![Andreas Stromberg](http://mrbluesummers.com/wp-content/uploads/thumbnails/offsite/2663.jpg)
“Indigo is free for commercial and non-commercial use. Employing advanced features such as Metropolis Light Transport, spectral light simulation, a virtual camera model, physical sky and more, Indigo Renderer can achieve much more realistic results than traditional global illumination ray-tracers.”
http://www.cgarena.com/freestuff/tutorials/misc/indigo/indigo-cinema4d.html