What the heck is poser using to calculate shading, though?

The displacement map. That's la femme's UV template. La Femme (pro, which shouldn't matter). units=meters, displacement .1

subd=0

subd=3

The mesh is smoother (of course). but the shadow. It does not relate to the geometry, as rendered. Which gets back (I think) to the origin of this thread. Micro-displacement aside, the shadow seems wrong.

The lighting is superfly studio 3 (a bunch of spots). Maybe should be mesh lights?