Implement faster getWorldPos#52
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* All non-crazy camera projection matrices (excluding ortho) have several zero values. Using a fully generic mat4 x vec4 matrix multiplication wastes work for these zero entries. These big matrix multiplies add up to significant overhead, and N8AO uses this `getWorldPos` function in several places, so it ends up getting called multiple times per pixel per frame. It's actually a hotspot in several N8AO shaders, which I've verified directly myself: https://i.ameo.link/dqf.png * By replacing the generic mat4 x vec4 with a hand-rolled set of FMAs on pairs of non-zero entries only, the total FLOPs get cut significantly while producing identical results * For reference, see: https://www.derschmale.com/2014/03/19/reconstructing-positions-from-the-depth-buffer-pt-2-perspective-and-orthographic-general-case/
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getWorldPosfunction in several places, so it ends up getting called multiple times per pixel per frame. It's actually a hotspot in several N8AO shaders, which I've verified directly myself: https://i.ameo.link/dqf.pngThe only situation I could see this change being a problem is for users with fully-custom camera matrices, like if they're implementing some kind of wonky distortion or mirroring effect or something like that.