What is the weirdest bug you have ever encountered in a Doom WAD?

How about moving so fast down an obscenely deep shaft only to appear at the very top of the ceiling of that sector? I mean, that's pretty fucking weird, despite the obvious cause.

Oooh, and even better ZDoom-related bug/"feature"...
If you set either the Friction or Wind sector flags and give the sector a type of "end level when health <= 10%", you become invulnerable at 1% health. I never understood exactly why this happens, but it has been immensely useful in rocket jumping wads where one never needs to worry about suiciding. Graf Zahl is my hero just because of this one discovery.

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despite the obvious cause.

What would that be?

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EarthQuake said:

How about moving so fast down an obscenely deep shaft only to appear at the very top of the ceiling of that sector? I mean, that's pretty fucking weird, despite the obvious cause.

Heh, that's one of my most favorite glitches in Doom.

Reaper978 said:

What would that be?

http://www.speedyshare.com/411799371.html

(be sure to try it in vanilla/Choco Doom as well! It actually gets really freaky if you sit it out to the end)

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Nuxius said:

Heh, that's one of my most favorite glitches in Doom.


http://www.speedyshare.com/411799371.html

(be sure to try it in vanilla/Choco Doom as well! It actually gets really freaky if you sit it out to the end)


That was pretty cool! Never seen that happen in the game before.

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I've experienced a bug in a map I made long ago for my first TC. It was a lift that fubared and in an instant went super low so much that the Doom engine couldn't properly handle it and I got some very weird visual glitches. Hard to explain really. But I am sure someone like Myk will know what I am talking about.

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It sounds like a variant of the tag 0 issue, maybe.

Quasar said:
This was probably an intercepts overflow, however, and not a spechits overflow, as those occur on mobj motion as opposed to firing of tracers.

Indeed, that was a brain fart and I meant intercepts, as spechit overflows are pretty harmless (and not the cause of all-ghosts and the like). Post fixed, thanks!

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myk said:

Heh.


ROFLMAO!!! This one also caused a sound glitch in ZDoom, and even idclipping out of the pit made you stick to the ceiling, but as soon as you orbited back to it you would fall back in :-D

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myk said:

It sounds like a variant of the tag 0 issue, maybe.

I dunno. it didn't happen every time. It could happen if you fucked around with the lift too much IIRC.

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I was trying to replicate Earthquake's "obscenely deep shaft" bug, and I learned that if you have a 320 x 320 sector that is over 100,000 units deep, it creates an invisible wall and no hole.

Edit : actually it's more like 50,000 now that I've narrowed it down a little more.

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Shadow Dweller said:

I was trying to replicate Earthquake's "obscenely deep shaft" bug, and I learned that if you have a 320 x 320 sector that is over 100,000 units deep, it creates an invisible wall and no hole.

Edit : actually it's more like 50,000 now that I've narrowed it down a little more.


The maximum depth and height one can set "normally" appears to be -/+32767 units, and when the extremes are touched the engine doesn't work quite normally, for some reason. Doombuilder at least won't allow you to set unit heights above that limit, even with a BOOM configuration, so maximum height difference is 65534. Notice how the usual lower limit for two's complement arithmetic (-32768) is not included.

In any case, exceeding those would likely cause a rollover, during the dropping phase, where your view is momentarily "squashed". Also, setting both to maximum values causes a visual rendering glitch as well, and you appear "suspended" in an endless sector.

If you enter it, you are just suspended in it, unable to move forward (you can however move to an adjacent "normal" sector.

If however you idclip in the anomalous sector, you just "float" forever with any momentum you might have.

If you teleport in it, if you try to walk you see both the ceiling and the floor bobbing in opposite directions like a concertina, and you will be unable to move. Shots just explode in your face.

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The behavior of the DOOM engine with extreme heights is interesting but somewhat academic to discuss since areas as short as 2500 units deep can cause crashes (Caves of Circe in Hexen has a spot which can reliably crash the game in this manner).

DOOM crams clipping values for the texture mapping code into 16-bit integers, but in an attempt to preserve some of the decimal precision from the initial fixed-point values, only shifts said values down by 12 bits, leaving 4 decimal bits. But if the resulting value is still out of range for a signed short, then on the conversion and storage into the clipping arrays the value typically becomes a very large positive offset. Since y values increase as you go toward the bottom of the screen, a really large value is telling the game engine to draw off the bottom of the screen.

Usually this will fail in R_DrawColumn and cause an immediate venetian blinds crash. Sometimes it will instead survive up til R_MakeSpans and trash the majority of the game's BSS data segment (where uninitialized global variables/arrays/structures live in memory). This will also crash, but has the included effect of making it nigh impossible to debug should it be caught in a debugger, and can have bad side effects such as trashing the configuration file.

Thus I don't recommend using really tall areas in vanilla or BOOM maps :) Some modern ports (EE included) now have tolerance for really tall areas, but at the utmost extremes weird things can still happen, just as they do on the horizontal plane near the +/-32000's.

BTW, disappearing walls and infinite floor/ceiling flats are a manifestation of a more severe form of the famous "moire" or "flash of black" error, which in early versions of DOOM kicked in even faster, in sectors in the mere several-hundred-units-tall range.

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Quasar said:

but at the utmost extremes weird things can still happen, just as they do on the horizontal plane near the +/-32000's.

Including the dreaded "Segmentation violation"? Honestly that's the worthy successor of "Visplane overflow" in terms of badass. I don't know how much it still happens in EE, but has been happening a lot with Boom, and other ports as well. It crashes/crashes where Doom was being tolerant, probably because of Doom.exe's lack of memory protection, as suggested in the EE readme file.

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hardcore_gamer said:

Care to be more tell us more? Whats psychedelic? Does it mean your game crashed or something?

