OpenGL tessellation test

A crude benchmark of the new OpenGL tessellation shaders, using the utah teapot.

The teapot (made out of bezier patches as usual) is rendered at various subdivision levels, with the framerate being visible thanks to frapix.

On the left, the bezier patches are being evaluated at the various subdivision levels in the CPU, and the final quads are passed to OpenGL for drawing. On the right side, the bezier patches are tessellated and evaluated on the GPU, with the new programmable tessellation control and tesselation evaluation shader stages of the OpenGL pipeline (ARB_tessellation_shader).

Public domain source code. Also see notes at the end.

subdiv	CPU bezier eval	GPU bezier eval
1
2
4
8
16
32
64

Notes

The benchmark is really crude, though I believe, representative. Here's a list of what's wrong with this benchmark:

Immediate mode drawing, probably adds more function call overhead to the software version, than to the GPU tessellation version.
The software version is flat-shaded to illustrate the tessellation level, while the GPU version calculates full per-pixel illumination, with a ton of normalizations in the fragment shader, and does an additional mod/smoothstep calculation to draw uv iso-contours for the same reason.