Quote - theory: if orthogonal joins are micropolygonal and/or microbeveled, then it would work better.  possibly related problem with poser cone (P7 or P8), which was solved by replacing tip (apex) with tiny empty polygon.  it still looked like sharp point, but eliminated rendering artifacts.

Hmmm. Has anyone tried increasing the subdivision surface density of the geometry, in areas with concave angles and coincident faces?  Looks like most of the images posted so far are very simple geometrically, which you would expect to render good results, but might actually create problems.  Higher resolution geometry might force the raycaster to increase sampling in areas with concave angles and coplanar faces, improving the IDL solution.  Then again, it might worsen the problem, at the cost of even more render time.

I'm just curious if it would make a difference (for better or worse) or at all.  Instead of walls and floors that consist of 2x2 or 4x4 polygons, try geometry that's subdivided to 32x32 or 64x64 at least, and chamfer or bevel the corners of the walls, allowing more geometry in those tight areas to force more sampling.

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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.