storm_veil

The inside of a cloud, applied to the whole frame. Height fog describes the medium in front of a surface and leaves sky pixels alone, which is right almost everywhere and wrong in exactly one place: inside the deck, where a whiteout on the geometry over an unfogged sky reads as a white tower cut out of a dark sky. This pass closes that gap. It reads the scene depth, gives sky pixels the veil in full and drawn surfaces a share of it, and returns immediately on a uniform when the amount is zero — so it costs nothing for the ninety percent of the climb that is not inside a cloud.