This image from one of the linked threads demonstrates that all values but 0 are actually "outward". This is the magical tile demonstration made real.

And this demonstrates that the offset will shove the whole thing back into neutral position, with only the white and black areas actually moved from original position.

In the latter image, there is, in fact, still a step, because I used .5, not 128/255 (or 127, whichever it should be - I didn't measure it). But it's really small.

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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)