Algorithm of OpenGL tessellator

[rufusz]

Hi all,

I need to write a paper about tessellation at my university and as chapter 1 I need to describe/explain how the "standard" tessellation works. Since OpenGL is open source, I suppose also the algorithm/maths behind it are also free. Maybe it is written somewhere but I didn't find it.

Thx for any help

[martinsm]

OpenGL is not open-source. OpenGL is API specification open to anybody.
Currently tesselation in OpenGL is available only as vendor specific extension AMD_vertex_shader_tesselator (http://www.opengl.org/registry/specs/AMD/vertex_shader_tessellator.txt).

[rufusz]

Wow, thats new information :)

Do you happen to know where can I find additional information on this theme? Basically I have to describe how video cards (GPUs) display primitives (spheres,etc) using triangulation. What algorithms are used, etc. First I've thought the answer is in the Catmull-Clark subdivision surfaces, but I was pointed out that that algorithm is used for mesh refining, not for approximations with lower polycount meshes.

[ZbuffeR]

Hardware GPUs only display triangles.
Any other primitive must be described with triangles by the CPU program.

Maybe you had something else in mind, like GLU tesselation ?
http://glprogramming.com/red/chapter11.html

There is an open source implementation of GLU in Mesa3D:
http://cgit.freedesktop.org/mesa/mesa/tree/src/glu/sgi/libtess