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EVSM negative moments

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My current version of EVSM store only positive moments and reduce bleeding quite well but there are still some bleeding problems.

I read there is a way to significantly reduce bleeding with negative wrap but I am not sure how to do it.

Here is what I think should work:
- I wrap moment of negative depth. Well everything bellow 0 got into 0 - 1 range and I am using e^(c*d*-1.0) and bigger the depth is smaller values will be stored => if negative moment is bigger than scene depth, I am in shadow (just reverse to positive moment)
- ok I stored moments into RGBA32F and compute positive and negative Chebyshev bound and use minimum of them

Now I should be able to reduce bleeding but nothing seems to help. If I use only negative moments I got similar looking shadow so I think my computation is correct

Possible problem should by with constant because I am unable to use higher constants (c>5.0) for negative wrap because I don't see almost any part of shadow. I am using c=40 for positive wrap without problem but I am not sure if negative moments are stored correctly.
Maybe I misunderstand something so any help will be welcome.


Values are stored correctly I just use too big max value. Here are pictures from scene (PSSM using EVSM with 3x 1024x1024):

shadow from negative moments:

shadow from positive moments:

As you can see negative moments cover smaller area so final shadow will be same as shadow from positive moments. Maybe z distance difference between objects is too big so bleeding cannot be successfully reduced.

[Edited by - SaTANO on September 1, 2010 3:55:07 AM]

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