Is there a "thickness" node? I'm looking for a node that will return a white value for the thickest part of an object (as seen from the camera), fading off to black as the thickness becomes 0. Does such a thing exist?

I'd like to simulate an opaque light without needing caustics, so my idea is that center of the object would be the brightest part with the outer edge being darker.
Is Vector Math set to Length close to what you need?
You can invert it (or not) with a Map Range node, and then the From Max parameter becomes a slider for you to control where the effect terminates.


Something I cooked up using this: