Radeon RADV Ray-Tracing Performance Further Improved - PLOC BVH Builder

In recent months there has been a lot of RADV ray-tracing optimizations and improvements for maturing the ray-tracing support by this open-source Radeon Vulkan driver within Mesa. The RADV ray-tracing performance is about to take another step forward with a pending merge request providing a PLOC BVH builder that can improve the Quake II RTX performance by around 33%.

Friedrich Vock and Bas Nieuwenhuizen have been working on this Parallel Locally-Ordered Clustering (PLOC) support for building bounding volume hierarchy nodes (BVHs). Vock commented that it uses in-shader global synchronization and a task partitioning algorithm similar to GPURT. GPURT is notable in being AMD's open-source GPU ray-tracing project that recently enabled Vulkan ray-tracing for AMDVLK, AMD's official open-source Vulkan Linux driver and an alternative to Mesa's RADV. It's good to see GPURT being helpful to RADV at least for ideas.

Friedrich Vock commented in the merge request around the performance benefits of this PLOC BVH builder:

"My benchmarking on a 6700XT indicates a 33% uplift for Q2RTX and the nvpro demos. Control suffers a bit from the increased build times, but still gets a tiny bit better (around 47 -> 51 FPS)."

A 33% boost for Quake II RTX and NVIDIA Vulkan RT demos is quite encouraging. The merge request for this RADV RT feature was opened yesterday while we'll see how the code review goes and if this several hundred lines of new code manages to land ahead of the Mesa 22.3 feature freeze / branching that is happening in early November.

UPDATE (31 Oct): It's now merged.