Here is a wire frame showing one of these crystal ridges.

The scenario is a square cloth falling onto a torus and cylinder. A ball drops from above into the center of the torus, pinching the cloth. This pulls the cloth in a bit over the torus, creating a bunch of ridges on the ground.

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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)