Aura Starting Guide
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Starting Guide 16/2/2017 Raphael Ernaelsten @RaphErnaelsten Table Of Contents Table Of Contents 1 About Aura 5 TL;DR; 5 Overview 7 Glossary 8 Getting Started 9 Set the Aura Main Component 9 Add Aura Lights 10 Add Aura Volumes 10 Aura Main Component Base Injection Tab Ambient Injection 12 12 12 Ambient Density 12 Ambient Anisotropy 12 Ambient Light 12 Ambient Light Strength 12 Settings Tab 13 Grid 13 Horizontal/Vertical/Depth 13 Range 13 Contribution 13 Experimental Features 13 Enable Occlusion Culling 13 Occlusion Culling Accuracy 13 Enable Reprojection 13 Reprojector factor 13 Aura Lights Base Parameters Tab 13 15 Strength 15 Override Color 15 Enable Shadows 15 Enable Cookie 15 Additional Parameters Tab (Directional Light) 15 Enable Out-Of-Phase Color 15 Strength 15 1 Additional Parameters Tab (Spot Light) 16 Angular Attenuation 16 Threshold 16 Exponent 16 Distance Attenuation 16 Threshold 16 Exponent 16 Distance Attenuation 16 Threshold 16 Exponent 16 Cookie Fade-In Attenuation 16 Fade-In Thresholds 16 Exponent 16 Additional Parameters Tab (Point Light) Distance Attenuation 17 17 Threshold 17 Exponent 17 Aura Volumes Settings Tab Volume Shape 17 18 19 Shape of the Volume 19 Parameters 19 Falloff Exponent 19 Noise Mask 19 Enable 19 Speed 19 Offset 19 Transform 19 Texture Mask 19 Enable 20 Texture 20 Transform 20 Warp Mode 20 Filter Mode 20 Clip on Alpha 20 Clipping Threshold 20 Density Tab 20 Enable 21 Strength 21 Texture Mask Levels (if Texture Mask) 21 2 Levels Thresholds 21 Contrast 21 Output Low Value 21 Output High Value 21 Noise Mask Levels (if Noise Mask) 21 Levels Thresholds 21 Contrast 21 Output Low Value 21 Output High Value 21 Color Tab 21 Enable 21 Strength 22 Texture Mask Levels (if Texture Mask) 22 Levels Thresholds 22 Contrast 22 Output Low Value 22 Output High Value 22 Noise Mask Levels (if Noise Mask) 22 Levels Thresholds 22 Contrast 22 Output Low Value 22 Output High Value 22 Anisotropy Tab 22 Enable 23 Strength 23 Texture Mask Levels (if Texture Mask) 23 Levels Thresholds 23 Contrast 23 Output Low Value 23 Output High Value 23 Noise Mask Levels (if Noise Mask) 23 Levels Thresholds 23 Contrast 23 Output Low Value 23 Output High Value 23 Illuminate/Fog Particles 24 Using Aura in your Shaders 25 Requirements 25 Acknowledgement 27 Special Thanks 27 3 License TL;DR; FAQ 27 28 28 Why releasing Aura for free? 29 Can we make donations? 29 Will Aura’s development be continued? 29 Will Aura support the Scriptable Render Pipeline? 29 Does Aura work on Unity xxx? 29 Does Aura support VR? 29 Why did it take so long? 30 How can we help you developing Aura? 30 How can I keep updated about Aura? 30 4 About Aura TL;DR; What Aura is : ● a local (within a defined distance from the camera) simulation of the light scattering into the surrounding medium What Aura is not: ● an atmospheric scattering simulation ● a cloud simulator Aura is an open source volumetric lighting solution for Unity. The development is hosted on GitHub and the latest package is published on the Asset Store. Aura simulates the scattering of the light in the environmental medium and the illumination of micro-particles that are present in this environment but invisible to the eye/camera. This effect is also called “volumetric fog”. The directional light is scattered into the air and illuminates the invisible micro-particles. Aura uses a globalist approach that makes every lights and injection volumes interconnected. This means that when you locally modify the environment somewhere, it will 5 automatically affect all the lights and injection volumes. No boring and redundant per-instance setup ... Also, all lights and injection volumes are dynamic and then, can be created, modified or destroyed at runtime. Aura packs a bunch of features such as full lighting support, injection volumes and particles illumination. Click here to view the recap of all the features of Aura (on YouTube). 