Thanks V. Truth is, there's nothing to it. I have one infinite light at 75% and the environment sphere, just as TG is doing, rendered in Poser Pro 2010 with IDL and render GC turned on.

In Poser 7 with shader GC and IBL+AO, it's about the same.

In Poser 8, without render GC, things get trickier. Shader GC with IDL is the problem case.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)