Runtime directory structure
From Doomsday Wiki
This article describes the directory hierarchy as it appears to the engine at runtime.
bin/ data/ <game-name>/ auto/ # Special auto-load folder detailtextures/ flats/ lightmaps/ models/ music/ sfx/ textures/ patches/ defs/ <game-name>/ auto/ # Special auto-load folder run/ # set with -userdir
Note: Most of this structure is configurable with command line options (such as -texdir).