This is part of a series of blogs on Embree, a collection of high performance ray tracing kernels. Embree has been released open source since version 1.0. Version 2.0 was released during SIGGRAPH 2013 and Embree 2.1 was published on github just before Christmas 2013. The official web site has an overview on Embree with links to source code and example data sets. I'm not going to duplicate what's already been said over there and in the README.txt.
Photo-realistic rendering requires accurate simulation of light propagation according to physics laws. The best known way to solve this problem is Monte Carlo ray tracing. We describe a state-of-the-art photo-realistic Monte Carlo rendering engine.