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hardcore_gamer

Why were slopes removed from Doom?

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While watching a documentary about Doom recently there was this brief bit that said the doom engine originally was able to create slopes but that this was later removed. Why was it removed? Slopes can add a lot to a level.

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Shadowcaster, developed on Carmack's research engine done between Wolfenstein 3D and Doom, had slopes, but none of the known Doom alpha builds are capable of doing slopes (well, as far as we're aware) so presumably it never actually made it into Doom's engine. So far as I'm aware the Shadowcaster engine did not directly evolve into Doom.

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I believe it was considered and Carmack found the math would be too complex and expensive at the time to do that kind of calculation for arbitrary sector shapes rather than for fixed-space grid cells. (I've said pretty much this exact thing in another thread I think....)

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Doom II was originally going to have sloped floors and ceilings, to the best of my recollection.

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I think most machines were unable to run that complex math so many times. It was groundbreaking / revolutionary simply to have 2.5 3D floors

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Doom was pushing the hardware to its limits already and was not running at constant fullspeed on most PCs of the time, depending on the map. Slopes would make the performance even worse and would have prevented some of the console ports. And to put slopes in a map would mean that other detailing would have to be simplified instead.

 

Also, the engine would have more rendering bugs and physics bugs, surely.

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I found an old post that describes how it looked. I would be interested to see a screenshot or video of how it looks like (can't find one on Google and the walkthroughs on YouTube are very long).

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1 hour ago, Maisth said:

I believe it would interrupt in the Game's 2.5D Mode that it had

What?

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1 hour ago, Maisth said:

I believe it would interrupt in the Game's 2.5D Mode that it had

You sure said a bunch of words but together they don't string a rational sentence.

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I would also like to see some screenshots or even better a video and a timestamp.

 

I checked out a video of gameplay and it was just about going bruce-lee on some poor plants.

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6 hours ago, hardcore_gamer said:

While watching a documentary about Doom

What documentary? Where? Who said this? Were they quoting a source?

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3 hours ago, axdoomer said:

I found an old post that describes how it looked. I would be interested to see a screenshot or video of how it looks like (can't find one on Google and the walkthroughs on YouTube are very long).

My guess is it would look like the slopes in Duke 3D's Build engine, another software engine game, and probably the most comparable engine.

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I heard this same thing years ago but and have never been able to find a source or anything further on the topic.. Apparently, according to whatever it was I was watching or reading, Carmack and co didn't want to blow their whole load on Doom, saving stuff like slopes and 3D floors for later releases. Not only would it strain hardware of the time, but they wanted whatever came after Doom to still have it's share of engine features that wowed people, essentially. Take this with a grain of salt because the sauce is (apparently) long gone, but it still seems like a fairly sensible explanation.

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7 minutes ago, Doomkid said:

Carmack and co didn't want to blow their whole load on Doom, saving stuff like slopes and 3D floors for later releases.

I don't believe this for a moment. Everything from that time period suggests that they wanted to do as much as they could with every game. Purposely "holding back" features would not have been their style, at all.

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I'm inclined to agree, I sent both Johns a tweet asking for clarification. With some luck one of them will respond

 

EDIT - Romero responded :)

 

Quote

It would have slowed the engine down. Straight vertical walls and flat ceilings and floors is part of the speed formula.

There's that one solved!

Edited by Doomkid

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Slopes and Doom's entire movement code really do not mix well. There's a shitload of fudging code in ZDoom to make it work and even that isn't enough to handle everything well.

 

Aside from performance issues this may also have been a contributing factor for ditching them.

 

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12 hours ago, InsanityBringer said:

Shadowcaster, developed on Carmack's research engine done between Wolfenstein 3D and Doom, had slopes, but none of the known Doom alpha builds are capable of doing slopes (well, as far as we're aware) so presumably it never actually made it into Doom's engine. So far as I'm aware the Shadowcaster engine did not directly evolve into Doom.

I'll add that the slopes in Shadowcaster are used only once, and of course they're used on a ceiling -- I doubt the engine would have handled movement on a slope. Also it looks pretty bad actually, with the texels swimming awkwardly around, like there are mathematical errors in the texture projection code for a sloped surface.

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That's the best explanation I think we're going to get. Makes me wonder what Ken Silverman did that made slopes look less fucked up on the Build Engine...

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2 hours ago, GoatLord said:

That's the best explanation I think we're going to get. Makes me wonder what Ken Silverman did that made slopes look less fucked up on the Build Engine...

