Sorry I'm taking so long. There are a couple small issues I have to work out yet. There are problems with IDL and with AO. I worry that some people who don't follow all this will not understand why this new eye is so complicated to work with. Answer: Realism requires refraction, and refraction requires hackery.

Also, in preview, with the refractive cover shader, the eyes are totally black. Ooooooooo. People won't like that.

Here's a demo of procedural masking of the iris, and procedurally changing its color, as if we were using a second image.

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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)