Game Theorists "Doom Wasn't 3D" video and my refutation

[Orchid87]

1 hour ago, Azuris said:

 

Even if many will not see it, Doom has very much in Common with Super Mario.
It is easier to spot the Differences: The Perspective as the biggest one, Theme, Ability to Jump, more Weapons (but more Health).
 

 

It's a wasted potential that Doom Classic didn't come with an integrated easy to use map editor with share function on consoles. We could have our own Mario Maker.

[Azuris]

1 hour ago, Orchid87 said:

It's a wasted potential that Doom Classic didn't come with an integrated easy to use map editor with share function on consoles. We could have our own Mario Maker.

 

Yeah, but it is ok.
Mario Maker just showed me how many People have no Feeling about how to make enjoyable Levels^^

[magicsofa]

On 12/21/2020 at 10:12 AM, Dark Pulse said:

Well yeah; as I pointed out, projectiles can most certainly pass above and below you. But it definitely impacts player-monster collision; even in Vanilla Doom you can't walk "under" a floating Cacodemon/Pain Elemental/Lost Soul.

 

Okay but why is collision behaving that way? Is it because the collision code says so, or because there's only half of a dimension available?

[Cacodemon345]

2 hours ago, magicsofa said:

 

Okay but why is collision behaving that way? Is it because the collision code says so, or because there's only half of a dimension available?

It's because the z-height check was only done for projectiles. id also didn't implement the code for walking over actors so they had to make it infinite height for non-projectiles.

[Blzut3]

6 hours ago, magicsofa said:

Okay but why is collision behaving that way? Is it because the collision code says so, or because there's only half of a dimension available?

Heretic, Hexen, and Strife all implement solid actor passing.  To be honest, I have no idea why id didn't implement it in Doom.  Not having solid actors cross makes things a little simpler, but not by a particularly significant amount.  Off hand I think pretty much the only thing you have to do is make sure that upward movement can't happen if there's an actor in the way.  Maybe fix some potential division by zero.

[Doomkid]

7 hours ago, Cacodemon345 said:

It's because the z-height check was only done for projectiles.

Nope, it's done for collectible items as well, not to mention z-height checking is also done to determine when a player hits their head on the roof or lands their feet on the floor.

[magicsofa]

20 hours ago, Cacodemon345 said:

It's because the z-height check was only done for projectiles. id also didn't implement the code for walking over actors so they had to make it infinite height for non-projectiles.

 

16 hours ago, Blzut3 said:

Heretic, Hexen, and Strife all implement solid actor passing.  To be honest, I have no idea why id didn't implement it in Doom.  Not having solid actors cross makes things a little simpler, but not by a particularly significant amount.  Off hand I think pretty much the only thing you have to do is make sure that upward movement can't happen if there's an actor in the way.  Maybe fix some potential division by zero.

Sorry, I was asking the question to @Dark Pulse in sort of a rhetorical way. I'm familiar with the mechanics of actors bumping. My question was to say, there must be a source for those behaviors, and that source should be the objective of this discussion. That's why I'm bothered by the term "2.5D". It implies that the source of the specific behavior, Actors-Bump-At-Ridiculous-Heights, which shall now be referred to in short as ABARH, is the lack of a full third dimension. It is, as most arguments, a semantic argument. Everyone agrees that there's z movement at least some of the time. What we don't agree on is whether it should be called 2.5D or not. I say not, because it sounds impossible to have "half a dimension." It leads people to mistakenly believe that the z axis is somehow deprecated, when in fact the mechanics of the projection are the source for the limitation.

Unfortunately for me, the Wikipedia article seems pretty comfortable with saying 2.5D. They also say "pseudo-3D" interchangeably, which I think is a better term. By their description, Doom would totally be called 2.5D:
 

Quote

The reason for using pseudo-3D instead of "real" 3D computer graphics is that the system that has to simulate a 3D-looking graphic is not powerful enough to handle the calculation-intensive routines of 3D computer graphics, yet is capable of using tricks of modifying 2D graphics like bitmaps. One of these tricks is to stretch a bitmap more and more, therefore making it larger with each step, as to give the effect of an object coming closer and closer towards the player.

