A configuration for defining when a Material is considered being alpha tested.
RayTracingAccelerationStructure.CullInstances can specify a RayTracingSubMeshFlags value associated with alpha tested Materials to determine the behavior of Meshes or individual sub-meshes that use these Materials when building an acceleration structure, or when performing ray tracing.
For example, Meshes that use alpha tested Materials can simply use RayTracingSubMeshFlags.Enabled flag in RayTracingInstanceCullingConfig.subMeshFlagsConfig structure for alpha tested Materials which will allow the GPU to invoke an user-defined any hit shader when a ray intersects the geometry. The any hit shader can perform an alpha test and decide whether there was a valid ray-geometry intersection or not.
Additional resources: RayTracingInstanceCullingConfig.subMeshFlagsConfig.