I'm trying to avoid making my skyboxes one big box (no not a hollowed-out cube brush, i do the separate brush method) surrounding the stage, and instead wish to do them the way Valve typically does it. That is to say, a skybox that is built only as far as the outdoor areas extend, with holes in the skybox geometry to allow for buildings. I am guessing this is done to cut down on render times and memory usage. The problem is I don't quite understand how this works without causing a map leak. Any help or explanation would be appreciated.