Back Patch Culling
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Figure 14-1 shows the same geometry before and after back patch culling.
Figure 14-1 Before and After Back Patch Culling
Back Patch Culling Advantage
Back patch culling occurs before the primitives are processed by the graphics pipeline.
As a result, back patch culling off-loads some of the graphics pipeline work to the CPU,
yielding an added degree of parallelism between the two processors.
In back face culling, all of the triangles in a geometry are processed and then those on one
side of a geometry are discarded. The amount of processing can be significant, including
1. Sending vertex data across the bus.
2. Transforming the vertices from object coordinates to clip coordinates.
3. Clipping to the viewing frustum.
Not displaying back faces is only a small part of the face processing. Consequently,
culling back faces may not significantly enhance application performance.
In back patch culling, all primitives seen only on one side of a geometry are culled before
their triangles are processed by the graphics pipeline. Back patch culling often improves
application performance by not performing unnecessary processing.
