For comparison, here is what you get if you use my PR3 shader with built-in AO and skip the light-based AO. It's much more realistic, IMO.

I had hoped that the light-based AO would take care of the fact that only about half the light is ambient, while the other half is from a single infinite at 50%. It didn't. Making the shadowed areas go to black is very bad. My material-based AO is working the way I want it to.

I guess I'll stick with material AO after all.

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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)