Things about Doom you still don't understand

[bofu]

One thing I don't understand is why id never made a patch for the Doom 2 IWAD that fixes the stuck or unresponsive enemies in several maps and barrels-inside-walls in MAP02 that got introduced some time after v1.666. Or, you know, the crash in MAP06.

 

On a sillier note, I don't understand where those doors go when they rise up into the ceiling but there's a sector nearby with the sky texture that is clearly lower than where the door would be raising into. My immersion is utterly broken!

[ShallowB]

Funny you should mention Super Metroid, I just got done playing through the original trilogy.  I only ever had Metroid 2 at the time, so I wanted to see what the others were like.  It's wild how much better those games got at signposting while still making the game feel like you were exploring and uncovering secrets.  NES Metroid straight up blocks progression behind walls and floors that you can only open by hitting them with specific weapons even though they look identical to all other walls and floors, and that feels frustrating and awful.  Even if you can only possibly interact with anything in that game by shooting things, requiring the player to get to Ridley's hideout by going to the bottom of the second vertical shaft and placing a bomb on the second tile from the right is a pretty big ask when there is no indication at all that they are supposed to do that.  By the time you get to Super Metroid, you can easily find your way through the game from start to finish, and secret paths are kept exclusively for secrets.  I don't think that's "hand holding" so much as it's just better map design.

 

I think the Metroid 2 remake takes things a bit too far, straight up marking where secrets are on the map and giving you an ability to highlight breakable walls.  It almost trivializes the player's own role in the game.

[ShallowB]

15 minutes ago, bofu said:

One thing I don't understand is why id never made a patch for the Doom 2 IWAD that fixes the stuck or unresponsive enemies in several maps and barrels-inside-walls in MAP02 that got introduced some time after v1.666. Or, you know, the crash in MAP06.

 

Speaking of which, why didn't Bethesda do it in any of the versions of the IWADs they released?  Ordinarily I'd be against changing anything about a game you didn't actually develop yourself in the interest of preservation, but Doom is already pretty well documented with many official versions available, and Bethesda actually *did* make some non-insignificant changes to the IWADs already anyway, like removing the Wolfenstein references, changing the medkits, and adding a couple of their own secret maps.

 

Why not fix the obvious bugs while they're at it?

[Doomkid]

4 hours ago, ShallowB said:

It seems silly now because we’ve been playing user-made wads of varying quality for 30 years now and we’re used to making Doomguy hump anything that looks remotely out of place, but when Doom 2 was a brand new game, the silver bars could understandably confuse people.

Well, I can only speak for myself, but when I first played Doom2 I was either 6 or 7 and all I had played prior to Underhalls was shareware E1 and Entryway. I saw the red bars at the other end were pressable, so why wouldn't the silver ones be? Plus, jail cells are openable in the real world!

 

All I'm getting at is that at a certain point, the flaw isn't on the mapper but on the player. I feel like they're pretty clearly choreographed in several different ways - similarly, when I make platforms with the METAL texture with a key or powerup right on top and the player runs around in circles saying "how do I get this?!" without pressing on the bloody lift-like texture it's made of, the fault is not mine as the mapper but theirs as someone who doesn't want to spend even a millisecond exploring or trying things out.

 

Above all that - I think "the search" can sometimes be fun in and of itself. If handing the progression to them on a silver platter is already not enough, I don't feel the impetus to put a big glowing red alarm on the already-shiny silver platter, hehe.

 

I've definitely played numerous cryptic maps, and I don't like that much at all, but I also feel like my definition of what is cryptic is (unintentionally) out of step with the current mapping zeitgeist. I consider Doom 1 and 2 the baseline for mapping itself, but doing things that are very much like what Doom 1 and 2 did themselves is now seen as cryptic, because no one plays the damned iwads anymore - or at least that's how it seems!

 

(Also as an aside David's video on Doom's visual language is amazing - as all of David's Doom development videos are - but I still feel like it's best seen as a guideline rather than gospel)

[Edward850]

3 hours ago, ShallowB said:

and Bethesda actually *did* make some non-insignificant changes to the IWADs already anyway, like removing the Wolfenstein references, changing the medkits, and adding a couple of their own secret maps.

Bethesda in absolutely no way did this. Id didn't even do this. It was an undocumented thing from a Nerve developer that was subsequently removed.

