Intel's ANV Vulkan Driver Aiming For Transform Feedback In Mesa 19.0, Helping DXVK

With Mesa 19.0 entering its feature freeze in three weeks, the race is on for finishing up OpenGL/Vulkan driver changes to make it in this next quarterly installment of these 3D open-source Linux graphics drivers.

In addition to potentially landing the SPIR-V Clover support in time for Mesa 19.0, Intel ANV lead developer Jason Ekstrand has commented on the changes he would like to see happen in time for this first release of 2019.

Ekstrand expressed interest in seeing two changes: code to stop using Userptr for state pools and VK_EXT_transform_feedback. VK_EXT_transform_feedback was added to Vulkan 1.1.88 last October for Stream-Output / transform feedback functionality similar to OpenGL and Direct3D. This is an unofficial extension designed to help efforts like DXVK for mapping Direct 3D 11 to Vulkan and also relevant to other graphics APIs with similar functionality that this transform feedback support can now be easily provided.

While NVIDIA shipped a supported beta driver that very day and RADV did later in October, the Intel ANV driver (as well as AMDVLK) have been the main Linux Vulkan drivers not yet implementing this extension. In the case of ANV, they had patches available from the start but didn't merge them yet over lacking test coverage -- particularly for the Vulkan Conformance Test Suite (CTS).

DXVK immediately began utilizing this Vulkan extension and Zink is another project that does have a code branch providing support for this extension in order to provide OpenGL transform feedback. Zink is the project providing OpenGL atop Vulkan. With more projects expected to make use of this extension but even just DXVK's use of it being big, hopefully the Intel ANV driver will land its transform feedback support for Mesa 19.0.

Mesa 19.0 is branching at the end of January and will be available as stable a few weeks after that depending upon the number of release candidates required.