YafRay is a powerful raytracer, under the LGPL license. It enables you to
create fantastic images and animations of a photorealistic quality.

YafRay's dependencies are:

libc, libgcc, libstdc++, libjpeg, zlib included in Slackware 12.1. 

scons, libopenexr, and ilmbase available at SlackBuilds.org.