Here’s another oldie. This one is a 2.5D, Doom style renderer. It does simple lighting and texture mapping with limited up/down head motion. This is inspired by Doom and the consequent Star Wars games that allowed up/down head motion.
For this, I had to write my own BSP creator which read the level from a text file (2.5D polygonal description). Implementation is fairly low level (x86 - this was meant to run at a descent frame rate on 386 computers. No floating point is used.).
Unfortunately, I was not able to find my source code, but here’s the Windows binary.