The game didn't crash, but the color palette basically just went haywire. Just totally random colors everywhere. Though I did just try it in Chocolate Doom to see what would happen, and it just crashed.

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My first discovery with very deep pits was in E1M9 of Apocalyp, where you can jump down into a 16000 unit cavern (the fall is a bit less). The curious thing is that if you let yourself fall from the edge, you'll consistently get an R_MapPlane termination, but if you jump while running forward quickly, you'll make it safely to the bottom.

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Eh, in regards to the "deep shaft bug", the only source port I've really found a good use for it was in ZDaemon (I think it didn't work for me in ZDoom). I discovered it in my rocket jumping map when accelerating down a shaft using my rocket launcher. I was falling faster than I could normally fall, and it ended up "silent teleporting" me to the ceiling. Quite neat when it doesn't occur with any negative side effects or glitches.

I thought about putting bridge things near the top of the shaft, with a passageway out, that way you had to invoke the bug to get above the bridge things. :)

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Once I was messing around with a weapons mod and sv_fastweapons and fired off a string of rapid-fire explosives in that secret imp closet in map01, and I got shot into the tiny untextured space connecting the closet and the imp cage.

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Once I was Playing one of gggmork's levels (the really hard one where you are stick in this tiny circle surrounded by Commander Keens, and you have to kill 2 mancs with just a pistol, then cyberdemons and archviles etc etc.)

Now at one point in the level, I was killed by a manc.

And at the same time I died a voodoo doll picks up a megasphere.

So here I am, dead, but with 200 health and 200 armor.

And the really weird thing was that the monsters around me continued to shoot at me. Presumably because my health was not at 0.

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geekmarine said:

The game didn't crash, but the color palette basically just went haywire. Just totally random colors everywhere. Though I did just try it in Chocolate Doom to see what would happen, and it just crashed.


This can happen sometimes if Windows resets the pallete to the default Windows pallete after zDoom has set it's pallete.

Did it look something like this?

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Ah I know that one. Tho I think he does not mean anything Windows specific. I remember playing around with dehacked back in like 95 or so and giving the rocket -1000 damage.
When you then were shot by a Cyberdemon you still were alive and everything turned tutti-frutti.

Basically somehow the palette shifts I think.

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Setting projectile weapon speeds really high in dehacked. I was using Legacy back when i tried this but i beleive it's a Doom bug. If you set them over the "maximum" speed (35 i think) they become inaccurate. I set rockets to 1000 and they didn't even come from the gun barrel. A rocket would just appear at a random angle somewhere in front of me. Like you'd fire down a hallway and the rocket would come through the left wall halfway down, and explode on the right, or else pass through the wall entirely.

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Apparently only the first step is as long as the speed. Afterwards the speed is reset. Try with a projectile of speed 50 to 100 for example. Besides being inaccurate, it will come out of the gun at a farther distance from the barrel, then travel ahead as if 25 or 35 or however.

It seems to be unimportant if the described bug is specific to one wad, so let me shoot out my one: if you play Doom (vanilla) on -fast mode, save, then reload the game, sooner or later the game will hang. It seems to happen during notable events (things moving, monsters seeing or getting hurt etc. But not verified). If a sound is being played, it will enter the loop.

Fortunately, the nightmare! mode works bugfree here, even though technically it contains -fast (with reaction time nulling as well).

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udderdude said:

This can happen sometimes if Windows resets the pallete to the default Windows pallete after zDoom has set it's pallete.

Did it look something like this?


Hey, that's the description of my bug earlier!

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First I have a question, What monsters in doom attack each other?

Because while making an enemy closet in Doom builder i put in a baron of hell and 2 demons. when i opened it the baron of hell attacked me but the demons were trying to kill him. I've also seen a demon and a spectre fight before. Not sure if it's a bug or not but yeah, it was weird.

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Projectiles from enemies that are the same won't hurt each other. e.g. imp fireballs won't hurt other imps. But melee / hitscan enemies will attack each other of the same.

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Nixot said:

Projectiles from enemies that are the same won't hurt each other. e.g. imp fireballs won't hurt other imps. But melee / hitscan enemies will attack each other of the same.

its not bug. this protect monsters from killing his by other same monsters.
I saw some not aligned textures in plutonia 2 and small homs in "lost episode", but best collection of bugs is MOCK.

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This one isn't in Doom, but it's close. Go to map E5M8 of Heretic and kill all of the maulotaurs. When the columns lower, keep walking around but don't exit. If you look from one corner of the map to the far corner, there's a good chance that the whole map will go haywire, but not cause a visplane overflow error. The flats will become blinking solid colors and there will be all sorts of graphical glitches as you move around. I'm not sure about this, but if this happened in a non-boss map, the effect would continue between levels.

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In level 9 of Memento Mori 2, I got a massive HOM, becomimg blocked at the same time, about 4-5 times in about 500 tries (1% probability). I spent some time looking for the existing demos, and I found two.
mm2hom01: -skipsec 1450
mm2hom02: -complevel 4 -skipsec 4300


http://www.megaupload.com/?d=3IIKX3JU

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printz said:
Fortunately, the nightmare! mode works bugfree here, even though technically it contains -fast (with reaction time nulling as well).

Demos show a special varying value (bytes 05 and 06) for respawn and fast modes, both of which are set to 0 in nightmare. I'm not sure what those are for, but maybe there is a relation between them and the fact that nightmare may be exempt from this issue you're experiencing.

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udderdude said:

This can happen sometimes if Windows resets the pallete to the default Windows pallete after zDoom has set it's pallete.

Did it look something like this?

I'm not quoting Images, Dumbass.


That hurts the eyes.

Never happened in ZDoom for me, that has happened numerous times in Doom 95 though.

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