Photon mapping is a global illumination algorithm.  It calculates rays of light from a light source in the scene until some termination objective is met, producing a radiance value.  It's faster than some other methods of GI, and useful for some special effects like realistic caustics and SSS.  Unlike some other methods, it's a biased method of calculation, meaning it uses an "average" equation to produce a rendering or lighting solution.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.