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Author Topic: Distance Estimated Soft Shadow Banding Artifact  (Read 2087 times)
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Geometrian
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Posts: 19


« on: May 05, 2013, 06:03:27 PM »

I'm getting banding artifacts in my soft shadow algorithm (functionally the same as that described by http://iquilezles.org/www/articles/rmshadows/rmshadows.htm). Here's a render; notice the banding along shadow edges, especially in the main holes of the L1 sponge:

I don't know what the problem is, although I conjecture it might be because different rays' minimum distance estimates may not actually be the minimum distances of tangency.

I'm sure this problem has been seen before; how is it solved?

Thanks,
-G
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elphinstone
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mattia.gollub
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« Reply #1 on: May 05, 2013, 06:21:59 PM »

Probably you have alread checked it... but are you sure that you are NOT using regular sampling? Usually these artifacts appear when you sample points on a regular grid. Jittered sampling can solve the problem.

EDIT: I don't remember where and in which context, but I read somewhere that making the rays start at different positions can help solving similar problems.

Code:
rayOrigin = viewOrigin + rand(0.0, EPSILON) * rayDirection

I hope this helps smiley
« Last Edit: May 05, 2013, 06:27:16 PM by elphinstone » Logged
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