6 Overview Aura relies on Bart Wronski (@BartWronsk)’s Presentation and particularly the idea that the volumetric lighting could be solely computed in the frustum and pre-integrated in a 3D texture. Starting from that, 7 additional points were targeted : 1. Dynamic quality (not fixed ones) 2. Ease of use (not hours of integration or many parameters to struggle with) 3. Make it cascaded (for further range) -> Not implemented yet but bases are set 4. Use Unity’s full lighting system (not only one directional light) 5. Use injection volumes (locally modify the density, lighting and scattering) 6. Illuminate Unity’s particles (to have macro and micro particles volumetric lighting) 7. Plug other processes (so we could have volumetric GI, custom smoke, …) Here’s the schematic overview of Aura’s internal process : Click here to visit the online API Documentation. Please note that Aura is meant to be an evolving project. Importing updates might require re-tweaking, re-assigning Aura components or deleting the asset’s folder prior importing. 7 Glossary This document will often refer to specific words that worth a bit of contextualization. Medium The environmental matter that fills the environment and which the lights will scatter in. Typically it will be air, water or glass; but can be more exotic gases/liquids/solids in your convenience. Density This is the amount of invisible micro-particles that fill the medium. It can also be understood as the “fog factor”. Color (or Light Color) The tint and intensity of volumetric light that is in a particular point. Anisotropy This represent the scattering factor the light will undergo from its emission through the camera. 0 means that there is no scattering and that the light will travel straight to the camera without loss. 1 means that the light will be totally scattered in all directions before reaching the camera. In other words, it controls how much the volumetric lighting concentrate around the light source. Tips : This can practically be useful to simulate the amount of humidity of the medium (0 = dry medium, no scattering; 1 = humid medium, maximum scattering). Note that this is not a general rule, just an interpretation tip. The best way is always to try. 8 Getting Started Set the Aura Main Component Always set the Aura Main Component on the Camera GameObject (see Aura Main Component section). The default values are purely for visual feedback. The process should be thought as iterative, adding one element after another. Following that guideline, the ambient data should be set as low as the medium would be. For example, if we want to simulate air, starting with a very low Ambient Density factor is a good starting point as, often, surrounding air is not much foggy. Let’s set it to 0.025. Then, we will evaluate the wetness of the air and express it through the Ambient Anisotropy factor. This can range from (nearly) 0 very dry air like in deserts, to (nearly) 1 very humid like in a dampy cave. Let’s set it to 0.8. Finally, we will have to assess the Ambient Color and its Strength, in other terms, the minimum lighting value in the medium. Pretty much like the usual ambient lighting, this can be thought as the lighting that will be in the shadows. For our example, being in a forest-ish environment, we will set the color to a low saturated green and the strength to a small value as it’s supposed to be in the shadows, 0.45 will do. 9 Add Aura Lights We can now add/assign Aura Lights in the scene (see Aura Lights section). In our example, we will just modify the out-of-phase color in order to tint the light to a bluish color when the light is scattered (or when the light ray is not around the light source). Add Aura Volumes We can also add Aura Volumes in the scene (see Aura Volumes section). In our example, we will put one Aura Planar Volume to add more fog down the hill, in the woods. To do so, we will add Density (the amount of fog) and modify the Anisotropy (to simulate variations of humidity and catch the eye). On top of that we will use a Noise Mask so it doesn’t look like a solid block but more like a smoky/cloudy place. 10 Click here to see this example in the On/Off Comparison video (on YouTube). 11 Aura Main Component First thing to do to get started is always to set the Aura Main Component on the Camera GameObject. This will start the whole volumetric computation process and set the ambient data for the volumetric lighting. After having assigned the Aura Main Component, any amount of Aura Light or Aura Volume can be added in no particular order. The Aura Main Component is composed of two tabs of parameters. Base Injection Tab Ambient Injection The "Ambient Injection" parameters set the starting Density, Color and Anisotropy of the environment. Ambient Density The starting amount of fog in the medium. Ambient Anisotropy The starting light scattering factor of the medium. Ambient Light The tint of the starting volumetric lighting of the medium. Ambient Light Strength The intensity of the Ambient Light. 