Originally posted by Celshader
…Adrian van der Park developed an excellent technique for this effect back in 1998…
Yeah, I remember that one, I still have the tutorial. Tried to find his webpage but no luck.
These examples are really cool though, thanks for sharing 
EDIT:
I don’t want to bump this thread, but here’s something for new readers to tate a look at… it’s a plugin that supposedly does all of this by using an image. http://www.shift.gr.jp/html/staff/sp/sp000005.html