"Rune S. Johansen" wrote:
>
> Try to render the little animation below and you will see the Ghost of POV
> effect caused by union and wood normals (name made up by Uwe Zimmermann I
> think). 10-20 frames is enough to get the idea.
>
> I still wonder what actually causes the weird effect.
>
> Can any of the programmers explain it?
>
You mean those three mysterious light/dark spots? That's caused by the
algorithm used to find the surface normal. The algorithm (in the function
Perturb_Normal in the file normal.c for you programmers) uses a pyramid
of points to sample the normal map (here a simple onion pattern) to
determine the surface normal. This locus of points is chosen at a
specific 'radius' around the sample point. The 'radius' of this
pyramid of points is chosen by DELTA which is defined just prior to
Perturb_Normal. By changing the value of DELTA I can make these dark
points move in and out. Getting rid of them is something I do not know
how to do, though. And making DELTA smaller or bigger causes other
problems.
-Nathan
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