Hi guys, I was told to post here as you might be interested.
I've spent the last few months writing a full game engine which can also run DOOM. I started out with a clean slate, haven't ever peeked at the original source code, and have come pretty far I think.
I'm doing it to test my software development mettle and because it's simply been quite fun and I've learned a lot about OpenGL, C++, and general game engine development!
I'm also working on an extensive set of tutorials about pretty much everything that has gone into the engine from level and media loading, BSP stuff, audio, physics, and engine architecture, etc.
Here's the link to my twitter documenting my progress and then a link to my site where I'll be publishing the tutorials:
https://www.twitter.com/DOOMReboot
http://www.movax13h.com