to re-calibrate when you update the camera firmware or if
an offset of the IMU occurs.
Note that IMUs can be calibrated at 100 Hz only.
To calibrate IMUs:
1. Select the IMU(s) that you want to calibrate and in the Properties pane, ensure
Advanced properties are displayed.
2. Ensure that the IMUs are static and are not subject to vibration, and positioned
with the Z+ axis pointing up or down.
3. In the General section of the Properties pane, click Calibrate Sensor.

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Pair an IMU to a different device
After an IMU is paired with a Bluetooth® (BLE) dongle (central device), the IMU will only
work with that dongle and will reject requests from other central devices (built-in
Bluetooth or BLE dongle). To pair the IMU with a different central device (eg a dongle
on a different Windows computer), you must erase the stored connection information.
To erase stored connection information:
1. Turn on the IMU and plug it into the PC via USB.
2. Before downloading any data, on the IMeasureU Lightning toolbar, click Clear
Bluetooth.

This deletes the stored connection information. At the bottom left of the screen
a message confirms that the cache has been cleared.
You will not have to repeat a pairing operation unless you:
Remove or reconfigure your Bluetooth receiver (unplug the dongle etc...)
Manually remove the pairing

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Export trial data
During your work with Vicon Nexus, you can export data for use in other software.
Nexus offers a number of options for data export, accessible from the Available
Operations list in the Pipeline Tools pane and from some view panes.
You can also export a video file (.avi) from a 3D or Camera view.
For more information, see:
Configure file export pipeline operations on page 234
Export 3D workspace as AVI on page 239

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Configure file export pipeline operations
You view and change the settings for the supplied export pipeline operations in the
Properties pane at the bottom of the Pipeline Tools pane. For more information, see:
Configure the Export 3D Overlay Video operation on page 234
Configure the Export ASCII operation on page 236
Configure the Export C3D operation on page 238
You can also export to a number of other file formats: to view the available formats, in
the Pipeline Tools pane, go to the Available Operations list and expand File Export.
For general information about how to use pipelines, see Work with pipelines on page
131.

Configure the Export 3D Overlay Video operation
You can export the 3D overlay of Vicon optical data over images from a supported
calibrated video camera to an .avi file for viewing in other applications using the Export
3D Overlay Video operation in the Pipeline Tools pane.
With the Combined View option in a Camera view, you can display Vicon optical data
overlaid onto images from a calibrated digital video camera. For example, you can
display 3D information, such as the floor grid, markers, and virtual force plates,
overlaying the 2D video image. The Export 3D Overlay Video operation burns this 3D
overlay information into an .avi (digital video file) so that you can view it in other
applications, such as Vicon Polygon.
To export 3D overlay information to an .avi file:
1. In the Camera view toolbar, from the View drop-down list select Combined to
view Vicon optical data overlaid onto images from a digital video camera.
2. In the Options dialog box (F7), select the desired options to configure the
visualization of data to suit your needs (for example, you may want only the force
vector to appear on the 3D overlay).
3. At the top of the Options dialog box, click the Save button to save the
configuration you just created. The configuration is saved as an .options file in
the appropriate Nexus Options folder.

4.
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4. In the Pipeline Tools pane, create a File Export pipeline that includes the Export
3D Overlay Video operation. (For a reminder of how to create a pipeline, see
Create a pipeline on page 134.)
5. In the Current Pipeline operations list, click on the operation, then in the
Properties section at the bottom of the Pipeline Tools pane, view or change
settings for the desired properties:
From the View Options Set list, which is displayed in alphabetical order, select
the name of the .options file you created in step 3.
If required, select an option from the Video Codec list. (If you want to deinterlace the .avi file, you must select an appropriate codec.)
If the trial is cropped, select the appropriate range of frames to export. If you
do not do this, the exported video will be of the whole trial, but will be static in
the cropped frames.
6. Run the pipeline either on an individual trial in the Pipeline Tools pane or on
multiple files using the Batch Processing Interface (click Show File Transfer
/Batch Processing interface

and then the Batch Processing button

the Data Management tab).

About 3D overlay files
The 3D overlay information from each DV camera is stored in a separate file, in the
format: TrialName.DeviceID.overlay.avi where:
TrialName is the base name of the trial file.
DeviceID is the unique identification number Vicon assigns to a DV camera.
You can find the Device ID in the System Resources pane, by expanding the Video
Cameras node, selecting the desired video camera, and then in the Properties section
expanding the Settings area.
overlay identifies the file contents as the 3D overlay information associated with the
video file.
avi is the file extension.

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For example, with a video camera with a Device ID of 52883644, if you run the Export
3D Overlay Video pipeline operation on a video file named Walk1.52883644.avi, the
exported 3D overlay file will be called Walk1.52883644.overlay.avi.

Note
You cannot open an exported 3D overlay (.overlay.avi) file in Nexus.

