In a presentation at the Siggraph 2017 conference, Kohei Ishiyama and Giliam de Carpentier talked about the new system behind the game’s fog.
The developers state that the team had created a new fog system in the Decima Engine that allows for more artistic flexibility over the appearance of atmosphere in-game. Guerrilla Games and Kojima Productions combined the precomputed atmospheric scattering model and an “analytic height fog” model to mix both photorealism and artistic flexibility in a singe model.
The talk, for example, also breaks down the aspects of spherical area lighting: