Gallium3D/R600 Support For Texture Multisample

Last month I wrote about Mesa support for the ARB_texture_multisample. At the time the support was limited to enabling this OpenGL extension for the Intel Mesa DRI driver with Gallium3D and its hardware drivers going unsupported. Fortunately, the OpenGL texture multi-sample support is now heading to Gallium3D and is close to being in a good state for the AMD "R600g" driver.

David Airlie shared on Sunday morning his new "gallium-texture-multisample" Mesa branch that works out the Gallium3D/R600 support for this OpenGL feature. The GL_ARB_texture_multisample extension is part of the OpenGL 3.2 specification. From the OpenGL.org registry, this NVIDIA-developed extension is described as:

This extension provides support for two new types of "multisample textures" - two-dimensional and two-dimensional array - as well as mechanisms to fetch a specific sample from such a texture in a shader, and to attach such textures to FBOs for rendering. This extension also includes the following functionality, first described in NV_explicit_multisample:

* A query in the API to query the location of samples within the pixel
* An explicit control for the multisample sample mask to augment the control provided by SampleCoverage

Hopefully this GL_ARB_texture_multisample work will be ready for merging into the forthcoming release of Mesa 9.1.

Initial feedback on the R600 texture multi-sample code can be found on the Mesa developers' mailing list. The Mesa branch with this support can be found on FreeDesktop.org.