Sorry again for these multiple posts. I an only trying to give as much info about Embree as I can. This is verbatim from Intel's web site:

Quote - Embree is a collection of high-performance ray tracing kernels, developed at Intel Labs. The kernels are optimized for photo-realistic rendering on the latest Intel® processors with support for the SSE and AVX instruction sets. In addition to the ray tracing kernels, Embree provides an example photo-realistic rendering engine. Embree is designed for Monte Carlo ray tracing algorithms, where the vast majority of rays are incoherent. The specific single-ray traversal kernels in Embree provide the best performance in this scenario and they are very easy to integrate into existing applications.

http://software.intel.com/en-us/articles/embree-photo-realistic-ray-tracing-kernels