I read a long time ago about people running Quake in text-mode. I found the idea really nice,but the screenshots were not all that impressive from my point of view. I decided to write an engine that would do a better job.I was quite pleased with the results, though the program was a bit too slow for real-time at least on the computers of that age (read 486).
Unfortunately this was written during High-School when I was still coding in Pascal for DOS, which makes it really hard now to use it for anything. The input image size is hard-coded to 320x200 with a 256 color palette.
Nevertheless, if it happens to be interesting for anyone, I have attached the sources here.