Volume lighting tests with mental ray. Found this book very helpful. Its not an easy read (gets very technical) but contains an abundance of condensed knowledge that is difficult to find. If you use a version of Softimage prior to version 2011, download the .spdl files below for the required shaders.
Derek Jenson Blog
My website serves to archive experiments, document projects, share techniques, and motivate further exploration & artistry in 3d space.