 

Dimensions are the variables of the data and can be mapped to specific locations in space; 2D data can be given 3D volume by adding a value to the x, y, or z plane. "Assigning height to 2D regions of a topographic map" associating every 2D location with a height/elevation value creates a 2.5D projection; this is not considered a "true 3D representation", however is used like 3D visual representation to "simplify visual processing of imagery and the resulting spatial cognition".

 

The thing is, this would allow even a game like Diablo I into the same category, which only uses 3/4 perspective in the artwork and the ability to go "behind" walls to make it look 3d. To me, that's a better candidate for a term like 2.5D... but even then, should it be called half of a dimension? The only sort of z-level consideration is the order of sprite layering... otherwise, all objects and map elements utilize only x and y coordinates. The layering only changes when an object changes it's y position. That's a much more severely limited usage, so much that I don't want to call it a dimension at all. It's just a layering trick, and it's as two dimensional as the graphic style. They are drawn to appear 3D, but they never change perspective.

Doom, on the other hand, falls into the "assigning height to 2d regions" category. Argh, Wikipedia, argh! I still hate 2.5D because I think it's mathematically irresponsible. Doom objects have a z-coordinate, therefore 3D. Diablo do not - 2D. Wolfenstein.... um....

[wallabra]

On 12/26/2020 at 9:42 AM, Orchid87 said:

It's a wasted potential that Doom Classic didn't come with an integrated easy to use map editor with share function on consoles. We could have our own Mario Maker.

 

"Buh you can't snapmap with... linedefs and sectors! And bee-ass-pee!"

[Dark Pulse]

2 hours ago, magicsofa said:

The thing is, this would allow even a game like Diablo I into the same category, which only uses 3/4 perspective in the artwork and the ability to go "behind" walls to make it look 3d. To me, that's a better candidate for a term like 2.5D... but even then, should it be called half of a dimension? The only sort of z-level consideration is the order of sprite layering... otherwise, all objects and map elements utilize only x and y coordinates. The layering only changes when an object changes it's y position. That's a much more severely limited usage, so much that I don't want to call it a dimension at all. It's just a layering trick, and it's as two dimensional as the graphic style. They are drawn to appear 3D, but they never change perspective.

Diablo 1 and 2 are 2D. You only move in two axes fundamentally. You never go "up" in terms of the game world, the maps are on a perfectly level field; there's no stairs or height changes or anything like that.

 

The perspective tries to give an illusion of 3D, but fundamentally for three dimensions you need an X, Y, and Z axis. Doom has all three, some just can't make use of its Z-Axis in certain circumstances. But in Diablo, you're never going on whatever axis would be the "up-down" one - just the forward-backward and side-side ones. Diablo 2 enriches it to ordinal directional movement and at least begins faking height via suggestive graphics, but you are not ACTUALLY moving up and down, and still are limited to two sets of axes.

 

In Doom, however, you CAN move in all three directions. So there is a definite third dimension to the game in some respects. But since you can't do it in ALL respects, and indeed cannot do things such as looking straight up or down, fundamentally the game is limited by its rendering and worldspace representation, and cannot accurately reproduce true 3D effects.

 

Hence, it's not quite a pure 2D engine, but neither is it quite a pure 3D engine. It's somewhere in the middle. And thus the term 2.5D was born, because it's fitting - you've got two full dimensions, and a partial third one that is fully implemented in some respects, but not in others.

Edited December 27, 2020 by Dark Pulse

[Blzut3]

1 hour ago, magicsofa said:

I still hate 2.5D because I think it's mathematically irresponsible.

Mostly because I felt like writing this.  I understand that you probably agree with at least some of the following since you say "when in fact the mechanics of the projection are the source for the limitation."

 

Personally I find the term "2.5D" to be just fine if you're not trying to force the literal string "2.5D First Person Shooter" to be a mathematical concept just because it happens to look like "3D" and instead just interpret it as a descriptor for a certain type of game.  I do think the term have proliferated a bit further than it probably should have since it was effectively invented to describe the renderer that many games had which optimized out pitch and roll from their projection.  With pitch and roll being a constant as a fundamental design of these renderers it's becomes clear that there's a distinction to be made between something that has a full 3D transformation matrix and the games that do not.  (Although roll can be emulated with screen space effects, pitch is definitely limited.)

