Radeon Open-Source Vulkan Driver Enables Ray Queries By Default

Written by Michael Larabel in Radeon on 24 May 2022 at 05:26 AM EDT. 3 Comments
What started out as hopes of enabling RADV ray-tracing by default has led to initially ray queries being enabled by default.

Konstantin Seurer has enabled Vulkan ray queries support by default within the RADV driver for Mesa 22.2. Last month KHR_ray_query support was added to RADV as the latest of their Vulkan ray-tracing effort. Ray queries was successfully tested with various demos, the GravityMark benchmark, Quake II RTX, and more. But like the RADV ray-tracing support at large, was disabled by default unless using the "RADV_PERFTEST=rt" environment variable to enable the extensions.

The Mesa developers have determined that the ray queries support at least is in good enough shape to enable by default. With today's Git activity, ray queries and acceleration structure builds are enabled by default for RDNA2 cards (Radeon RX 6000 series).

Meanwhile this change also alters the option for emulating the Vulkan RT extensions for older GPUs. The "RADV_PERFTEST" flag for enabling the RT emulation was previously "force_emulate_rt" but now is set as "emulate_rt" to enable, should you be wanting to try Vulkan RT usage on older Radeon GPUs.

RADV's ray-tracing support continues to improve as an alternative to the official Vulkan RT support within AMD's proprietary, cross-platform Vulkan driver. AMD's open-source AMDVLK driver meanwhile still isn't exposing any of the ray-tracing support.

The hope with the default enabling is to lead to more user testing and bug reports to further harden the RADV ray-tracing support. Per the MR, "Ray queries and acceleration structure builds are quite stable now and so we can enable those features for CI and more feedback and bug reports."

The RADV_PERFTEST=rt environment variable can be used for enabling all Vulkan ray-tracing extensions still for the time being on RDNA2 GPUs. This default enabling of ray queries will be found in next quarter's Mesa 22.2 release unless too many problems are exhibited where they could still revert this change.
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