we need mix z_dept or mist to 3d viewport real time as fog.

blender volume fog is weird color (not soo pure ) and flicker frequently .

maybe we can mix the z_dept or mist to 3d viewport realtime and able to change color mix mode like adding , multiply .

and in final render we can separate this render pass .

This way is usually being used in game engine as atmosphere fog or mix y_dept as hight fog

we have hoped this feature of a long time since 2.79 .

i try it base on material. but too complex to setup an complex scene. and lake y_dept output node.