Technology

Oh, I'm aware! It just felt funny that the very first consumer dedicated 3D graphics card prove that poster's assumption wrong. In any other case they'd be right. In fact, in those days in 1996, there was the SECOND graphics card that had a 3D processor that DID do 2D graphics too, the Sierra Screamin' 3D (with the Rendition Verite GPU). It was about 2/3ds the cost of the Voodoo 1 (3DFX) even if the Sierra wasn't quite as fast. You'd buy the Sierra because you wanted dedicated 3D but couldn't afford a high end 2D card and the high end 3D card.

And CPUs still do it to this day. Nasty, nasty maths involved in figuring out an optimal combination between lookup table size and refinement calculations because that output can't be approximate, it has to work how IEEE floats are supposed to work. Pure numerology.

Like for instance, monsters and other sprite objects in the original incarnation of the Doom engine have infinite height. So you can't step on top of, or over, any monsters if e.g. you are on a ledge high above them. That's because they're 2D objects, and their vertical position on the screen is largely only cosmetic. This is why you can't run under a Cacodemon, for instance.

"Actors" (monsters, etc.) in Doom do have defined heights, but presumably for speed purposes the engine ignores this except for a small subset of checks, namely for projectile collision and checking whether a monster can enter a sector or if the ceiling height is too low, and for crush damage.

This was rectified in later versions of the Doom engine as well as most source ports. By the time Heretic came out (which is just chock-a-block full of flying enemies and also allows the player to fly with a powerup) monsters no longer had infinite height.

Most notably perspective only gets calculated on the horizontal axis, vertically there is no perspective projection. Playing the OG graphics with mouse gets trippy fast because of that. Doom doesn't use much verticality to hide it. Duke Nukem level design uses it more and it's noticeable but still tolerable. Modern level design with that kind of funk, forget it.

It's embarrassing when a modern game does that. Game Programming 101 now tells you to keep physics and graphics loop timing separate. Engines like Unreal and Godot will do it for you out of the box. I'm pretty sure the SDL tutorials I read circa 2003 told you to do it. AAA developers still doing it on this side of 2008 should be dragged outside and shot for the good of the rest of us.

With resolution 320x240. And I do not remember how many colors. 256?