"This sample is basically a performance test for particle systems, which allows you to switch between three different methods of creating eye-rotated billboards. For the first method, billboard calculations are done manually and take place totally on the CPU by the application. For the second method, the particle system uses ARB_point_sprite extension to offload the creation of billboards to the GPU. And finally, the third method uses Cg to build billboards on the GPU via a vertex shader." And, a bunny.
