An interesting idea from “Aversion of Reality” in the Blender crowd…
“What if we just faked all our face shading?”
What he means is not that you have 12 MATs for the same figure, each with a shadow position directly imprinted onto the skin MAT or some overlay for it. But rather that the scene has flat lighting, and that a module in the skin-shader controls how the skin appears to take a shadow from a light…
… but really the light has nothing to do with casting the shadow. It’s a sort of dynamic pseudo-shadow ramping in the shader.
Nice idea, but could become a bit tangly to co-ordinate across a whole head and shoulders render… unless you then had a master controller for shadows on all hair / neck / jacket surfaces, not just the face skin. But I guess that’s possible, and he already has it working here on both face and neck, as you can see.
You can already do something like this with duo-tone and colour-ramped materials and suchlike, and there are a number of such packs for Poser and DAZ. But what he’s suggesting for Blender shaders is different than that.