That's it! I'm pretty sure I spoke of this before - that playing with IDL revealed to me that much of what we have always thought was SSS is actually bounced light, skin-to-skin. This light is pink. When it lights a nearby skin surface, it makes that area more red. The more it bounces back and forth, the redder it becomes.

That's why I say drop the SSS in VSS with IDL.

Face_off was the one who first told me to make the shadowed areas more red, because SSS is happening there. I believed it, because it looked right. But it wasn't SSS - it was indirect lighting at work! In any case, whatever we call it, the VSS shader is adding some red in the less-lit areas of skin. This is redundant with IDL. In fact, it's more than redundant. It's wrong. If you put a blue t-shirt on the figure, the underarm should be more blue, not red, and it will be with IDL.

Face_off, before he dropped out, was working on using reflection to pick up nearby colors, because he felt that something was missing. Indeed, something was missing, and that was GI. With GI, we don't need the fake redness, or soft reflections, to get that effect.

The fact is that IDL is soft reflections - extremely soft, in a cone of 180 degrees. If we could control that cone a bit, making the angle less than 180, we'd actually get soft specular effects. Sigh.

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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)