Crossbones+ - Reputation: 2918
Posted 19 October 2012 - 06:17 AM
Clip may save pixels from being written to the screen buffer, but on the other hand, it may have detrimental effect on the z-buffering optimizations. So, if you absolutely need clip, call it as early as possible in the pixel shader.
Crossbones+ - Reputation: 7527
Posted 19 October 2012 - 12:26 PM
This blog post has some good information on the topic: http://fgiesen.wordpress.com/2011/07/08/a-trip-through-the-graphics-pipeline-2011-part-7/
If you have no overlapping geometry in your draw call, then it might improve performance.