In fact, depending on the contour, that may be too much.

Here's a little demo. I grabbed a lip mask I have from the Antonia project and tossed it onto a couple one-sided squares.

The lower one is using the shader shown. The 100x factor makes the visible color transition very sharp, but also makes it start a little bit early, when the displacement still hasn't kicked in.

Next I'll show you how you might adjust that.

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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)