12 Settings Tab Grid Allows to determine the density of cells used to compute the volumetric lighting. Horizontal/Vertical/Depth The resolution of the grid. Range The maximum distance within which the volumetric lighting will be computed. Contribution Allows to enable/disable what type of contribution will be computed. Note that the existence of the different contributions are handled by the system at runtime. Experimental Features These features are still at experimental stage. This means that, although stable, they can lead to visual artifacts. Enable Occlusion Culling Allows to compute the maximum visible depth of the frustum grid. This leads to avoid computing cells that are invisible to the camera because hidden behind objects. Occlusion Culling Accuracy The precision used to determine the maximum visible depth. Enable Reprojection Allows to blend the current (jittered) computed frame with the previous one. This leads to a smoother volumetric lighting, especially with a low resolution grid. Reprojector factor Controls the scale and amount of reprojection. 13 Aura Lights The Aura Light components can be assigned on the Lights you want to be taken into account into the volumetric lighting computation. Aura Lights can also be directly created using the GameObjects menu. The default value of the Aura Light components are normalized to fit Unity’s lighting system. Therefore, leaving a strength factor of 1 for the volumetric lighting will closely fit the strength of the surface lighting of Unity’s lighting system. The Aura Light component is composed of two tabs. One for the common parameters, whatever the type of light; one with additional parameters that will change regarding the type of the light. 14 Base Parameters Tab Strength The intensity of the volumetric lighting computed from the light. Override Color Allows to ignore and replace the color of the light for the volumetric lighting. Enable Shadows Enables the computation of the shadows of the light in the volumetric lighting (if the light casts shadows). Enable Cookie Enables the computation of the cookie of the light in the volumetric lighting (if the light has a cookie). Additional Parameters Tab (Directional Light) Enable Out-Of-Phase Color Allows to cancel the extinction of the light when it goes scattered and replace it with a color. Strength The intensity of the Out-Of-Phase Color. 15 Additional Parameters Tab (Spot Light) Angular Attenuation Allows to tweak the fade-out of the light from the center to the outer border of the cone. Threshold Normalized angle when the fade will start, until 1. Exponent Curve of the fading. Distance Attenuation Allows to tweak the fade-out of the light within its range. Threshold Normalized distance when the fade will start, until 1. Exponent Curve of the fading. Distance Attenuation Allows to tweak the fade-out of the light within its range. Threshold Normalized distance when the fade will start, until 1. Exponent Curve of the fading. Cookie Fade-In Attenuation Allows to tweak the fade-in of the light’s cookie within its range. Fade-In Thresholds Normalized range where the cookie will fade in. Exponent Curve of the fading. 16 Additional Parameters Tab (Point Light) Distance Attenuation Allows to tweak the fade-out of the light within its range. Threshold Normalized distance when the fade will start, until 1. Exponent Curve of the fading. 17 Aura Volumes Aura Volumes can be added into the scenes to locally modify one or several of the base ingredients of Aura’s system (Density, Color and Anisotropy). Aura Volumes can be directly created using the GameObjects menu. The Aura Volume component is composed of four tabs. 18 Settings Tab The settings tab will allow to tweak the shape and the border attenuations of the Volume. Noise and Texture masks can also be enabled to modulate the injections parameters. Volume Shape Shape of the Volume Select the volumetric shape of the Volume between : ● Global ● Planar ● Box ● Sphere ● Cylinder ● Cone Parameters Allow to tweak the fading on the borders of the shape, allowing a smooth transition between the inside and the outside of the volume. Falloff Exponent Curve of the fade-out attenuations. Noise Mask Enable Activates the dynamic noise mask and applies it on the Density, Color and Anisotropy injections. Speed Speed of the morphing effect. Offset Offset of the morphing effect, in order to desynchronize noise that have the same speed. Transform Allows to set (and animate) the position, rotation and scale of the noise. 