Indirect Rendering With Compute Shaders
An example of drawing numerous instances in Unity3D using Compute shaders and Graphics.DrawMeshInstancedIndirect.
This project has only been tested on a Macbook Pro using Metal. When using DirectX, it is very likely you need to add the arguments buffer into the instance rendering shader and add the offset to unity_InstanceID to get the correct instance.
- Quasirandom squences to place the instances
- Use compute buffers and compute shaders
- Draw things using Graphics.DrawMeshInstancedIndirect
- GPU Sorting with Bitonic sorting
- Compute shader: Frustum culling
- Compute shader: Occlusion culling with HierarchicalZBuffer
- Compute shader: LOD objects using the distance from camera to object
- Extending camera frustum towards light to include shadow casting objects
- "_Example.cs" script on the "Example" game object:
- Creates the instance data and sends it to the Indirect Renderer class.
- "IndirectRenderer.cs" on the "MainCamera" game object:
- Is the main class in the project. It initializes all the buffers and compute shaders and then dispatches the compute shaders and draws the objects when Unity calls the PreCull() function.
- "HiZBuffer.cs" script on the "OccluderCamera" game object:
- Creates a hierarchial Z-Buffer texture that is used when doing occlusion culling.
- Improve the instance sorting:
- On my Macbook pro (mid 2014) sorting takes approx 50% of the GPU time
- The GPU sorting must support instance numbers that are not in the non power of two (right now I'm padding the data to become POT)
- Find a better performant approach for the CPU Sorting
- Try to make the compute buffers smaller in size. Ex: Pack the three floats, used for bounds size, into one uint.
- Try out Raster Occlusion instead of Hi-Z (See "NVidia Siggraph 2014" & "Github - nvpro-samples" below)
- Try and profile structure buffers with structs divisible by 128 bits (sizeof float) => https://developer.nvidia.com/content/understanding-structured-buffer-performance
Copyright (C) 2017-2018 Elvar Orn Unnthorsson
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