This is just a simplistic description of Perlin Noise. However while implementing the algorithm this is not the way to go. Because it's very very slow -- the author has simply taken non-coherent noise and smoothened it and this is computationally very expensive.<p>And also Ken Perlin has made an improved version to his original with some speedups and a reference implementation in Java can be found here: <a href="http://mrl.nyu.edu/~perlin/noise/" rel="nofollow">http://mrl.nyu.edu/~perlin/noise/</a>
I wrote a Python extension based on the original Ken Perlin's algorithm. Just found it on my hard drive and uploaded it to github: <a href="http://github.com/ii/perlin" rel="nofollow">http://github.com/ii/perlin</a>
I've implemented 2D perlin noise for my final year project, but I think it has mistakes in it. Never got the time to verify. If anybody wants to take a look it's here: <a href="http://trac.assembla.com/terrainium/browser/TerrainiumLatest/Terrainium/src/terrainium/AlgorithmPerlin.java" rel="nofollow">http://trac.assembla.com/terrainium/browser/TerrainiumLatest...</a><p>perlinNoise() is the function to look at. I implemented it based on <a href="http://web.archive.org/web/20070706003038/http://www.cs.cmu.edu/~mzucker/code/perlin-noise-math-faq.html" rel="nofollow">http://web.archive.org/web/20070706003038/http://www.cs.cmu....</a> but the images are missing in the web archive :(
Wow, 2 Ken Perlin related posts in an hour! I met Ken Perlin once very briefly and randomly and was a bit in shock when I realized who I was talking to. He was in shock that I was in shock. Nice (and very smart) guy.
If you're interested in noise functions, you might want to check out Pixar's wavelet noise - <a href="http://graphics.pixar.com/library/#WaveletNoise" rel="nofollow">http://graphics.pixar.com/library/#WaveletNoise</a>
A never-released (3d space mmorpg wing-commander-esque) game my friends worked on for a while used this for texturing their worlds: <a href="http://www.cocommand.com/" rel="nofollow">http://www.cocommand.com/</a>