 

I think where the term falls apart is that people then try to use it to describe game play, but then we find that the games don't necessarily fit into any well defined pattern.  Given that for the most part even "full 3D" games have limited yaw, pitch, and roll (i.e. hitboxes always being aligned), and how even within the same engine one game can be limited (i.e. Doom) and another could basically be full 3D (i.e. Hexen) the term really is useless there.  It would honestly be fine if the line was just vague since often times the labels we assign to games are (for example why is Hexen II fairly obviously just a first person shooter and not a first person role playing game), but in this case I feel like the line is so vague that it really doesn't describe anything of use.

 

Outside of first person shooters, games such as the axonometric projection games many of which do have a functional Z axis in their playsim but still have a strictly 2D renderer.  I think these are also perfectly fair uses for the term "2.5D" since it follows with the limited projection even if differently limited.  Not too much of a fan of using the term for when 3D objects are rendered to a 2D plane (i.e. New Super Mario Bros), but in the absence of any conflicting usage of the term for this genre of game I can't really object to it either.

 

Maybe there is a better term than "2.5D" that doesn't hijack a mathematical concept, but ultimately language is about conveying ideas.  We often use things in ways that are technically incorrect, but everyone understands the usage.  The most relevant example I can think of is how widespread the term "source port" is despite the fact that it originated from the fact that Doom had to be ported back from Linux to DOS.  If a change in platform didn't happen then it's not technically a "port."  Yet everyone knows that the term now effectively means "fan modification of the source code" or perhaps even more egregiously "reverse engineered recreation of a game."  (Which would involve neither source code nor porting in some cases.)  Despite how incorrect this term usually is people are pretty much comfortable with using it, although I'm sure there are a few exceptions.

 

It is unfortunate that the terms mathematical implications does result in some people drawing false conclusions.  I don't really think "Pseudo 3D" would make any difference in this regard.  It still mentions dimensions so there's going to be someone explaining the pseudo means it's actually 2D.  Even if a better term exists, I'll probably sooner convince everyone that Wolfenstein 3D doesn't have fixed size 64x64 sprites than for the term "2.5D" to go away.

 

If games like Wolf3D can actually fall under the "2.5D" label would honestly be a much more interesting debate to me.  I'm actually not sure where I stand on that.

[Yandere_Doomer]

pretty much the only thing that wasnt 3d was the sprites, they were just a still image turning towards you. but the rooms and everything else was 3d. 

 

[Maes]

On 12/26/2020 at 12:19 PM, Orchid87 said:

Ridge Racer and Daytona USA, despite being, as you say, vehicle sims, looked like the fucking future though and were released around late 1993/early 1994 as well. The latter even had texture filtering. Doom ran on home computers of course, but it's not like it couldn't be compared to those at the time.

 

Daytona USA and Ridge Racer used custom arcade hardware, so tons more powerful of what you could get at home at the time (there wasn't even hardware 3D acceleration at all, Hell, Windows 95 wasn't even out yet, in order to provide at least a standardized API for such functionality). But that being said, yeah, Doom didn't look all that much different visuals-wise, which in itself was quite amazing. The most noticeable difference was the smoothness/speed.

 

That being said, Need for Speed was ported to PCs at about the same time and ran even quite acceptably on my 486, which was so-so with Doom, so yeah, the future was there indeed. Daytona USA itself got ported to Windows in 1996 or so, and ran on a pure software renderer, at least initially (Pentium-class PCs only, of course), so that's telling of how quickly tech progressed in these days and how easy it was to be left behind. Ridge Racer never got a PC port, FWIW.

[Doomkid]

On 12/28/2020 at 5:30 AM, Dark Pulse said:

Hence, it's not quite a pure 2D engine, but neither is it quite a pure 3D engine. It's somewhere in the middle. And thus the term 2.5D was born, because it's fitting - you've got two full dimensions, and a partial third one that is fully implemented in some respects, but not in others.

This is definitely what I've come to understand 2.5D to mean. It's a colloquial term.