19 Texture Mask Enable Activates the volumetric texture mask and applies the RGB channels data on the Color injection and the Alpha channel on the Density and Anisotropy injections. Texture The source Texture3D to use. Transform Allows to set (and animate) the position, rotation and scale of the volumetric texture. Warp Mode Sets how the texture should warp outside the 0-1 coordinates range. Filter Mode Set how the volumetric texture should be filtered when displayed. Clip on Alpha Allows to bypass computation of the Volume cell based on the Alpha channel. Clipping Threshold Threshold under which the Volume cell will be bypassed. 20 Density Tab Enable Allows to add/remove fog inside the Volume. Strength The amount of fog to be added. This value can be negative, meaning that fog can be removed. Texture Mask Levels (if Texture Mask) Remaps and contrasts the texture mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. Noise Mask Levels (if Noise Mask) Remaps and contrasts the noise mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. 21 Color Tab Enable Allows to add/remove light inside the Volume. Strength The intensity of the light to be added. This value can be negative, meaning that light can be removed. Texture Mask Levels (if Texture Mask) Remaps and contrasts the texture mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. Noise Mask Levels (if Noise Mask) Remaps and contrasts the noise mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. 22 Anisotropy Tab Enable Allows to add/remove anisotropy inside the Volume. Strength The amount of anisotropy to be added. This value can be negative, meaning that anisotropy can be removed. Texture Mask Levels (if Texture Mask) Remaps and contrasts the texture mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. Noise Mask Levels (if Noise Mask) Remaps and contrasts the noise mask value. Levels Thresholds Clamps the lower and upper range of the value. Contrast Contrasts the clamped value. Output Low Value Remap the upper threshold of the value to a new value. Output High Value Remap the lower threshold of the value to a new value. 23 Illuminate/Fog Particles Since Aura stores and sends the punctual and accumulated volumetric lighting as global buffers, it is easy to retrieve them if we know the element’s position inside the frustum. That is how the particles illumination and fog work with Aura. If you want to illuminate/fog your particles with Aura, you can choose between the provided shaders or make your own, following the provided ones as examples. 24 Using Aura in your Shaders In the same idea as the particles illumination/fogging, Aura can be implemented in your own custom shaders (transparent or not) in 3 very piece-of-cake steps. 1. Include “Aura.cginc” located in the “Aura/Shaders/” folder. 2. In the Vertex Shader, compute the position inside the Aura frustum with void Aura_ApplyLighting(inout float3 colorToApply, float3 screenSpacePosition, float lightingFactor) 3. You can now apply the volumetric lighting with the following method void Aura_ApplyLighting(inout float3 colorToApply, float3 screenSpacePosition, float lightingFactor) and/or apply the fog with the following overloads void Aura_ApplyFog(inout float3 colorToApply, float3 screenSpacePosition) void Aura_ApplyFog(inout float4 colorToApply, float3 screenSpacePosition) 25 Requirements Aura strictly requires full support of the following elements to work : ● RenderTextures (3D as well) ● Texture2DArrays ● ComputeShaders Please verify that the support of these elements is not limited especially on lower platforms. Aura release was targeted for Unity 2017.2 : - older version will not be supported (although I can help making it work ;-) ) - newer version will be supported with updates if necessary Historically, Texture2DArrays were introduced in Unity 5.4 which makes it the lowest version compatible with Aura. However, multi-threaded ComputeShaders compilation was introduced in Unity 2017.2 which makes it the advised minimum version (as the main ComputeShader in looong to compile with its many variants). 