AMD R600g Is Making Progress With Tessellation, Running Heaven

Thanks to work by Red Hat's David Airlie, the R600 Gallium3D driver is very close to having OpenGL tessellation support, which will then allow this pre-GCN AMD open-source driver to expose OpenGL 4.1 compliance.

Airlie wrote on his Google+ page, "After much typing, pain and hw errata, finally got heaven with tessellation enabled to render on an AMD radeon evergreen class card with the Mesa r600g driver. ARB_tessellation_shader is at least within striking distance and hence OpenGL 4.1 for at least some classes of radeon Evergreen/Northern Island cards with the open source driver. Much cleanup required to upstream it, but at least I have a working point to roll back to."

The OpenGL R600g tessellation support is currently in this Git branch. As David mentioned, it still needs to be cleaned up and such before being merged to Mesa, but at least it's now functioning out-of-tree.

The GL_ARB_tessellation_shader is the lone extension left blocking R600g from achieving OpenGL 4.0 compliance and the necessary OpenGL 4.1 changes are already complete, so once tessellation lands, R600g will be capable of OpenGL 4.1. However, this is only for select Radeon HD 5000/6000 series graphics cards. In the end the only cards with R600g that will be able to happily live with OpenGL 4 are likely the Cypress and Cayman GPUs, a.k.a. the Radeon HD 5800 series and Radeon HD 6900 series.