Renders the fog into its own separate texture that can be then upsample on screen. It will contain height fog, volumetric fog as well as local fog volumes contributions. 0: Fog separate composition runs at full resolution, 1: Fog separate composition runs at half resolution.
Usage
r.Fog.SeparateComposition.HalfResolution [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.