Unity sample project using instancing and per-instance shader properties in Ray Tracing.
The project uses RayTracingAccelerationStructure.AddInstances function to add many ray tracing instances of a Mesh to an acceleration structure. The project doesn't use a render pipeline or rasterization.
Resource binding for hit shaders is done through shader tables and shader records. Writing shader records can be an expensive CPU operation when Materials are complex and use many resources and properties. When using AddInstances function, all ray tracing instances associated with the specified Mesh will use the same shader record which can notably improve CPU performance.
In hit shaders, per-instance shader properties are accessed using the difference between HLSL intrinsic InstanceIndex() and built-in shader variable unity_BaseInstanceID. For example:
uint instanceID = InstanceIndex() - unity_BaseInstanceID;
Check MeshInstancing.shader where per-instance color is read from a buffer.
RayTracingInstanceData.cs computes per-instance transformation matrices and colors.
After opening the project, switch to Game view and press Play to animate the geometries.
- Windows 10 version 1809 and above.
- GPU supporting Ray Tracing (SystemInfo.supportsRayTracing must be true).
- Unity 2023.1.0a18+.