Fast mobile shaders or rather Mobile! Fast!

Case: HSR Performance•0.8-3.5ms to reject 1280x600fragments on Tegra2• can reject 2x2 pixels per cycle• real scene: rejecting skybox in SHADOWGUN• 0.9ms•0.05-0.13ms to reject 1024x768fragments on iPad2• can reject 32 pixels per cycle• 0.05ms coplanar geometry• 0.11-0.13ms rejecting arbitrary geometryIf we render a screen worth of pixels that are fully occluded by things rendered before, inboth TBDR and Early-Z it still takes GPU time to process them (much less time than it wouldtake to fully shade them of course).In iPad2 vs. Tegra2 case (NOTE: these GPUs are not equivalent in performance in general), wecan see that iPad2 (PowerVR SGX, TBDR architecture) takes way less time to reject hiddenpixels than Tegra2 (Classic architecture).