SmallUPBP : A (not too) small physically based volumetric renderer

• http://www.smallupbp.com/

Reference

• "Unifying points, beams, and paths in volumetric light transport simulation" Jaroslav Křivánek, Iliyan Georgiev, Toshiya Hachisuka, Petr Vévoda, Martin Šik, Derek Nowrouzezahrai, and Wojciech Jarosz. SIGGRAPH 2014
  • http://cgg.mff.cuni.cz/~jaroslav/papers/2014-upbp/index.htm