Just found a thread at http://www.renderosity.com/messages.ez?ForumID=12368&Form.ShowMessage=1284637, thanks 'shoop and gebe for the info. seems like it needs some tweaking of params, but might do, else torus /PS images. ta.

Been out of country the past few years (now back in OZ), hope to place some images online in a few days, + working on a web site. Ta.

Thanks mate I appreciate the help, I seemed to recall seeing something a long while back from Gebe, as regards a function?? that would do this but hours of searching still can not find it. Will check out your advice, ta and thanks. Stell.

Found Crossroads, here is the site, thanks to everyone, hope this might help others too. http://home.europa.com/~keithr/Crossroads/index.html and http://www.acm.org/jgt/papers/DinersteinEgbertFlann01/Readme.txt