Edited September 14, 2022 by Edward850

[Gez]

5 hours ago, DavidN said:

Personally I’ve always wondered why megagenius John Carmack never parameterized linedef actions from the beginning - I know Doom was made in a huge hurry, but after the 127th time Sandy asked if he could have a new action that raises a sector’s floor by 80 units if you shoot a linedef and this one should be repeatable, you would think he’d have realized they’d benefit from being more customizable. Maybe they really were just going so headlong into it that there wasn’t time to alter how the actions were defined!

That part of the code was actually Romero's, and that made sense since he made maps in addition to coding, so that when he wanted a new effect he'd just implement it right away.

[ducon]

How did the imps go up there?

[Pechudin]

10 hours ago, bofu said:

On a sillier note, I don't understand where those doors go when they rise up into the ceiling but there's a sector nearby with the sky texture that is clearly lower than where the door would be raising into. My immersion is utterly broken!

 

All doors are actually roll-up doors. Fixed. Immersion restored.

[Solmyr]

4 hours ago, ducon said:

How did the imps go up there?

[Broken pic]

Where? I assume they are on an inaccessible area, as monsters teleports randomly because hell is chaotic, then those imps got screwed by random chance.

[Gez]

It's the E1M2 room near the exit, the one with the big downward lift and the secret passage that lets you reach one of the side ledges. There's no path to the other two ledges. And yeah, "they just teleported there" is as good an explanation as any...

[ducon]

In fact, I regret sometimes that some zombie ammo is not grabable.

[Gez]

Doom needed a fishing pole to grab items that are out of reach.

[HotCoffee]

On 9/13/2022 at 12:03 AM, jmpt16 said:

how DO you compile doom's source code?

Download the linux source code from github and compile with ```make```

https://github.com/id-Software/DOOM/tree/master/linuxdoom-1.10

[volbound1700]

On 9/13/2022 at 12:48 AM, Sonikkumania said:

There's a huge arrow on MAP13 : Downtown in Doom 2. Now that I think of it there's also arrows in MAP05: The Waste Tunnels, in the dark room right from the spawn area. As a kid I always thought the latter was very cool, like a disco or something. It really fed my imagination.

 

I think Sandy Petersen made those levels and he has a Youtube channel where he explains some of his concepts.  I think the arrows were simply meant to direct the players to go in the correct direction (at least for level 13).  

[Alex S.]

On 9/13/2022 at 5:31 AM, Gez said:

Because of the automap.

 

void AM_drawFline(fline_t *fl, int color)

...

  					// For debugging only
  				if (   fl->a.x < 0 || fl->a.x >= f_w
      				|| fl->a.y < 0 || fl->a.y >= f_h
      				|| fl->b.x < 0 || fl->b.x >= f_w
      				|| fl->b.y < 0 || fl->b.y >= f_h)
  				{
    				fprintf(stderr, "fuck %d \r", fuck++);
    				return;
  				}

Doom and Hexen have the same code. I suppose this is also true for Strife.

 

Ha! Thank you I never knew this and honestly should have just looked at the source myself. Cheers man!

[PKr]

I bet this has already been answered somewhere before, but what exactly is happening in e3m1 in v1.2 with the floor textures here?

[erzboesewicht]

In arch-vile jumps, I don't understand how you can prevent deviations from your intended direction where you're propelled, i.e. prevent to be propelled diagonally if you aim forward. For example, in Cydonia MAP31 at the three consecutive jumps to the exit area, I was sometimes propelled diagonally to the left by up to 45 degrees instead of straight ahead even if "aiming" forward in a straight line.

 

Has it perhaps to do with the relative position of the AV to the player, i.e. if the AV is located diagonally to you, then you'll deviate from your intended direction?

[Koko Ricky]

On 9/15/2022 at 8:19 AM, volbound1700 said:

 

I think Sandy Petersen made those levels and he has a Youtube channel where he explains some of his concepts.  I think the arrows were simply meant to direct the players to go in the correct direction (at least for level 13).  

 

Just wanted to say, in considering whether the arrow was indicative of unclear progression (which some would argue is the case), I have seen arrows guiding the player in 2D and 3D games, including other Doom levels. It's a standard prop in gaming. What would make it problematic is if the progression is so cryptic that many arrows are being used. 

[Kyka]

The thing I would love to understand better and don't really understand much at all, except in principle, is how the Doom engine takes things like sprites and textures and flats, and arrays them around you in a 3 dimensional space. How does the doom engine take the data from a map layout and turn it into a 3 dimensional space, rendered on a 2 dimensional screen. I am intrigued by the wizardry that such a process  entails. And I know nothing about it. Other than conceptually, I don't even really know what an engine is. Well obviously it is a bunch of code, but what sort of code? Damn I am ignorant of this stuff.

