Here's a couple of links to get you going with kray:
This is one helluva long thread on Newteks forum:
http://vbulletin.newtek.com/showthread. ... 461&page=1
and here's a official site with couple of tutorial files and manual:
http://www.kraytracing.com/index.php?subpage=1
If you find any more please post them...