Use Interleaved gradient noise for shadow samples #45326
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akien-mga
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Calinou
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Instead of using white noise for shadowmap lookup, rotate samples with interleaved gradient noise (IGN). IGN is described as being halfway between a dither pattern and noise. It is extremely fast to compute (about half the instructions of our previous noise), and most importantly has very little low frequency properties. This means that it looks more uniformly "random". White noise tends to have "clumping" artifacts making the noise more obvious.
I didn't go with this initially because I was afraid of the obvious dither pattern. But as I read more and use the engine more it is clear that white noise is just not as good.
Comparison image: Top is white noise, bottom is IGN