 

The other thing I don't understand is why someone, even conceptually, would want to rebuild tekwar on the GZDoom engine, as being discussed, again conceptually, in another thread. Like, come on.

[Edward850]

4 hours ago, erzboesewicht said:

In arch-vile jumps, I don't understand how you can prevent deviations from your intended direction where you're propelled, i.e. prevent to be propelled diagonally if you aim forward. For example, in Cydonia MAP31 at the three consecutive jumps to the exit area, I was sometimes propelled diagonally to the left by up to 45 degrees instead of straight ahead even if "aiming" forward in a straight line.

 

Has it perhaps to do with the relative position of the AV to the player, i.e. if the AV is located diagonally to you, then you'll deviate from your intended direction?

The player is propelled vertically but there's an explosion that occurs independently at the archvile fire that appears in front of you. Because it doesn't travel with you constantly, the explosion may hit you at an angle if you aren't moving dead on at it.

Edited September 17, 2022 by Edward850

[Koko Ricky]

29 minutes ago, Kyka said:

The thing I would love to understand better and don't really understand much at all, except in principle, is how the Doom engine takes things like sprites and textures and flats, and arrays them around you in a 3 dimensional space. How does the doom engine take the data from a map layout and turn it into a 3 dimensional space, rendered on a 2 dimensional screen. I am intrigued by the wizardry that such a process  entails. And I know nothing about it. Other than conceptually, I don't even really know what an engine is. Well obviously it is a bunch of code, but what sort of code? Damn I am ignorant of this stuff.

 

The other thing I don't understand is why someone, even conceptually, would want to rebuild tekwar on the GZDoom engine, as being discussed, again conceptually, in another thread. Like, come on.

 

Take this with a grain of salt as I'm not an expert. That said...

 

Doom's maps are built in two dimensions, X and Y. When you adjust the heights of sectors, you're accessing a very limited third dimension. So you have the floor/ceiling of the sector (rows), separated by walls (columns). As @Gez mentioned, "it's not a conventional polygon renderer. It renders columns (and flood-fill rows)." Clearly that indicates Doom features texture-mapped polygons, but they lack pitch/tilt information, and the kind of polygons Doom can render are very limited. 

 

As for why TekWar is being rebuilt through GZdoom, there is clearly enough interest in the game that it would warrant developing the means to play it on a modern computer. We're also the Doom forums, not the Build forums, so for the few here that want to play TekWar, a feature-heavy source port like GZDoom makes sense.

[PKr]

32 minutes ago, Kyka said:

The thing I would love to understand better and don't really understand much at all, except in principle, is how the Doom engine takes things like sprites and textures and flats, and arrays them around you in a 3 dimensional space. How does the doom engine take the data from a map layout and turn it into a 3 dimensional space, rendered on a 2 dimensional screen. I am intrigued by the wizardry that such a process  entails. And I know nothing about it. Other than conceptually, I don't even really know what an engine is. Well obviously it is a bunch of code, but what sort of code? Damn I am ignorant of this stuff.

 

The other thing I don't understand is why someone, even conceptually, would want to rebuild tekwar on the GZDoom engine, as being discussed, again conceptually, in another thread. Like, come on.

I would recommend watching this three part series:

It's not exactly about Doom, but should explain quite a lot about Doom nonetheless.

[Gez]

58 minutes ago, Kyka said:

The thing I would love to understand better and don't really understand much at all, except in principle, is how the Doom engine takes things like sprites and textures and flats, and arrays them around you in a 3 dimensional space. How does the doom engine take the data from a map layout and turn it into a 3 dimensional space, rendered on a 2 dimensional screen. I am intrigued by the wizardry that such a process  entails. And I know nothing about it.

The best explanation of how it all works can be found on Fabien Sanglard's site, who has also written in-depth explanations of the workings of Wolfenstein 3D, Quake, Duke Nukem 3D, Doom 3, and more!

https://fabiensanglard.net/doomIphone/doomClassicRenderer.php

For the definitive source, he also wrote a full book: https://fabiensanglard.net/gebbdoom/index.html

 

24 minutes ago, PKr said:

It's not exactly about Doom, but should explain quite a lot about Doom nonetheless.

It's a Wolfenstein 3D-style raycaster, so it doesn't really explain anything about how Doom works. Likewise, there's this video that claims to be about Doom-style rendering, but in fact it explains Build-style rendering...

Edited September 17, 2022 by Gez

[Kyka]

@Koko Ricky Thanks for the reply. Watching a couple of the vids recommended above has really given me a basic grounding in how engines work.

 

@PKr Thanks so much for that video series. Ive just watched all three. My mind was honestly blown. I feel like I was watching the source code of the universe. Looking at naked singularities beyond black holes. Now I know what a game engine does. Obviously what was shown in these vids was introductory, and we're not at the point where I can decompile Unreal Engine 5, but even seeing the basics was incredible. Haven't done any real maths since high school, and am not a programmer, but I was still able to follow along, take a couple of notes and conceptually understand what he was doing. These videos answered so so many of my questions, but raise so so many more. Do modern game engines still render textures as arrays of three-numbered code for each pixel, or are they able to 'hang' entire textures like posters in a 3D space? Bumpmapping? Hitboxes? Sectors? How color gradients are overlaid to simulate lighting. etc etc. Collision detection. But point being, all of those more complex things are built on the foundation of making a simple engine. I noticed that 3D sage also has a video about the Doom engine itself. Cheers. :)

 

@Gez As ever thanks for the reply. I haven't looked at it yet, as my brain is still full from watching @PKr's video series.  But I will get to it soon. Appreciated.

[SMG_Man]

On 9/13/2022 at 6:09 PM, Solmyr said:

speaking of dumb, i can't seem to figure out how to implement transparent doors in Vanilla Doom, i've read forum topics about it, and saw a video tutorial by joe-ilya, but despite that, i can't get them to work properly.

 

For me, following this tutorial was pretty easy to understand and worked perfectly. If you've already looked at this one and still don't get it, let me know and I can try either making a more step by step post or commentated video about it. It's a very neat effect to have in your maps. (Note: from my testing, using this method to make transparent doors works like a charm in Chocolate and Crispy Doom. In GZDoom, the effect works in Hardware-accelerated mode, but breaks when using either the Doom or True-color Software Render.)

[SaladBadger]

honestly this is more of a "I haven't done sufficient study" thing more than anything but I'm still not sure what it is in the mess of polar coordinates Doom does for perspective-correct texture mapping in the outer loop of the wall and floor/ceiling renderers.

 

it's a little more clearcut in the prerelease code where everything is way more by the book, but Carmack's polar coordinate stuff for the release game proves more confusing.

[volbound1700]

On 9/17/2022 at 1:36 PM, Koko Ricky said:

 

Just wanted to say, in considering whether the arrow was indicative of unclear progression (which some would argue is the case), I have seen arrows guiding the player in 2D and 3D games, including other Doom levels. It's a standard prop in gaming. What would make it problematic is if the progression is so cryptic that many arrows are being used. 

 

True but it was far more common back then.  Generally how I and many people approached shooters in that era was to focus first on killing off the monsters and then focus on beating the level itself.  Basically with Level 13, you went around the city killing everything before you figured out how to progress.  

 

There have been some Doom 2 WADs that I got lost on (usually related to switches).  Level 15 in Doom 2 is also very challenging to figure out the first time you play it.

 

Doom 64 also has some very confusing levels to figure out how to advance in.  

 

In summary it seems to be a product of that time.  However, I kind of like it versus the rail hand-holding of more modern shooters.  

[CasualScrub]

On 9/12/2022 at 11:25 PM, xScavengerWolfx said:

Why everyone thinks Brutal doom is such a great mod to play Doom and/or Doom 2 with. I hate brutal doom, it ruins the experience of classic old school FPS. 

I take it you haven't explored Doomworld for very long, have you. There are plenty of people who despise BD.

 

As for why people enjoy it though (from someone who enjoys BD), I enjoy the carnage, the different weapons, the animations, etc. I'm not that interested in playing vanilla much of the time, I usually play the game modded in some way. Different strokes for different folks.

[Captain Keen]

On 9/13/2022 at 10:53 PM, bofu said:

One thing I don't understand is why id never made a patch for the Doom 2 IWAD that fixes the stuck or unresponsive enemies in several maps and barrels-inside-walls in MAP02 that got introduced some time after v1.666. Or, you know, the crash in MAP06.

This is a genuine question: I thought they did fix that?

 

I pulled various versions of both Doom 1 and Doom II to check them out and if I recall v1.9 fixes stuck enemies such as the arachnotron in Map 11 on UV. I believe that was an official patch? Please correct me someone if I’m wrong. Before downloading that version I had been using the initial build from the Sep 1994 release.

[TheSlipgateStudios]

Why is there wood in hell? We may never know.