https://devblogs.microsoft.com/directx/dev-preview-of-new-directx-12-features/ "...we continue to work with both GPU vendors and game developers to better expose hardware capabilities and to better address adoption pain points. As a result, we will introduce DXR tier 1.1 with the following new
additions on top of tier 1.0. - Support for adding extra shaders to an existing Raytracing PSO, which greatly increases efficiency of dynamic PSO additions. - Support ExecuteIndirect for Raytracing, which enables
adaptive algorithms where the number of rays is decided on the GPU execution timeline. - Introduce Inline Raytracing, which provides more direct control of the ray traversal algorithm and shader scheduling, a less
complex alternative when the full shader-based raytracing system is overkill, and more flexibility since RayQuery can be called from every shader stage. It also opens new DXR use cases, especially in compute: culling,
physics, occlusion queries, and so on. DXR tier 1.1 is a superset of tier 1.0..."