 

Really though, the longer I've thought about it, the less satisfied I am with it, because everyone seems to have different definitions - I've heard people saying other isometric games like Marble Madness, Snake Rattle N Roll, Mario RPG etc are "2.5D" as well, because they don't seem to realize it's just sprites moving on the X and Y axes and being either layered in front of, or behind one another based on their X and Y positions on screen.. It's one of those terms that, in an effort to simplify things, actually just added to the confusion for many people.

Edited December 31, 2020 by Doomkid

[Dark Pulse]

9 minutes ago, Doomkid said:

This is definitely what I've come to understand 2.5D to mean. It's a colloquial term.

 

Really though, the longer I've thought about it, the less satisfied I am with it, because everyone seems to have different definitions - I've heard people saying other isometric games like Marble Madness, Snake Rattle N Roll, Mario RPG etc are "2.5D" as well, because they don't seem to realize it's just sprites moving on the X and Y axes and being either layered in front of, or behind one another based on their X and Y positions on screen.. It's one of those terms that, in an effort to simplify things, actually just added to the confusion for many people.

By this logic, Zaxxon was a 3D shooter simply because it made use of axonometric perspective.

 

 

It's not. It's a 2D shooter.

 

The axis that'd be needed to make it true 3D would be the one that move the ship forwards and backwards, and you don't have that.

 

So really I don't buy any of that stuff. People need to look past the rendering perspective, and focus on the actual player/enemy movements. That's what decides 3D or not.

Edited December 31, 2020 by Dark Pulse

[Blzut3]

2 hours ago, Doomkid said:

Mario RPG

It's been awhile since I've played through the game, but I do believe there are a few instances in this game where there is indeed a Z axis (for example I believe there are a few instances of platforms you can be over and under).  Axonometric projection is a form of 3D projection, so yes even though it's very cheap to render using 2D hardware it does mean that axonometric games do technically have 3D renderers.  So you have a game which has a 3D playsim and 3D renderering, but is obviously not full 3D as we understand it today.  How does 2.5D not work to describe this?

 

If being an axonometric game by itself is enough definitely has room for debate just like Wolf3D could be debated to not fall under 2.5D despite being perspective correct.

 

Honestly though unless I'm just too selective on what groups I'm in, I honestly don't see too many people using 2.5D outside of first person shooters.  I know some people do, but for the most part there are more specific and equally concise descriptors for these types of games.

3 hours ago, Dark Pulse said:

The axis that'd be needed to make it true 3D would be the one that move the ship forwards and backwards, and you don't have that. 

If we look at player movements only, wouldn't you be proposing that a game like Space Invaders is a 1D game?

 

You also say to look at "enemy movements" and there's places in Zaxxon where they clearly move in along all three axes (36:30 in the video you link to name one place) even if the player is limited to only directly controlling two axes.

 

I really don't think you're going to get consistently satisfactory results by just looking at one aspect of a game be it play sim or rendering.

[ketmar]

4 hours ago, Doomkid said:

I've heard people saying other isometric games like Marble Madness, Snake Rattle N Roll, Mario RPG etc are "2.5D" as well, because they don't seem to realize it's just sprites moving on the X and Y axes and being either layered in front of, or behind one another based on their X and Y positions on screen..

but... most of such games internally has Z coordinate. Knight Lore (and other such games, like Head Over Heels) on ZX Spectrum are fully 3D internally. you can even push and stack objects in them, so their engines are more advanced than Doom engine! ;-)

[Maes]

5 hours ago, Dark Pulse said:

By this logic, Zaxxon was a 3D shooter simply because it made use of axonometric perspective.

 

The axis that'd be needed to make it true 3D would be the one that move the ship forwards and backwards, and you don't have that.

 

So really I don't buy any of that stuff. People need to look past the rendering perspective, and focus on the actual player/enemy movements. That's what decides 3D or not.

 

Good point, and one that I made several times in the past. But the degrees of control (DOC) vs the actual movement degrees of freedom (DOF) vs how the world is rendered, is another rat's nest.

