[UniteKorea2013] The Unity Rendering Pipeline
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The document discusses the Unity rendering pipeline and provides tips for optimizing shaders and rendering in Unity. Some key points: - The Unity rendering pipeline is very flexible but can be difficult to configure for specific needs and targets. - Built-in shaders are good for standard lighting models but not for stylized games or maximum performance. Custom shaders may be faster. - Shader combinations allow using keywords to control shader variants. Material keywords make this configurable per object. - Lit shader replacement and tags allow swapping shaders at runtime while keeping material properties. - DX11 features like tessellation, random writes, and volume textures provide more flexibility but require custom shaders.
![Multiple render targets
• In the script do: (javascript)
// rt1, rt2, rt3, rt4 are RenderTextures
// create an array of color buffers
var mrt4 : RenderBuffer[] = [ rt1.colorBuffer, rt2.colorBuffer, rt3.colorBuffer, rt4.colorBuffer ];
// set those color buffers and the depth buffer from the first render texture as the current target
Graphics.SetRenderTarget (mrt4, rt1.depthBuffer);
// draw your stuff!
[...]](https://image.slidesharecdn.com/theunityrenderingpipelinekuba-130505193137-phpapp02/85/UniteKorea2013-The-Unity-Rendering-Pipeline-46-320.jpg)
[UniteKorea2013] The Unity Rendering Pipeline
- 1. The Unity Rendering Pipeline Kuba Cupisz (Tim Cooper) Texthttp://is.gd/RenderingPipeline_UniteAsia13
- 2. Who am I? • Kuba • graphics programmer • at Unity for... quite.some.time • worked on small game projects before
- 3. Topics What Unity is good/bad at Built-in shaders Shader combinations Per material keywords Lit shader replace Endless runner with light probes DX 11 Tessellation Random writes Volume textures
- 4. What is Unity good at • Very flexible rendering pipeline • vertex lit / forward / deferred • custom shaders • custom lighting models • completely customizable
- 5. What is Unity bad at • Very flexible rendering pipeline • difficult to configure (so.many.options) • Some parts are better maintained then others • dual lightmaps in forward • Default settings do not suit all projects • very general, scale from mobile to high end • aim your configuration at your target
- 6. Built-in shaders - good for • Work with all rendering configurations • forward / deferred, realtime lighting / lightmaps • Support standard lighting models • lambert / blinn-phong • Work on all platforms
- 7. Built-in shaders - not good for • Stylized games • only provide ‘standard’ lighting models • Super-performance • if you know how your game will look, you can write more specific (faster) shaders • Size • always have many shader variants due to supporting many possible configurations
- 8. When to write your own? • When the built-in shaders • are not custom enough • are not fast enough - don’t assume, profile! • you know exactly how you want your game to be rendered
- 9. Shader combinations • Compile variants of your shader • to do different things based on keywords • shader keywords are set globally • can be overridden per material
- 10. Shader combinations • Each line declares a set of defines • only one per line can be active at a time • Make sure you enable one, otherwise Unity will pick one for you
- 11. Shader combinations #pragma multi_compile AAA BBB • two variants • one where AAA is defined • another where BBB is defined (and AAA is not)
- 12. Shader combinations #pragma multi_compile AAA BBB #pragma multi_compile CCC • two variants • AAA CCC • BBB CCC
- 13. Shader combinations #pragma multi_compile AAA BBB #pragma multi_compile CCC DDD • four variants • AAA CCC • BBB CCC • AAA DDD • BBB DDD
- 14. Per material keywords • Shader keywords property on a material • array of strings • each string a keyword • Write a custom editor to make it easy to use
- 15. Material inspector • Extend the MaterialEditor class • Override OnInspectorGUI() • remember to call base.OnInspectorGUI() !
- 16. Shader combinations example • Surface shader • 2 defines • 1 for darken blend mode • 1 for difference blend mode • configured via material inspector
- 17. Shader combinations • Applications • switch the shaders in your scene via a keyword • completely change the look of your game • in the future • one shader for: diffuse, specular, normal maps, etc.
- 18. Shader replace • Objects normally get rendered with whatever material /shader is configured on them • Using shader replace you can swap out the shader • still uses same material (so textures / properties will be the same as in the original rendering) • Sub-shader is selected based on tag-matching
- 19. Shader replace - Tags • When setting a replacement shader, you can set the tag • Camera.SetReplacementShader (Shader s, string tag) • Camera.RenderWithShader (Shader s, string tag)
- 20. Shader replace - Tags • No tag specified? • all objects will be rendered with the replacement shader • uses the first subshader of the replacement shader
- 21. Shader replace - Tags • Tag set? • the real object’s shader is queried for the tag value • no matching tag? • not rendered • tag found? • subshader from the replacement shader selected which matches the tag
- 22. Tags • Builtin, e.g. RenderType: • Opaque • Transparent • TransparentCutout • etc. • Custom • whatever you want!
