by the way, there is an amazing code to calculate raytraced quaternion julia sets on the GPU. you need a PS 3.0 card (nvidia 6200 or higher) to get it to run.
i rendered this video in only 2 hours on a nvidia 6800 card: http://vvvv.meso.net/tiki-index.php?page=TonfilmsPatches
a nice detail: http://vvvv.meso.net/tiki-browse_image.php?imageId=1511
and from somebody else a pic: http://vvvv.meso.net/tiki-browse_image.php?imageId=1509
the code can be found here: http://graphics.cs.uiuc.edu/svn/kcrane/web/project_qjulia.html
keep on codin'
tebjan