In article <41FC85EB.F2421F3A@arkady.demon.co.uk>,
 Bernard Hatt <bmh### [at] arkadydemoncouk> wrote:

> Thanks for the info, looking at the discussion and the code it is
> quite a complex problem...

There are two similar problems. One is a discontinuity in the second 
derivative of the noise function at points on the lattice...this one is 
fixed, as far as I know. The second problem is more fundamental, a 
lattice of points with values near 0.5 (maybe not exact, due to the way 
POV transforms the output range of the noise function)...all POV-Ray's 
noise generators have this problem, and it is not "fixable".


> I can't help feeling there must be an algorithm which doesn't suffer
> from these problems, I might have a play around and see if I can
> find one..

There are algorithms that don't suffer from the lattice artifact. I've 
been polishing up a patch that implements one of them, the Lewis sparse 
convolution noise algorithm. However, there is a tradeoff in speed.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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