The index buffer that Unity uses to define geometries used by ray tracing instances.
You can use a common index buffer as a pool to define multiple geometries used by ray tracing instances that have different properties (for example different materials). Use subGeometries array to configure index ranges for each geometry.
Specify GraphicsBuffer.Target.Raw for the Target parameter when you create the index buffer from scripts. If the buffer is also used in rasterization, then add the GraphicsBuffer.Target.Index flag.