These (lodev and permadi tutorials) were indispensible to me when I was working on my game engine, which used delta force style raycast terrain -- there are extremely few resources on that concept, sadly. Fortunately for us all, archive.org exists to preserve the few articles from the 90s on the subject.
Yes, it's amazing how many game development techniques appeared and faded out in the 90s, in that window of time between fast-enough CPUs and affordable GPUs. I have a copy of the Black Art of 3D Game Programming on my shelf and it's full of awesome tidbits.
I recently browsed flipcode.com and sadly parts of it are broken and only available thanks to the Internet Archive.
While I can still reply to this post I thought I would just mention that of these 3 resources, permadi, lodev, and flipcode, www.flipcode.com was the most important for understanding how to do heightmap terrain in a raycaster, like how Comanche and Delta Force did it.
Those are just for understanding, to go deeper, into code, perhaps the most important thing I found was here:
if anything is broken I believe archive.org has copies of the zip files as well, not just the html.
Just wanted to stick it here so perhaps someone else will find it easier to find, it took me a lot of googling and wandering through abandoned forums, looking for out-of-print books that no one has bothered to digitize, etc.
Why do all these great retro game dev articles get posted this time of year? Don't you guys know I have real side projects to work on. I get caught in an endless dive, peeling back layers of abstraction. This is exactly what got me hooked on development in the first place. I love it.
I absolutely love this tutorial. I followed it many years ago to create a simple raycaster, then extended it to have a ton of features like reflections, sprites, variable height walls etc.
Also check out this other nice raycasting tutorial: http://lodev.org/cgtutor/raycasting.html