- 23. Lit-Shader replacement • New in Unity 4.1 • Useful for • scene view enhancement • special effects • How does it work? • just like normal shader replace! • but you can use shaders that have lighting passes (surface shaders!)
- 24. Endless runner with light probes • The track is assembled from blocks • Any block can be matched with any other block • It’s not feasible to bake light probes for all the combinations of block setups
- 25. Endless runner with light probes • Bake light probes for each block separately • After baking, light probes are tetrahedralized • When the player moves from one block to the other you want to switch to light probes for the new block • set Lightmapping.lightProbes
- 26. Smooth transition • Just switching from one light probe set to another will give a pop • Solution: • make sure that start and end light probe positions have the same layout • when loading the new probes, set the start probes in the new set to the end probes of the previous set
- 27. Smooth transition • Transition distance • add another set of light probes relatively closely to the start probes to control the transition distance
- 28. Baked data is not movable • Loaded light probes will show up at the positions where they were baked • in our case the blocks’ pivots are at (0,0,0) • If you’d use player’s position to sample light probes you’d sample outside of the volume defined by the probes -- not good
- 29. Baked data is not movable • Luckily you can set lightProbeAnchor on the renderer to a transform of choice • Parent the transform under the player • Set local offset to -currentBlocksOffset on block change
- 30. DX 11 • Gives you more flexibility • Allows for techniques that were impossible to do on the GPU before and not feasible on the CPU
- 31. Tessellation • What is tessellation • subdivision of geometry • adds more triangles • by default in the same plane as the original triangle, so doesn’t add more detail yet
- 32. Tessellation • To get more detail, tessellate and: • displace by sampling a displacement texture, or • use Phong tessellation • inflates the geometry and smooths the silhouette
- 33. Tessellation with surface shaders • Use tessellate:FunctionName modifier in the surface shader declaration • float FunctionName () { return tessAmount; } • built-in • UnityDistanceBasedTess • tessellate more close to the camera • UnityEdgeLengthBasedTess • tessellate big triangles more
- 34. Random writes • Unordered Access View • for RenderTextures or ComputeBuffers • allows writing at any position within the buffer
- 35. Random writes • RenderTexture • generally stores colors • bajilion different formats • ARGB32, ARGBHalf, ARGBFloat, R(8|Half|Float), etc.
- 36. Random writes • ComputeBuffer (StructuredBuffer in DX11) • stores structs or simple types • could be color, of course • int, float, you name it
- 37. Random writes • Create a ComputeBuffer from script • provide the count and the stride (size of one element in bytes) • Initialize the contents using SetData() • Set the buffer for a material using SetBuffer()
- 38. Random writes • In the shader declare the buffer as • StructuredBuffer<your_data_type> • random reads • RWStructuredBuffer<your_data_type> • random reads and writes
- 39. Random writes example • Image analysis • run a shader on the scene render • analyze each pixel and write to an output buffer at a location of your choice • you can also atomically increment the value • InterlockedAdd() • requires a buffer of ints or uints though
- 40. Volume textures • You know how textures are normally in 2D?! • Now they are in 3D! • BOOM
- 41. Volume textures • How does DX 11 come into play? • you can fill the volume texture from a compute shader really quickly (do it each frame?)
- 42. Volume textures example • Fills in the volume texture based on dispatch thread ID* • combined thread and thread group index * Read up on semantics on MSDN
- 43. Questions? • Kuba @kubacupisz • Tim @stramit
- 44. Appendix
- 45. Multiple render targets • In the shader do: • void frag(v2f i, out float4 Colour0 : COLOR0, out float4 Colour1 : COLOR1) or • make the pixel shader return a color array or • make the pixel shader return a struct with COLOR0...COLORn semantics
- 46. Multiple render targets • In the script do: (javascript) // rt1, rt2, rt3, rt4 are RenderTextures // create an array of color buffers var mrt4 : RenderBuffer[] = [ rt1.colorBuffer, rt2.colorBuffer, rt3.colorBuffer, rt4.colorBuffer ]; // set those color buffers and the depth buffer from the first render texture as the current target Graphics.SetRenderTarget (mrt4, rt1.depthBuffer); // draw your stuff! [...]