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Janizdreg

Monsters open locked doors

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I haven't seen any threads about this phenomenon yet, so here we go:

If only the front side of a door needs a key and the door can also be opened from the back side without a key, a monster can sometimes open these half-locked doors from the locked side.

This bug is utilized in the Doom II map27 speedrun, where an Arch-Vile opens the red key door. If you want to test the bug for yourself, try this wad.

I don't know much about the bug, but I'll tell you what I do know. For starters, the speed of a monster seems to define how thick half-locked doors it can open. In other words, the faster a monster is, the thicker doors it can open. For example, an Imp can open roughly 7 units thick doors and an Arch-Vile around 12 units thick doors. Another thing I've noticed is that none of the source ports fix this (at least none of those I've tried).

I'd like to know more about this bug, so if you have any knowledge or wild guesses on what this bug is about, please do share.

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You'll find some discussion stemming from the pacifist route on KS map23.

As that's quite a long thread, I'll give another link to a later relevant section.

I think it is fair to say that this trick idea is familiar to most experienced speedrunners, but unfortunately, not many mappers leave the possibility open. There's no real need for the "bug" to be fixed - if mappers don't want it to happen, they need only make both sides of the door require a key (or the far side not to be openable at all). After all, leaving the far side of a door openable without a key can lead to undesirable consequences even without the bug, if a monster can reach the door from the "correct" side. (There are a greater number of demos where that is exploited, though I couldn't list too many offhand - it's just not as memorable or remarkable a trick.)

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This is a well-known speedrunning trick (see here, thread at COMPET-N here). The most recent demo I know of that uses the bug is Grazza's MAP23 pacifist run (kp23-023.lmp) in the "Kama Sutra" demo pack. The thread about the demopack right here on DW contains some talk about the trick, too, as does a very recent thread on another topic.

I could pull more links out of my arse, but that'll do for now. :-)

EDIT: I should point out that I did make a test WAD to test this phenomenon, and found that, aside from Arch-Viles, only Demons, Spectres, Revenants and Cyberdemons can be made to open doors from the "wrong" side consistently.

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I agree that this doesn't really need to be fixed. Never the less I'd like to know more about this bug; especially what's causing it. Maybe someone who knows the source code can enlighten us...

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Kristian Ronge said:

EDIT: I should point out that I did make a test WAD to test this phenomenon, and found that, aside from Arch-Viles, only Demons, Spectres, Revenants and Cyberdemons can be made to open doors from the "wrong" side consistently.

I was just playing galaxia.wad on ZDoom yesterday and whenever I feel bored, I always have a tendency to summon friendly Pain Elementals and make them take out my foes with their unlimited supply of friendly Lost Souls. After the Elemental dies/takes out all foes, I summon a friendly Archvile to resurrect all dead foes since dead monsters resurrected by a friendly Archvile will also turn friendly. So my Archvile resurrected some Revenants and a dead Baron. Since all the enemies had already been killed, the guys were just roaming around while the Archvile kept resurrecting more monsters. I happened to see the resurrected Baron opening the Blue Door from the locked side and using the teleporter in the room.

So I am assuming Barons and Knights(they're not much different) can also open such doors. It could be different though, since friendly monsters have some unique properties.

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The key word in the sentence you quoted is "consistently". I never said no other monsters could ever open a door from the wrong side. During my examination of the phenomenon (which by no means was rigorous) the monsters I listed are the only ones that I could get to perform the trick. And they did it time and time again.

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... and things happening in zdoom shouldn't really be used as an indicator of what's possible in doom since zdoom's engine is very different.

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In DOOM/DOOM2 I have never ever witnessed monsters opening locked doors.

However, in the predecessors (Wolfensten3D/SOD) this was quite a common event in those instances where the floor-code-digits of both spaces being connected by the locked door are the same, and where there are no deaf-guard entities layed over those identical floor-code-digits.
If you've never built maps for Wolfenstein/SOD then this might seem alien to you, but it is a fact.

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Anders said:

... and things happening in zdoom shouldn't really be used as an indicator of what's possible in doom since zdoom's engine is very different.


True.

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