Quote - I also have a silly question.  Since nylon is stretchy, shouldn't the fiber density be greater in areas where the material is stretching less (leg parts with lower diameter) and lower in areas it is stretching more?

 
Indeed, but trying to figure that out in a shader is difficult at best, and close to not possible in Poser nodes.

If you really want to get to that level of accuracy, I'd probably just use a gray-scale map, drawing where the fibers are stretched or compressed, and use that to modulate the density value.

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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)