Hi - just popping in for a minute.

Your questions are valid but it's like wanting to know what each key on a calculator is for. The + key is to add, but you want to know why you would add, or in other words how do you use addition in practice. The answers are, of course, innumerable.

Case in point is your question about the subtract node. You rendered without it to see what happens - nothing. That's because I was anticipating a boundary case that you're not running into at the moment.

If, however, you were to push the bump depth up quite a bit, for whatever reason, you'd start to see artifacts around the folds of the eyelids unless you have the subtract .5 in there. When people use a bump depth of 1 millionth of an inch, it doesn't matter much that mid gray is actually the zero-point, and you're getting two millionths of an inch of bump. However, if you increase the bump 5/100ths of an inch, and then you double it because of the Poser Black=0 phenomenon, well you'd see the problem. Then you'd wonder why my shader doesn't show artifacts and yours does.

I've thought about writing a definitive Poser shader book. I keep vacillating between thinking I can best serve the community with instructions, versus I can best serve the community by just doing the work.

Frankly, I'd love to write the book. Would be cool to be an author.

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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)