Text Mode Doom

Text mode renderers are a feature which open source hackers find bizarrely novel to incorporate for applications which would traditionally be best suited to a more detailed interactive display. Doom is no exception, and there have been a number of attempts to develop a text mode renderer for it.

SMMU
The SMMU source port incorporated a DOS text-based renderer.

libcaca
Libcaca is a text-rendering library that can be plugged into a variety of other programs and renderers, including libSDL. Doom was used as a demonstration of the library's novelty. The second image below is from Doom Legacy while the first image may also be from Doom Legacy but there is not enough information in the screenshot to determine if it is.

 Installing libcaca and Chocolate Doom on Debian/Ubuntu:  sudo apt-get install libcaca0 chocolate-doom doom-wad-shareware  Running:  SDL_VIDEODRIVER=caca chocolate-doom