BSP2MAP is a decompiler for GoldSrc maps written by Skyler 'Zipster' York. It converts the BSP files into .MAP format, which can then be loaded into Hammer Editor. Unfortunately, Goldsource maps do not store enough information for brushwork, so the geometry has to be recreated using the polygons. BSP2MAP hollows out all brush-based entities with a thickness of one unit as a preventive measure to stealing/copying maps.
Top: BSP2MAP's attempt to decompile HL crossfire.
Bottom: WinBSPC's attempt to decompile HL crossfire.