RhinoMan is a Rhino rendering plug-in that provides a graphical user interface for several RenderMan compliant rendering applications. You can render directly from Rhino without exporting to another application. RenderMan is a modeler-renderer communication standard developed by Pixar which renderer developers can use. Pixar sells its own RenderMan compliant rendering application called Photorealistic Renderman (PrMan). PrMan is the application used to generate all their animated films. PrMan is also used heavily in the movie industry by many other different special effects houses.
There are many RenderMan compliant rendering applications developed by different vendors. Some are free and some are not and all have different capabilities.
RhinoMan currently supports:
1. PrMan - http://www.pixar.com
2. AIR - http://www.sitexgraphics.com (non-free commercial renderer, many great features)
3. 3Delight - http://www.3Delight.com (free commerical renderer, slow global illumination)
4. Aqsis - http://www.aqsis.org (opensource renderer, no raytracing)
5. Pixie - http://sourceforge.net/projects/pixie/
6. RenderDotC- http://www.dotcsw.com/rdc.html (not free, no raytracing)
The big advantage of a RenderMan compliant application is that, inside Rhino, you get access to the same rendering technology used in professional studios. The renderers are also customizable using a programmable shading language if you have that need. A renderer like AIR is inexpensive and you get features like global illumination, caustics, toon shading.
The Rhino 3 version has been available for a couple of years and the Rhino 4 version will be available soon.