Hi,
I have tried the version 1.6 and this is a very good render engine. The only problem is that the doc is a little poor. But with the v1.7 the doc is about to be rewrite.
You can try the demo version 1.6. You can download here :
www.kraytracing.com
This is a full time unlimited version. The only little little little limitation is that it appear a very fine black strip with the rendering time to the bottom of pic.
Enjoy
