"Substantial Progress" With Mesa Geometry Shaders

Open-source Intel developers have advanced their OpenGL geometry shaders work for Mesa, namely for the Intel DRI driver, and call it "substantial progress and definitely a reason to celebrate." This important GL3 feature is nearing a working state but there's still some work ahead before it will be merged.

Earlier this week I wrote about progress on Gallium3D LLVM geometry shaders that was done by Zack Rusin at VMware while Intel for the past few months has also been hard at work on their classic Mesa DRI driver support. Geometry shaders are one of the important features to OpenGL 3.2 and one of the remaining items left before the specification is implemented by this open-source project.

The last major update out of Intel on the matter was a number of weeks back when it wasn't ready. Intel OTC's Paul Berry now says though that as of yesterday he has a work-in-progress back-end for the i965 "Gen6" Ivy Bridge hardware that now passes his 1800+ geometry shader test cases within Piglit. "I rebased Bryan Cain's front-end patches onto Mesa master, made a minor bug fix or two, and spent the next month and a half beginning to implement a geometry shader back-end for i965 Gen7 (Ivy Bridge). I'm happy to report that as of this morning, my work-in-progress back-end, combined with Bryan's front-end, passes all the piglit tests I introduced in mid-February."

However, this work isn't yet living in mainline Mesa and needs to be cleaned up and re-based. Berry explains, "This is substantial progress and definitely a reason to celebrate, but there is still a lot of work to do before we can expose ARB/EXT_geometry_shader4 support on i965 Gen7, mostly in the back end...I don't want to land any patches until there are adequate piglit tests for them, so my next order of business is to write additional tests to exercise corner cases of the ARB/EXT_geometry_shader4 spec. Once those are complete, I will start sending out my rebase of Bryan Cain's front-end patch series for review. After Bryan's series has landed, I'll start sending out the i965 Gen7 back-end for review."

Only after the OpenGL ARB/EXT_geometry_shader4 extension is fully implemented for Mesa on Ivy Bridge, will Paul begin work on "Gen6" Sandy Bridge support. More details can be found within this mailing list message.