2.5D

[665b1ae405263XKILLJOY98]

I watched this video and was curious as to how system shock falls under this (given how it has multi layer levels, 3d objects, etc.)

https://www.youtube.com/watch?v=zb6Eo1D6VW8

Your thoughts?

[665b1ae4054c1Gawain]

Levels are tilemap like wolfenstein with additional height and slope data. Renderer is closer to Quake than Doom (as it renderers polygons/triangles). I don't know exactly how it works, but I think there are specialized optimized rendering code for each tile type and its parts (sloped floors and ceilings, walls divided to sloped and nonsloped sections etc.). It seems there are no special depth or sbuffers used, but simple painters algorithm.  Renderer renders one tile at a time including all objects in it and then moves to next tile.
Because of level data no multilayer levels are possible, but can be faked using 3D objects.
It would be interesting if some of the original developers would have time to explain it in more detail.

[665b1ae4055c4XKILLJOY98]

Interesting, does cyberspace work the same way?

I watched a past live stream the devs had and they did have some neat insight, though I don't ever remember them bringing this up (though I didn't watch the whole live stream/video either). 

[665b1ae405716ZylonBane]

The guy who made that video doesn't understand the subject half as well as he thinks he does.

[665b1ae4057f7Gawain]

Cyberspace most likely has its own renderer for level geometry. Level data is the same.

[665b1ae4059a1chickenhead]

This guy's full o' crap.

A 2.5D game, (Edit) From a design standpoint (Edit) is a game that is fundamentally 2D, but uses 3D graphics and has some 3D features.

A good example of a 2.5D game would be Klonoa on the Playstation.  It's a side scroller platformer, but the levels twist and turn around, and there's even a point where you're on this mine cart thing going forward, and Boss Battle arenas loop around in a circle. But you can only move in two dimensions.

System Shock is a 3D game.  You have full 360-degree movement, you can jump, aim in all directions, etc.

[665b1ae405aa1Gawain]

Doom is a 2.5D game. Doom simulates 3D in many ways without doing 3D calculations.

The usage of term 2.5D is broad, used to describe both technical and gameplay.

[665b1ae405c2fBriareos H]

That does surprise me. I've always seen "2.5D" used for axonometric projections, scrollers with deep parallax and 2D games using sprites pre-rendered in 3D. I mostly remember people putting Doom and all similar games under the "raycaster" moniker (although if I remember correctly Doom isn't actually a ray casting engine).

[665b1ae405d07Gawain]

Ray casting is one of the techniques to fake 3D using 2D data. So 2.5D indeed.

[665b1ae40610fOlfred]

The guy who made that video doesn't understand the subject half as well as he thinks he does.

Exactly what I thought when I saw the video.

[665b1ae40651aRocketMan]

Exactly what I thought when I saw the video.

Please share with the rest of the class? (because I was sufficiently convinced)

[665b1ae40675eZylonBane]

I've always seen "2.5D" used for axonometric projections, scrollers with deep parallax and 2D games using sprites pre-rendered in 3D.

That's what happens when console dummies get ahold of an existing term and reuse it.

Doom was described as a 2.5D game practically from the moment it was released. I've found instances of it in Usenet posts as far back as 1994.

[665b1ae406966voodoo47]

also, isn't pretty much every 3D game just faking it? they all display pixels on our flat, 2D monitors in a way that fools our brains into thinking that there is depth, "stuff behind the screen". why would the way of faking matter?

[665b1ae406af7ZylonBane]

That's taking the term too far. An FPS game is considered "full" 3D if:
1) You can define any arbitrary level geometry and item placement in 3D space, and...
2) The renderer can draw arbitrary 3D geometry.

Doom's internal data structure for representing levels was basically a low-resolution height map, so you couldn't do rooms over rooms or sloped surfaces, and the renderer was specifically only capable of drawing this very constrained type of world, with the player's viewed fixed straight ahead. It could not rotate the view or even allow looking up or down (due to being raycast based). So because the gameplay was kind of halfway between 2D and true 3D, it got called 2.5D.

The original System Shock could also be considered a 2.5D game, because even though the renderer was drawing true texture-mapped 3D polygons and the player could look in any direction, the internal data structure was still just a tile-based height map. At any given X/Y coordinate you get a floor, a ceiling, and maybe a wall. No rooms over rooms.

[665b1ae406f03Al_B]

It could not rotate the view or even allow looking up or down (due to being raycast based).

It's been a while since I played with the sources but I'm pretty sure that Doom wasn't raycast based - at least not in the sense that Wolfenstein was.  The inability to look up or down was to allow fast texture mapping without having to deal with perspective effects within a single texture mapping operation.

I agree with the rest of the post, with the observation that System Shock did allow the player to walk on objects to simulate 3D geometry, similar to Underworld.  Although the base level geometry wasn't 3D this is a distinction that separates it from Doom which had no ability to deal with objects over objects.

[665b1ae40701cZylonBane]

It appears you are correct sir.

[665b1ae407117Al_B]

Good to know that at least one of my 2.5 brain cells are still intact

[665b1ae40738bOlfred]

Please share with the rest of the class? (because I was sufficiently convinced)

He talks about it as if the "Binary Space Partitioning" was what made DOOM not being 3D, but actually it could have been done without it and still not being 3D.
It was merely a means to save memory and computing time. He even said so himself in the video.
At minute 7 he describes the real deal.