Heheh. You somehow mis-read what I said.

I did not say "That's not possible to exactly position". I said "That's not easy to exactly position".

Suppose I want a circle of radius .275 centered on U = .595 and V = .7818?

In matmatic, I say:

dot = Sqrt((U - .595) ** 2 + (V - .7818) ** 2) <= .275

I can now use that dot to control anything I want.

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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)