26 Acknowledgement Aura uses the following works : ● Bartlomiej Wronski (@BartWronsk)’s presentation : “Volumetric Fog : Unified compute shader based solution to atmospheric scattering” ● Sebastien Hillaire (@SebHillaire)’s integration formula : “Physically Based and Unified Volumetric Rendering in Frostbite” ● Ashima Arts’s 4D Simplex Noise : https://github.com/ashima/webgl-noise About the provided demo scene : ● Marko Dabrovic’s Sponza scene : http://hdri.cgtechniques.com/~sponza/files/ ● Unity Lab’s smoke spritesheet : “VFX Image Sequences & Flipbooks” Please let me know if I forgot any reference. Special Thanks For their time and help, I would like to cheerfully thank : ● Bartlomiej Wronski (@BartWronsk) ● Florent Guinier (@FlorentGuinier) ● Sebastien Lagarde (@SebLagarde) ● Gil Damoiseaux (@Gaxil) ● All the people that helped me by testing Aura, and kept me motivated with their constructive feedbacks and their kind words. 27 License Aura is released under MIT License. Please refer to the license.txt file located in the Aura/License folder for the full license. TL;DR; - You can sell and make money with your projects that use Aura (or any derived form) You can do whatever you want with Aura but not sell Aura (or any derived form) You must propagate this license There is no warranty of any kind Please consider crediting Aura (or any derived form) in your projects, with the provided logo if relevant 28 FAQ Why releasing Aura for free? For several reasons : ● Aura was actually never meant to be sold. It was a personal challenge I set to myself. When people asked me about its price, I was just answering that such a solution would be worth around 40$. ● I am a self learner. Half of the knowledge I have is from dissecting sources from people that shared them. I wanted to give this opportunity back to the community. As a Teacher I really feel like this is a good deed. ● I just want to make the Unity community thrive and make Unity better on my own level. Can we make donations? I didn’t expect that, thank you! You can click on the following button or the button on the GitHub front page. Will Aura’s development be continued? Hopefully yes! At least until Unity drops the legacy lighting system. Furthermore, I still have a bunch of feature ideas to implement, fixes and todos. Will Aura support the Scriptable Render Pipeline? Anyhow, all this work cannot stop with the end of the legacy pipeline. So yes, my plan is to make it work with the SRP for the long term continuation. It may however be part of another branch/repository. Does Aura work on Unity xxx? The technical requirement for Aura are specified in the Requirements section. The minimum version possible for Aura is Unity 5.4 but the release is targeted for 2017.2. Does Aura support VR? I did not test it myself but apparently Aura works out-of-hands with multi-view VR. Single-pass doesn't work for now but is under investigation. 29 Why did it take so long? Aura was a personal project, a challenge for myself. It was developed during my free time. I am a full-time Technical Art Teacher and aside, we released our game (Outcast Second Contact) a few months ago. This, combined with my family life gives a pretty good idea of the amount of time I was able to manage for Aura. How can we help you developing Aura? There are many ways you can help me facilitating the development of Aura : ● You can spread the words about Aura. ● You can branch the repo, improve the code, develop new features, fix bugs, ... I’ll merge with the Master if relevant. ● You can share your work made with Aura (on my Twitter) or tips using Aura. ● You can make a demo scene and send it to me. (Make sure to own the content of it so I can publish it in the package) ● You can make a donation, like previously said. ● Anything that can help making Aura a great project! How can I keep updated about Aura? Two sure possibilities : ● Follow me on Twitter (@RaphErnaelsten) ● Wait for the updates of the package on the Asset Store. 30
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