The Broadcom V3DV VideoCore open source Vulkan driver in Mesa has rewritten the code related to hardware obscuration queries to significantly improve performance and reliability.
Iago Toral has rewritten the V3DV masking query code to improve the performance of the VideoCore Vulkan driver. Our implementation relies heavily on the CPU to do things like query resets and result replication, and some aspects of query availability tracking are handled by the CPU,” he explained in the merge request.
This new implementation handles all GPU-side query functions by scheduling compute shaders, which involves query availability, resets, and result replication. Currently, this approach only supports managing shading queries, but in the future some additional work could be done to implement Performance queries.
As an improvement to the open source Raspberry Pi Raspberry Pi graphics driver, more than 1000 lines of rewritten V3DV driver code have been merged into Mesa 23.0.
Hardware occlusion queries are features of the 3D API that tell an application whether pixels will be drawn when rendering an object. When the wraparound box is occluded, the drawing of objects inside the wraparound box is skipped. Although the feature exists, there are still two issues that affect its widespread use: the overhead of resolving the occlusion query itself and the delay in waiting for the query result.
