The geometry of the map was very simple. An open courtyard with four walls, at one end a doorway into a hexagonal room. I was experimenting with 2D skyboxes and wrapped the entire layout in a hollow brush. I compiled and loaded the map in-game and extra geometry was attached onto all the surfaces of my rooms. It looked like every vertical brush and horizontal brush on the hexagonal room had an extra, equal-size brush attached to one of its faces. I'm still not exactly sure what happened and I just nuked the whole thing and went to bed. I haven't come across anything like that in any forum thread or tutorial. Is something like that possible?