 

For example, everyday cars and motorcycles only have "2D" controls, so to speak: you can really only go forward with ease, and you can only turn while you are moving (by yawing, in motorcycles you can also roll/lean), by choosing left or right with the steering or body inputs/countersteering. And yet, even with these limited controls, you can explore our very real 3D world (albeit with limitations). And if you argue that most roads could just as well be 2D, well, there are jumps as well as multi-floor buildings. So your 2D controls can take you to a very 3D place, if everything is just right ;-)

[Dark Pulse]

5 hours ago, Blzut3 said:

If we look at player movements only, wouldn't you be proposing that a game like Space Invaders is a 1D game?

 

You also say to look at "enemy movements" and there's places in Zaxxon where they clearly move in along all three axes (36:30 in the video you link to name one place) even if the player is limited to only directly controlling two axes.

 

I really don't think you're going to get consistently satisfactory results by just looking at one aspect of a game be it play sim or rendering.

No, it's 2D, as the enemies do move down. The player is very much only ever moving on a 1D plane though, but they "exist" in two dimensions, since they do have a height element to them. (A true 1D existence would be impossible, after all - even as a pixel, you'd have to be 1px tall.)

 

You do bring up a good point on Zaxxon though. Admittedly I'd say it's a bit nitpicky, though. In this sense, it may be more like Doom - there is some limited third dimensional stuff. Either way though, nobody is going to confuse it for a full 3D game; this is all still clearly scaled sprites.

 

But then again, you also got some pretty rare early pseudo-FPS examples, like Sega's little-known Arcade game, Last Survivor, a game that predates Wolf3D by about three years or so.

 

 

This, for example, is at least as 3D as Wolfenstein... even though just like in Wolfenstein, you never really have a Z Axis. Is this a 2D game, or a 3D one? Hard to say. If you say it's 2D, then so is Wolf. But it does have a tangible "height" dimension, even if you really don't make use of it.

 

That's where things get tricky. Some will say this is 3D, as this clearly is projecting a 3D space. Some will say this is 2D or 2.5D due to you being on relatively fixed planes and effectively having two axes of movement. Which one is right? Both, arguably.

Edited December 31, 2020 by Dark Pulse

[Doomkid]

You guys have convinced me that some isometric games are 2.5D. I was really just referring to the fact that “raising on the Z axis” in these games really just translates to sliding a 2D sprite upward on the screen. You could print all the levels and sprites as 2D bits of paper and lose nothing meaningful - whereas with Doom, anything less than a 3D model of the world would result in a substantial loss.

 

In terms of logic, id say these games are clearly 3D. You have to think in a 3 dimensional space to progress. It’s just that you’ll never see a sprite shrink as it gets further away, for example. Purely from a technical perspective, what we are seeing as 3D movement in an isometric game is just clever movement of sprites on the X and Y axes, which is unlike Doom, which cannot use clever X and Y movement to simulate Z movement, due to it being first person rather than isometric.

 

Of course, if you have to climb a cliffside in an isometric game, you still have to think in a 3D way to solve the puzzle. It’s just that there’s no actual 3D rendering or whatever of any kind. I hope this makes some sense, and is indeed accurate.. I guess what I’m saying is that if isometric games are using a close enough approximation to 3D to cross into being “2.5D”, then Doom itself cannot wear that label, as it is far more 3D than those games. (Then again, I’m of the mind that Doom solidly qualifies as 3D other than all the objects being represented by sprites, so I guess that adds up!)

Edited January 1, 2021 by Doomkid

[BladeWolf]

Surprisingly, @Doomkid's Myths video was immediately recommended to me after watching this video. It's always nice to know more insight on how the BSP handled environments, and sprites were actually 3D, in terms of hitbox. But Doom definitely hits the middle ground, since levels and environments are 2D level data, rendered to give the 'illusion' of 3D. 

 

The host of the Game Theory video, however, had passed away in 2018. RIP Robbie.

Edited January 1, 2021 by BladeWolf

[Blzut3]

51 minutes ago, Doomkid said:

it’s just that there’s no actual 3D rendering or whatever of any kind. I hope this makes some sense, and is indeed accurate..

Emphasis mine.

 

Careful with your terminology here.  Mathematically speaking, there is technically 3D rendering going on, it's just that the projection used has the convenient property of not requiring texture scaling.  An axonometric projection does however map 3D space onto a 2D plane just like perspective projection does.  The fact that this optimizes down to just layering sprites is irrelevant to if it's 3D or not.

