So here is my take on pbr bake, i've modified eetu's scene, moved lense prebake to cops. By the way i think the reason it was inverted was due to camera space(?), P and N results are different in COPs.
It should also be possible to at least semi automate delta offset, but i'm holding the scene for too long already
P.S. eetu thanks for the lens shader, finally got it figured out, sort of
P.P.S. sebkaine, any luck with volumes?
pbr_bake_v011.hip