This video shows you how to use atmosphere_volume to create a foggy city scene.
Free Kitbash3D scene:
https://kitbash3d.com/products/mini-k...
Arnold user-guide:
https://help.autodesk.com/view/ARNOL/...
https://help.autodesk.com/view/ARNOL/...
https://help.autodesk.com/view/ARNOL/...