 

So the correct thing to say is "there's no perspective 3D rendering."  Which I think most people would agree is "more 3D" than axonometric since it has less visual ambiguity and matches how the real world looks.

[magicsofa]

14 hours ago, Dark Pulse said:

(Zaxxon)

 

It's a 2D shooter.

 

The axis that'd be needed to make it true 3D would be the one that move the ship forwards and backwards, and you don't have that.

But you are moving on that axis. Just because you can't control the movement, doesn't mean the axis isn't there. Or are you telling me the lasers actually move on the same plane as the ship?

[Dark Pulse]

25 minutes ago, magicsofa said:

But you are moving on that axis. Just because you can't control the movement, doesn't mean the axis isn't there. Or are you telling me the lasers actually move on the same plane as the ship?

They don't - they have their own independent 2D axis they move on. Clever use of perspective doesn't make it any different.

 

In a top-down shooter, your shots move forward. While capable of moving backwards, they never do so. They do have a "width" to them (which in Zaxxon is actually more of a "length"), so they are a 2D object. But you won't ever see them have a third dimension, because they can't hit anything "above" or "below" them.

 

After all, the 2D shooter would generally fall flat on its ass (no pun intended) if enemies could simply... you know, fly up or down. In Zaxxon they can actually do this, but generally speaking, considering the concept of thinking in 3D space was very new at the time, when an enemy ship charges the player, they fly in a straight, 2D Shooter-esque line right towards the player, just as the shots do.

 

If you could aim a shot up or down, or an enemy could do likewise, and hit something above/below their current plane, then the lasers could arguably be considered 3D. As it's not possible to do that, it's basically very clever 2D. Your shots may well move "forward" but they have their own limited axis; they will never move from side to side; nor up and down.

 

I'd argue that it would need a bit more than that to be actually 3D - an enemy would need to be able to fly up alongside you, turn, and blast you in the side for it to be a fully 3D implementation; something that is very much impossible to do in Zaxxon. In that sense, the limitations of the perspective become a bit more apparent.

Edited January 1, 2021 by Dark Pulse

[Kappes Buur]

A lot of discussion has gone on about this,

but the simple fact is that the game is clearly rendered as 3D

but constructing a map is 2D.

[Edward850]

1 hour ago, Kappes Buur said:

but constructing a map is 2D.

But building a map is 3D, it explicitly has height information that you control (and are in some respects expected to as doors would be unworkable otherwise).

[Kappes Buur]

1 hour ago, Edward850 said:

But building a map is 3D,.....

 

How so?

 

Yes you give sectors a height, but that does not negate the notion that constructing a map is basically a 2D affair. There is no 3D height information displayed when looking at the raw map image.

 

 

The 3D nature of the map is only revealed in the 3D Preview Mode or when playing the game.

 

 

 

[chungy]

19 minutes ago, Kappes Buur said:

 

Yes you give sectors a height, but that does not negate the notion that constructing a map is basically a 2D affair.

What more does 3D require than length, width, and height?

 

This is effectively the same as claiming that everybody that designs a house to be built in the real world is actually building a 2D house just because of how it looks on the blueprints.

Edited January 1, 2021 by chungy

[Kappes Buur]

A house is designed first of all in a topdown view blueprint, which is 2D.

 

 

The 3D aspect is only revealed when the view is drawn as an isometric view or sideviews.

 

So it is the same with an editor like DB2, UDB, Eureka, Slade3, etc.

Constructing a map as a true 3D design requires an editor like GTKRadiant or the DOOM3 editor.

Edited January 1, 2021 by Kappes Buur

[Cruduxy Pegg]

Pretty sure you can raise and lower floors in Doom Builder during 3D render mode.

[boris]

4 minutes ago, Pegg said:

Pretty sure you can raise and lower floors in Doom Builder during 3D render mode.

 

There are even hotkeys to do that in 2D mode.

 

Just because one of the representations of the map is in 2D doesn't mean anything. When one maps for Quake and uses one of the 2D views in the editor that doesn't suddenly mean the map is construced in 2D.