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Comment by mbel | Hacker News Reader

What do you mean "fake 3d"? They are as 3D as any other computer generated images with linear perspective. Quake is even using a rasterizer like nearly all games today.

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I'd take the benefit of the doubt and consider the poster oblivious to the vast difference between Doom and Quake, they probably just threw them both into the "early 90s 2.5D FPS" bucket.

The word fake doesn’t bother me, but maybe “limited 3d” would be a better term for it. The 3d it had was still correct 3d, sure, it was just limited in what kinds of 3d it could render, unlike the full 3d games that came soon after.

It wasn't really 3D, you couldn't look up or down at all in the original doom I think and in the later games you could, but it got all horribly distorted, as the engine couldn't actually show the scene from different perspective.

Doom used 2D sprites, so "fake 3d" if you ask me.

So does plethora of today's AAA titles for subtle details like particle effects, grass and others.

yes. but sprites (i.e. enemies and weapons) are the primary method of interaction with Doom.

Grass and particle effects are secondary....

How many FPS AAA titles today use sprites for enemies and weapons?

Funnily enough the sprite based enemies were a real strength for Doom compared to many of the fully 3D games that came out in the next generation, including Quake. Because rendering full 3D enemies was taxing for the hardware you couldn't put too many of them on the screen at once. In some games more than 2 or 3 would cause it to chug. So you only ever run across one or two enemies at once in the games, unlike Doom that wasn't afraid to throw a swarm of pinkies at you because you just picked up the chainsaw.

Agreed. I think "Painkiller" is one of the few games that actually managed (much later) to put a healthy amount of enemies against you just like Doom did..

Doesn't matter, to the Doom engine they are tall cubes , albeit with increasingly awful collision detection as the cubes increase in size.

So according to your definition Doom is a full 3d game, even though as a player I actually see 2D weapons and 2d enemies?

Of course it is in the "game" sense. It handles X, Y, and Z axes in game on mobs and the player, although it is selective in which mobs get the "Z treatment". Monsters are infinitely tall, projectiles aren't. It's not a limitation of the engine as much as it was a design choice, as Y-shearing was too ugly in Carmack's opinion, so it was removed in favor of a very forgiving auto-aim.

Nothing's stopping someone from adding code to render 3D models or "portals" in the game, and in fact it has already been done, with no 3D acceleration needed.

The terms "fake 3D" and "2.5D" in reference to Doom and similar games has nothing to do with sprite based mobs, it's about not having a truly 3D map. Doom's maps were drawn in 2D top-down with a height variable for any wall or platform. You couldn't have one room above another, which is why elevators in the game were solid (you couldn't stand under the floor). The various level editors for Doom based games looked like primitive 2D CAD programs.

Quake was a whole new paradigm, it was based on a true 3D engine and its maps were generated in three dimensions. You could stand under stairs, under the room above, and underneath lifts.

It's surely both the sprite-based monsters and the "2.5D" world that justify DOOM's "2.5D/fake 3D" label, though indeed more the latter. (System Shock was a transitional example of sprite monsters in an otherwise full-3D world: https://youtu.be/CGKidgwcalM?list=PLqqLcEJ9bUtNedMdW64WioyV9... )

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