The Post-Clip Primitives metric represents the number of primitives that flowed out of the clipper. The metric includes original primitives that passed the trivial clipping test (trivial accept), and new primitives that were created by the clipper as a result of the clipping operation.
- If you render 100 triangles and clipping is enabled and all the triangles are trivially accepted, the Post-Clip Primitives is 100.
- If you render 100 triangles and clipping is enabled and all the triangles are trivially rejected, the Post-Clip Primitives is 0.
- If you render 100 triangles and clipping is enabled and one or more triangles are partially located within the viewing frustum, the Post-Clip Primitive count returns a value which could be more or less than 100 depending on the number of triangles that were clipped. If the value is significantly higher than 100 it means that many triangles where partially clipped, and the clipper created additional triangles.
In most cases you do not have to care about the clipper performance on Intel® HD Graphics 2000/3000 GPUs because these graphic processors implement an efficient clipping algorithm in silicon.
For more information on enabling/disabling hardware clipping read the Microsoft* DirectX* SDK documentation.