In article <3d22036d@news.povray.org>,
 "Klaus Lehtonen" <leh### [at] hotmailcom> wrote:

> Is the interpolation cubic like in sp_lines or cosine based? (
> http://freespace.virgin.net/hugo.elias/models/m_perlin.htm has decription of
> the funtions that I'm writing) I tried to look at the source myself but my C
> skills are pretty bad. If it is cosine based the grid could be natural part
> of the function. I'm thinking this because the small lines that cause the
> grid are visible even when using one dimentional version of the function.
> (just change f_noise3d(x,y,z) to f_noise3d(x,0,0) ) Sorry if this is too
> newbie question for advanced-users.

If I remember correctly, that page describes a very different algorithm 
than what is usually called "Perlin noise". It uses a bitmap filled with 
random values and then interpolated to get the basic noise, which is a 
very simple and direct way of doing it but doesn't give great results. 
The algorithm Ken Perlin came up with was quite different and more 
complex, I don't understand all of it and can't explain it here, but it 
doesn't rely on a 2D or 3D bitmap.

http://www.mrl.nyu.edu/~perlin/doc/oscar.html
http://students.vassar.edu/mazucker/code/perlin-noise-math-faq.html
http://www.threedgraphics.com/texsynth/

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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