Well I did try depth of 100 as I said above.

The Brightness Threshold is something new to me. I think it means don't send another ray out if it is going to be multiplied by a factor that is lower than this number. However, I doubt it applies here, because the brightness in this case of the errent ray is 100% or 1, well above the threshold.

Still I'll try it, but not today - gotta go off to more consulting.

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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)