Can anyone help me find how the procedural textures are implemented in the source code? Are the algorithms easy or complicated, so they could be used in own standalone Python-scripts? (Mainly I would be interested as “a case study” of the Cloud-texture.)
You could look at the example texture plugins included with blender.
well, the clouds texture is implemented Blender2.49source\source\blender\render\intern\source exture.c in the clouds() function. How easy or complicated that is depends on how well you read C I guess but it certainly is no case study.
A good book albeit pretty expensive is Texturing and Modeling: A Procedural Approach (The Morgan Kaufmann Series in Computer Graphics)
It is written by the inventors of many of the procedural algorithms now in wide use (like Perlin, Musgrave, etc)
A good web starting points might be:
An easier way is to simply use Mosaic and Aqsis.
That is what Renderman shaders are all about.