its an easy way to fake certain effects, but it doesn’t seem like it works.
Here’s a decent example of different effects that can be faked using it
I just want to make the back/bottom side of a lit object darker. I have the ambient light simulating the (not very strong) blue light that comes from the sky, a yellow/orange main light simulating the sun, but the bottom and the far side of the objects dont end up looking very good.