Fast mobile shaders or rather Mobile! Fast!

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Hidden Surface Removal• Deferred• bins all primitives into tiles (~16x16 pixels)• uses micro Z-buffer to reject hidden fragments• gathers visible fragments and sends for rasterization•Early Z-cull• coarse Z-buffer: low-resolution, low-precision• if fragment fail Z-test it will not be sent forrasterization• sort opaque front to back, GPU will not rearrangepolygons for youTBDR: while rendering a tile, a lot of relevant data is kept in fast on-chip memory.Additionally, visible fragments are found by the hardware and pixel shaders (andconsequently all texture fetches) are ran only on them.Others (Tiled & Classic) use “early z-cull” or similar schemes to help reject some of thehidden pixels.
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).
Page 1 and 2: Fast mobile shadersor ratherMobile!
Page 3 and 4: Outline• Desktop vs. Mobile• GP
Page 5 and 6: Mobile•••Needs to use 100x le
Page 7 and 8: Old Is New•Techniques from 2001 i
Page 9 and 10: Workload••Frequency of computat
Page 11 and 12: Scene•••Opaque is the bestAvo
Page 13 and 14: “Onload” CPU?••More fast co
Page 15 and 16: GPU Species••••ImgTec Power
Page 17: Architectures•Tiled Deferred• P
Page 21 and 22: Hidden Surface Removal•Simple geo
Page 23 and 24: Saving BW & ALU•Framebuffer write
Page 25 and 26: Tiled Framebuffers•Higher Z preci
Page 27 and 28: Case: MSAA•4xMSAA, iPad2• 6ms i
Page 29 and 30: Case: Mipmaps•••Turn off mipm
Page 31 and 32: Case: OptimizingSHADOWGUN forTegra
Page 33 and 34: SHADOWGUN+Tegra2••Target 30 FPS
Page 35 and 36: Sort opaque geometry!•Saved ~15ms
Page 37 and 38: LUT Baking ToolsAnother bonus: sinc
Page 39 and 40: Texture Compression•••Tegra h
Page 41 and 42: Profiling toolsTools
Page 43 and 44: PVRUniSCoPVRUniSCo gives cycles for
Page 45 and 46: PerfHUD ES
Page 47 and 48: Tools: Android + Adreno•Adreno Pr
Page 49 and 50: Shader Performance
Page 51 and 52: GLSL ES specific•Precision qualif
Page 53 and 54: General Intuition•••Note: Han
Page 55 and 56: Precision: half / mediump••16 b
Page 57 and 58: Precision•Minimize conversion bet
Page 59 and 60: Shader Performance•Some shaders
Page 61 and 62: Shader Performance••Normalized
Page 63 and 64: Relative Performance•All lines in
Page 65 and 66: Unannouced TitleHigh poly, lots of
Page 67 and 68: Current state••37FPS after opti
Page 69 and 70:
Getting GPU time on iOS•Force CPU
Page 71 and 72:
Post-processing•Precision: lowp/f
Page 73 and 74:
Burning Walls shader
Page 75 and 76:
Burning Walls shader•Saved ~8ms p
Page 77 and 78:
Optimize Particles•Reduce overdra
Page 79 and 80:
Case: AngryBots
Page 81 and 82:
AngryBots••Not much optimizatio
Page 83 and 84:
Added for PC•••Depth of Field
Page 85 and 86:
Wet floor•Render subset of scene
Page 87 and 88:
Planar reflection
Page 89 and 90:
Albedo
Page 91 and 92:
Gloss (A of albedo tex)
Page 93 and 94:
Pixel shader
Page 95 and 96:
Splashes: geom + atlasWater splashe
Page 97 and 98:
Post-fx costs••At native device
Page 99 and 100:
Combine post-fx•Color Correction
Page 101 and 102:
Cheat a bit•Scratch texture on no
Page 103 and 104:
FXAA•Fast Approximate AA• Post
Page 105 and 106:
Fail #1•FXAA is all float/highp
Page 107 and 108:
Win #1•Use more (5) vec2 varyings
Page 109 and 110:
FXAA 3.11•Latest FXAA 3.1 “cons
Page 111 and 112:
Optimizing FXAA 3.11•Down to 12.7
Page 113 and 114:
Extra SlidesExtra stuff we had init
Page 115 and 116:
“Proper way”•Bake a bunch of
Page 117 and 118:
Actually reflectedThis is what is a
Page 119 and 120:
Ta-da!
Page 121 and 122:
Reflection UVs••Not much physic
Page 123 and 124:
Without Bloom
Page 125 and 126:
Also Color Adj•Can also do simple
Page 127 and 128:
“Mood Boxes” in Unity 3.4 Angry
Page 129:
Mood Boxes•When entering new mood
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Fast mobile shaders or rather Mobile! Fast!

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