Well that's a totally different engine with much higher requirements than Doom. Also, that engine is clunky as fuck, held together by bubblegum and gypsy tears.

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Considering Silverman was still in high school when he designed the engine, it's unsurprising that it's less elegant than Carmack's, who seemed to have this knack for distilling emerging game technology down to its most functional components.

 

To go briefly tangential, the Quake engine had a similar impact. It didn't support static skyboxes, alpha transparency or keyframe interpolation, despite these features being possible. It came down to, as in idtech1, ensuring that the most fundamental aesthetic features were front and center (i.e. full 3D rendering, lightmaps and OpenGL support), rather than risking instability by adding superfluous features. 

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[pedant]

 

OpenGL support is hardly fundamental for Quake. It wasn't there when the game was released, and when it was added, it was a semi-official experimental build - mostly useful for its performance on crappy CPUs (which didn't stop it from ruining Quake for several generations of misguided players).

 

[/pedant]

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9 hours ago, Gez said:

I'll add that the slopes in Shadowcaster are used only once, and of course they're used on a ceiling -- I doubt the engine would have handled movement on a slope. Also it looks pretty bad actually, with the texels swimming awkwardly around, like there are mathematical errors in the texture projection code for a sloped surface.

Do you remember on which level it is used? I would really like to see it. 

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IIRC it's the first level with lava. There's an area of ice and a small puzzle where you have to drop stones on pressure plates, and it makes lava appear in two "trenches" (scare quotes because everything is flat, obviously) and the ice "melts" with the slopes appearing on the ceiling after that. (They aren't there from the start.)

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How about their use in "In Pursuit of Greed"? It seems to be more extensive, if this screenshot is anything to go by anyways:

InPursuitOfGreed.png

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You can see it appearing here when the ceiling raises: https://youtu.be/jFLJVzBNGto?t=7m46s

 

You can see it again here where it has fully appeared: https://youtu.be/jFLJVzBNGto?t=8m8s

 

OwWfVwpg.png

Like in In Pursuit of Greed, the game may be using polygons to draw the floor and ceiling, but I don't believe Shadowcaster is meant to do sloped ceilings. In Pursuit of Greed uses a more advanced engine built  on the Shadowcaster engine. I believe the texture is being drawn like if it was an horizontal ceiling. By looking at the video, it made me think of Doom when you have a ceiling texture that bleeds over a linedef when the upper texture is missing. That's the impression that I have, because the texture is not animated, but when the player moves, the texture moves. It does have the shape of a slope though, probably because it's made of polygons like its successor, but the engine still renders its texture like if it was like any other ceiling. I'd say it's a bug. 

Edited by axdoomer

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3 hours ago, Quasar said:

How about their use in "In Pursuit of Greed"? It seems to be more extensive, if this screenshot is anything to go by anyways:

It is, and has working floor slopes AND dynamic floor slopes. Haven't played the game in forever though, so I can't remember much.

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From Masters of Doom:

 

Quote

He [Carmack] returned to the id apartment with the re-

sults of his labors on the Shadowcaster engine. It was, everyone immediately

saw, quite a leap. There were two noticeable firsts: diminished lighting and

texture-mapped doors and ceilings. Diminished lighting meant that, as in real

life, distant vistas would recede into shadows. In Wolfenstein, every room

was brightly lit, with no variation in hue. But, as any painter knows, light is

what brings a picture to life. Carmack was making the world alive.

For greater immersion, he had also learned how to apply textures to the

floors and ceilings, as well as add variable heights to the walls. The speed was

about half that of Wolfenstein, but since this was an adventure game, built on

exploration, it seemed appropriate to have a steadier pace. The leaps didn’t

come easily to Carmack. It took a hefty amount of time for him to figure out

how to get just the right perspective down for the floors. But his diligence and

self-imposed isolation had paid off in a big way. He even had slopes on the

floors, so the player could feel like he was running up or downhill. Kevin

spent about twenty minutes just running up and over a little hill in the game.

It was incredible. And, it was clear, it was time for id to turn this technology

into their next game.

 

 

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Well that's certainly telling! I wonder if maybe the slopes ended up being really glitchy and weren't worth implementing in the end. I'd love to know more.

@Da Werecat I agree that it actually fucked up some of Quake's graphics (most noticeably the dynamic lighting), but in 1996 very few games utilized texture filtering and the N64—which was brand new at the time—was the first console to support texture filtering, an indicator of how uncommon its implementation was. I ultimately like how software rendering looks better, but I'd also argue that it was an important step toward modern rendering techniques. 

 

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