Quote - does Firefly IDL use any kind of photons or pathtracing?  or is it raytrace based?

i've never set raytrace bounces over 4.

Unless Poser Firefly reinvented the wheel in the past few upgrades, the raytrace bounces setting, as in almost every raytrace render engine, will affect the raytrace materials used in the scene and how their properties are handled.  Like reflections and refractions, which in turn may indirectly impact how light is transported through the scene by photons or path tracing.  4 to 6 bounces is a pretty common integer in most raytrace render engines.  Much more than 6 or 8 can be overkill, depending on the scene and materials.

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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.