Kent did that on the Spice Vendor house collab. He used a node and did some fancy noodling so that objects that were further out from the camera started to look foggy. As a hack to simulate morning due or something. I can’t remember in which of the livestreams he sets it up, for sure it’s after all the modeling, in the shading stages, but it’s there. Also if you download the files and go into the tree’s objects you’ll probably see the setup in the nodes.
https://cgcookie.com/playlists/156-collab-02-2021
