Clyde, there is a way to make fog patchy. Do not use Atmosphere settings, but use stones or lattices with volumetric cloud textures. Position them where you want. Adjust density to taste. Take care that the stones do not overlap because you will get weird effects. Voila. Madmax, Inspiration is kinda cheating. Yes, it looks very good, but being black and white, it masks things that would be visible in colour.

-- erlik