Mesa Gets Closer To Having OpenGL 4.0 Tessellation Support

A significant patch-set was published on Saturday night that implements the driver-independent bits of OpenGL 4's ARB_tessellation_shader extension inside Mesa.

The tessellation support has been one of the big pieces missing from Mesa's OpenGL 4 implementation and fortunately it's getting close to mainline. Chris Forbes of Intel published fifty-six patches this weekend that implement the driver-independent portions of the extension inside Mesa. Of course, the driver portions still need to follow for it to be useful.

Chris wrote, "This series adds all the driver-independent bits for ARB_tessellation_shader. It's not quite finished, and there are still a handful of ugly hacks to remove, but I think it's complete enough to start getting some review feedback."

For those unfamiliar with OpenGL tessellation, the OpenGL.org registry explains, "This extension introduces new tessellation stages and two new shader types to the OpenGL primitive processing pipeline. These pipeline stages operate on a new basic primitive type, called a patch. A patch consists of a fixed-size collection of vertices, each with per-vertex attributes, plus a number of associated per-patch attributes. Tessellation control shaders transform an input patch specified by the application, computing per-vertex and per-patch attributes for a new output patch. A fixed-function tessellation primitive generator subdivides the patch, and tessellation evaluation shaders are used to compute the position and attributes of each vertex produced by the tessellator."

Intel is getting very close with Mesa on OpenGL 4.0~4.2 compliance.