The big new feature with AMD HIP RT 2.2 is adding support for multi-level instancing, which becomes important for rendering larger scenes while being constrained by the available video memory.
AMD engineers have also been working to get the PBRT-v4 ray-tracer running on AMD GPUs. With their PBRT-v4 fork they have now managed to successfully get the popular Disney Moana Island Scene rendered using HIP RT with a Radeon PRO W7900 graphics card:
HIP RT 2.2 also brings compaction for geometry and scenes, optimized construction speed, and other optimizations.
Downloads and more details on the HIP RT 2.2 release via GPUOpen.com .