Okay, this is a long shot but is there a thing that would let me do this?
Let me select a POV, and two objects, which I’ll call the Background object and the Target object. Then I can generate UVs for the Target object to match the Background object from the POV.
So if my background object had a big picture of a forest and I wanted the target object to show a specific tree, I could position a target object between the background and the POV and project UVs onto it like that.
There is a UV project modifier, but that just bases it on the POV, so I’d need the texture to match the POV.
I’m not sure if this is helpful at all for your purposes, but I made a pyramid mapping nodegroup. Follow the outputted coords and mask. I use this for projectors, unfortunately I always need to redo it (mess around with it, new mask, aspect control etc) when I use it since we use lens shift and this one only supports center optics lenses. Ignore the rest of the coordinate transforms (I crossed them out).
Inputs needed are object coordinates (linked empty, z direction is projection direction) and the angle of the pyramid in degrees. As a workaround for aspect, you can stretch your image square and then scale the empty in one axis - I think - maybe… But lens shift isn’t trivial this way. In retrospect, I probably should have made this in a completely different fashion.
Just an example of the kind of stuff you can do with it: