It's a bit like a fluid pet scan, each angle will give partial information, you "integrate" to gather the surface.

Gives me ideas.

Think of the intro to the Ghost in the Shell, where the android body is floating up through a bath, and the manufacturer layer on the body is dissolving and being removed. This method could detect that the material is 100% removed from the body as well as confirm that the body is created exactly to spec.

I guess that would be possible, but one has to do some trickery to find false data.

Maybe correlating the exact oposite dip works: Dipping a bowl shows a negative volume then the bowl begins to fill. A dome (reversed bowl) will show additional volume of trapped air at the same point.