Does Arnold has a proximal shader? The closest workaround I found was using the camera shader, but that has some limitations.
I used AO recently. But again, limitations.
AFAIK you cannot get the position of another object into the network. You can vertex maps, but this is going to be resolution-dependent.
Thanks! Using AO is a good hint. I also convert shader to vertex map sometimes, but depending on the mesh resolution, the vertex map can slow down the viewport performance dramatically. It seems that the camera shader reads the position and even rotation of a camera. So it should be somehow possible. Hopefully we see a proximal shader in future releases. It can be really helpful in lost of cases.