After writing yesterday about the most interesting work in this three-month update to Mesa, here's a look at some of the features that will not be found within the imminent release of Mesa 10.2:
- OpenGL 3.3 / Geometry Shaders for Sandy Bridge. Intel Sandy Bridge hardware is technically capable of achieving OpenGL 3.3 compliance, but only OpenGL 3.1 is advertised currently by recent releases of Mesa (including v10.2) and the Intel Windows OpenGL driver also only advertises OpenGL 3.1 support. The main blocker to OpenGL 3.3 compliance for Sandy Bridge is geometry shaders support. As pointed out by open-source Intel Linux developers in the past, OpenGL GS support could be written to get Sandy Bridge OpenGL 3.3 support, but from Intel there's not much interest -- the developers have more important work and are much more interested in adding features to their fresh hardware rather than the now-old Sandy Bridge. In the end it's left up to the community developers if they want to add this support.
- Open-source 3D/OpenGL support for AMD Radeon R9 290 "Hawaii" GPUs remains broken. Basic OpenGL support for the high-end AMD Radeon R9 290/290X was briefly working before in the past, but somewhere in the stack it's regressed and isn't working. AMD Linux developers acknowledge they don't know why the support isn't working and that "Hawaii support is not a priority at the moment."
- The open-source OpenCL support within Gallium3D's "Clover" state tracker still leaves a lot to be desired. Some basic OpenCL apps are now working within the open-source Radeon stack, but it's not an enormous number of CL applications, the support outside of Radeon hardware is mixed, and there isn't many Linux distributions (any major ones?) shipping this open-source OpenCL support. The first major Linux distribution going after good out-of-the-box open-source OpenCL support will be Fedora 21.
- There's still legal issues surrounding the use of S3TC texture compression, OpenGL floating-point textures, and other patent issues for having fully-featured open-source OpenGL drivers.
- The performance is still generally slower than proprietary graphics drivers. For the latest-generation Haswell graphics, the Intel Linux driver is slower than Intel's Windows 8.1 driver. On the Radeon side the R600/RadeonSI Gallium3D driver is catching up to Catalyst with around ~80% the performance of Catalyst. On the Nouveau side for open-source NVIDIA support, the main limitation is on the kernel side with the Nouveau DRM driver still lacking proper re-clocking support.
- The OpenGL support is still far from matching the upstream Khronos OpenGL specifications. We aren't yet at OpenGL 4.0 compliance while the latest upstream specification is at OpenGL 4.4, which has been out for one year, and will likely be succeeded soon. Hopefully there will be core Mesa support for OpenGL 4.0 in 2014... The current support matrix can be found via the Mesa docs.
Anything else you're looking for out of the open-source Mesa 3D driver stack? Let us know via the forums!