Cycles: prevent part of texture from being illuminated (AO, no shine, etc)

Question

I see this requested here and there and people like to lecture about how it "isn't realistic". Solutions that are offered are too niche for my use-case.

I have a throat texture and need part of it to not be illuminated AT ALL. I cannot base this effect off of geometry because the edge flow doesn't match the texture. I need to fake depth for the throat. I am only using a diffuse map and a normal map:

This looks pretty good tbh but that is because his mouth is at a downward angle. Notice that if I create a new BSDF material with a 100% black color and put it on a cube, the problem is obvious:

How can I prevent light from interacting with part of a texture AT ALL?

Answer 1

Ok, so I actually did this before but forgot, and since I don't see this solution anywhere else (until mods come and point it out to me), here is the solution:

Specular.

Create an AO map where the baseline color is "50% gray" (HSV: 0,0,0.5) and the completely occluded areas are 100% black (HSV: 0,0,0). (I make all my grayscale maps "grayscale" color mode but am always disappointed by how little effect that has on file size.) Plug that into the Specular property of your Principled BSDF shader.

Before:

After:

In case that is too subtle...

Before:

After: