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Why is this a bug? I suppose it could be a mapping error. Presumably the linedef type for the rear of the door is a normal "open me". So, the monster tries to open it, to get towards the player... and it opens! That is what I would expect. Am I mis-interpreting this? If not, it might be a good idea to cite and wikilink some levels where this happens. -- Jdowland 21:10, 3 Jan 2006 (UTC)

Definitely sounds like mapping errors to me. -- TheDarkArchon 22:22, 3 Jan 2006 (UTC)
It appears to be a rather common misconception that monsters can open locked doors due to a bug in the engine. Perhaps the article should reflect this fact. 81.231.137.101 22:34, 3 Jan 2006 (UTC)
Done -- TheDarkArchon 11:43, 4 Jan 2006 (UTC)
It's not a misconception, the bug really exists. See this wad. Janizdreg 11:37, 22 January 2006 (UTC)
All I can see is that the door in the wad is not locked on the other side. Fredrik 12:34, 22 January 2006 (UTC)
A map author could want it to be that way, say to create an area you can get into but can't get out of (without a key), which is why I wouldn't call this a mapping error. Janizdreg 15:03, 22 January 2006 (UTC)
If the demon's radius is such that it is overlapping the door sector, it is a mapping bug. I haven't been able to determine this via doom builder. What's the purpose of the sector that the demon is inside, btw? -- Jdowland 15:13, 22 January 2006 (UTC)
The demon's radius isn't overlapping the door. Monsters can also open locked doors by walking to them, not only by starting inside them. If you want to see this in practice, try this wad (in the map you just need to fire a weapon to alert a demon in the next room and wait for the demon to open the door).
And to answer your question, the 3 linedefs around the demon are monster blocking and are there simply to prevent it from moving around in the room. Janizdreg 18:58, 23 January 2006 (UTC)
Hmm weird. How does that demon open it up - is the thing clipping over the edge of the door sector? -- Jdowland 14:20, 22 January 2006 (UTC)
Probably. It seems that the monsters' clipping is pretty rough at times, especially if the monster is fast (increasing a monster's speed seems to improve its ability to open these half-locked doors, or in other words, the faster a monster is, the thicker half-locked doors it can open). Janizdreg 18:58, 23 January 2006 (UTC)

Only one one-way lock in commercial IWADs?[]

Correct me if I'm wrong, but I thought I saw another of these in E2M6: Halls of the Damned. Yellow key room.

You are correct. I changed the article accordingly. -- Janizdreg 01:06, 21 July 2007 (UTC)
I was going to add that one, but only after looking up how thick the door was.  Correct me if I'm wrong, but there aren't actually any monsters nearby who can open it from the locked side.    Ryan W 03:29, 21 July 2007 (UTC)
The demons in the room can open it, though you basically have to push them against the door by shooting/punching them. Even then it's pretty pointless since you can get the key for the door from the very same room :P Still, I believe the door should be mentioned in the article. -- Janizdreg 14:14, 21 July 2007 (UTC)
I agree.    Ryan W 20:34, 22 July 2007 (UTC)

I have just observed this in the rocket launcher room of E2M2.  (The door is 8 units thick, but of course there are Demons about, even on the low skill levels.)  Diana save us.    Ryan W 19:54, 7 September 2007 (UTC)

Actually, it seems both yellow key doors in the level are like this. -- Janizdreg 22:09, 7 September 2007 (UTC)
Fair point, although to get it to happen at the chaingun room would be a more contrived situation IMHO.    Ryan W 23:20, 7 September 2007 (UTC)
which is why the bug can only rarely be witnessed   As far as id's levels are concerned, another reason is that all the vertexes seem to be on an 8x8 grid, which means it takes a little work to make a door less than 8 units thick!    Ryan W 11:33, 17 September 2007 (UTC)
This is a bug. The thing is that monsters can open the locked door FROM THE SIDE THAT IT'S LOCKED FROM. This is very similar to a 'grab' (AKA Plasma Bump Bug). The problem is that if the monster is fast enough (and the door is thin enough), the monster can reach the other side of the door and inadvertently open it. This is a very useful exploit for speedruns on Monster Condo. -Wagi
Um... yes, which is why all those facts are already included in this article and in the MAP27 article.    Ryan W 22:51, 9 November 2007 (UTC)
Not really. The MAP27 article gives very breif description of the bug, a mere mention at best. It nowhere near explains half of those things I just said. -Wagi
The detailed description of the bug belongs in the bug article, not in the map article. The MAP27 article describes the phenomenon in enough detail and offers a link to the detailed bug article, so I think it's fine the way it is right now. -- Janizdreg 18:15, 12 November 2007 (UTC)
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