Configure the Export ASCII operation
The Export ASCII pipeline operation enables you to export saved trial data to a plain
text file, saved in CSV or TXT format.
To export processed Nexus data to an ASCII file:
1. Ensure you have loaded and processed the required data.
2. In the Pipeline Tools pane, create a File Export pipeline that includes the Export
ASCII operation. (For a reminder of how to create a pipeline, see Create a pipeline
on page .)
3. In the Current Pipeline operations list, click on the operation, then in the
Properties section at the bottom of the Pipeline Tools pane, view or change
settings for the desired properties:
Flename: Do one of the following:
Accept the default Current Trial setting; or
To use a different path and/or filename, click the downward arrow to the
right of the box, clear the Macro check box, and click the ellipsis (...). You
can then enter the required file name, including its extension, for example
my_trial.csv.
File Extension: Can be .csv, .txt, or if required, clear the Macro check box as
described above and then specify the required extension.
First Frame and Last Frame: If required, change these to specify the range that
you want to export.
Delimiter: Do one of the following:
Click to choose the delimiter of the exported data, selecting either commas,
tabs, or line feeds/carriage returns; or

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To use a different delimiter, click the downward arrow and clear the Macro
check box. You can then edit the Delimiter field to specify a combination of
ASCII characters (maximum of two characters).
Local Numeric Format: If you want the exported data to use the local language
float number format, select this check box.
Export Gait Cycle Parameters: To export gait cycle analysis, select this option.
Export Events: To export events, select this option. If you choose to include
events, they are sorted in the output file by type, subject and time of
occurrence.
Digital Device Sampling: Choose the digital devices frame rate and sampling
rate options:
MX Frames: Exports at the same frame rate as the trajectory data. The
exported data may be up-sampled to achieve an integer number of subsamples per frame.
Raw Frames Exports at the original frame rate and sample rate. The exported
frame and sub-frame numbers may not correspond to other devices or the
trajectory data.
Local Numeric Format: To export using the local language's float number
format, select this option.
For the rest of the outputs, you can do one of the following:
Click to choose to export either none, only the selected output type, or all of
them; or
To supply a comma-separated list, click the downward arrow to the right of
the drop-down list and clear the Macro check box.

Tip
In most cases, as an alternative to selecting All, you can use the asterisk
* wildcard.

4. Either run the pipeline or right-click the Export ASCII operation and click Run
selected op.
5. After you have run the pipeline operation and exported the file, you can examine
the exported data as required.

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Configure the Export C3D operation
This pipeline operation exports the current state of the processed data to a .c3d file.
You can then import the data into other software for further processing or report
generation.
In the Properties section you can view or change the following properties:
Filename Name of the file to be exported. By default, this is the name of the current
trial, for example Trial01. To change the name, click the downward arrow to the right
of the field and clear the Macro check box. You can then enter a new name.
First Frame First frame of the range to be exported
Last Frame Last frame of the range to be exported
Trial Name Postfix Adds the string you specify to the end of the filename. For
example, if you entered export in this field, the name of the output file would be
Trial01.export.c3d.
Integer Format Measures the maximum range between real data points, and
determines a scale factor. The data is then scaled to that range when saved to the
c3d file, and all values are written with the Integer format. When the data is read into
another program (eg Polygon), the scale factor is applied to the data, converting it
into Real data. The Real data format saves the data as it is, without any multiplication
by a scale factor, and writes it to the c3d file.
Certain types of data are best suited for the Real format option because no
resolution is given up in the storage of the data. However, bear in mind that not all
programs can read both Integer- and Real-formatted c3d files. For more details on
the .c3d format, see c3d.org.
Subject Prefixes Prefixes the exported marker labels with the subject's name. (To
specify that marker labels are prefixed only when more than one subject's data is
exported, choose the Auto option.)
X Axis Direction, Y Axis Direction, Z Axis Direction Enables you to choose the
direction of the axis in the exported 3D world.

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Export 3D workspace as AVI
The Export 3D Workspace as AVI button in the Camera view, 3D Perspective and 3D
Orthogonal views lets you easily create visually rich content for presentations or for use
in other third-party applications.
Nexus enables you to create video files of a selected 3D workspace.
Before you export a workspace, ensure you have:
Loaded a trial.
Installed the desired video compression codec.
To export a workspace as an AVI:
1. Ensure Nexus is not in Live mode.
2. In the workspace, click the Export Workspace to AVI button.

3. In the Export Workspace to AVI dialog box, enter the required information and
then click OK. Note that Image Width and Image Height refer to the resolution
(in pixels) of the exported image.

A progress bar indicates the status of the export process and by default, a video
file with the same name as the current trial is created in the trial session folder.
(You can change the name and location if required.)

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Nexus
User
Guide

Further resources
If you need more information than that supplied in the documentation or
on the Vicon Support web pages, please contact Vicon:
Denver, CO

Los Angeles, CA

Vicon Denver

Vicon LA

7388 S. Revere Parkway, Suite 901

3750 S. Robertson Boulevard, Suite 100

Centennial

Culver City

CO 80112

Los Angeles

USA

CA 90232

T: 303.799.8686

USA

F: 303.799.8690

T: 310.437.4499

E: support@vicon.com

F: 310.388.3200
E: support@vicon.com

Oxford, UK
Vicon Oxford
Unit 6, Oxford Industrial Park
Mead Road, Yarnton
Oxford
OX5 1QU
United Kingdom
T: +44.1865.261800
F: +44.1865.240527
E: support@vicon.com

Vicon trademarks

Vicon Motion Systems Ltd.

26-Oct-2018

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