I haven't done it for a while on this subject, but a forum search (keywords - 'Raytrace Shadow artifacts' etc) would usually throw something up.
The problem tends to change slightly as versions change - when AO was introduced there were a whole new swathe of problems. The core issue of shadow bias is common to most 3d apps though, from what I know.
3d just is a tricky beast, even using the simplest of features.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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