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Am 2015-02-11 um 23:56 schrieb Matteo Bruni:
It's probably hard to measure and not going to really matter in practice but toggling the depth clamping (where supported) might be slightly faster than updating the projection matrix.
I'll try to patch my drawprim overhead tester to test this.
I don't expect it to be faster though. At very least it depends on the game's behavior. One of two switches that needs to be toggled to disable depth clipping is switching to POSITIONT vertices, in which case we update the projection matrix anyway.
Even if there's a minor performance advantage of depth clamping in cases where an application constantly uses POSITIONT and switches ZENABLE on an off I prefer to always use the projection matrix to have only one codepath that does this. If there's a huge difference we may think about two alternating codepaths.