Mesa Makes More Strides Towards OpenGL 3.x Support

The OpenGL 3.0 specification was announced in August of 2007 and has already been succeeded by OpenGL 3.1, OpenGL 3.2, and then earlier this year came OpenGL 3.3 and OpenGL 4.0. While the 3.0 revision to this industry standard graphics API has been around for nearly three years, it's still not fully supported by the open-source Mesa graphics stack. Progress though is being made.

Mesa still lags behind greatly with OpenGL 3.x (and now, OpenGL 4.0) support along with the respective GLSL (GL Shading Language) updates that have come in tandem. There was also supposed to be an OpenGL 3.1 state tracker for Gallium3D that's been talked about for more than a year, but it has yet to emerge. Originally, patents were blamed as a hurdle in providing full OpenGL 3.x support within Mesa, but support for the new OGL3 extensions have been coming slowly. Once there is proper OpenGL 3.x support within Mesa's core (at least within the software portion, not necessarily implemented by Gallium3D or the DRI hardware drivers) it will be released as Mesa 8.0, but it seems we're still a way from reaching that point.

VMware's Brian Paul announced a new branch of Mesa last night that brings one new OGL3 extension: GL_NV_primitive_restart. The GL_NV_primitive_restart extension became part of the Khronos specification with OpenGL 3.1, but has been a NVIDIA extension going back to 2002.

GL_NV_primitive_restart allows OpenGL applications to restart a primitive in its middle. According to its extension specification, "The typical expected use of this feature is to draw a mesh with many triangle strips, though primitive restarts are legal for all primitive types, even for points (wherethey are not useful)." Compared to other primitive restart methods, GL_NV_primitive_restart is supposed to be more lightweight.

The GL_NV_primitive_restart extension isn't yet supported in the mainline Mesa code-base on Git for the Mesa 7.9 release, but right now it's living in a branch called primitive-restart. With this initial implementation by Brian Paul, GL_NV_primitive_restart support isn't added to any of the hardware drivers, but it is implemented for the Gallium3D softpipe driver and also the faster software method of using the LLVMpipe driver when combined with a modern CPU.

Hopefully the GL_NV_primitive_restart extension support will be merged to master in the near future. The current state of the OpenGL 3.x/4.0 support in Mesa core can be found in this Git text file. There's many OpenGL 3.0 features supported by the latest Mesa code like conditional rendering, map buffer sub-ranges, frame-buffer objects, packed depth/stencil formats, and vertex array objects. However, there are many areas of the OpenGL 3.0 specification that still haven't been touched like the new GL Shading Language improvements, GL_EXT_texture_compression_rgtc support, GL_EXT_framebuffer_sRGB support, half-floats, and other features. The later revisions to OpenGL 3.x are even further behind and right now there is no OpenGL 4.0 support that's been started for Mesa.