Sorry I took so long. I discovered many new and weird problems with shader nodes while building this shader. I am pretty satisfied to show it now. But - this is no trivial shader. It is over 100 lines of matmatic and generates 81 nodes. It has 25 important parameters - I could add more but I'll wait on that.

Here's a visual.

Now I have to think about how to explain how it works.

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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)