Doom Builder

Doom Builder is an editor for the computer game Doom with support for both vertex and linedef based editing styles. It also allows users to edit light levels, sector heights, and textures in a realtime 3D mode. It features support for many Doom source ports, including ZDoom, Eternity, jDoom, Boom, Skulltag, ZDaemon, and Doom Legacy. It is being developed by Pascal "CodeImp" vd Heiden and is free software, licensed under the terms of the GNU General Public License.