Here is what you see if you look at it from the wrong angle. The tan polygons are facing North. The blue polygons are facing south. That's all there is to it.

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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)