The Door Problem
March 11, 2021 12:24 AM   Subscribe

Doors are complicated to have in games and have all sorts of possible bugs. Mostly because they're a dynamic funnel and block in the pathfinding, potentially locked, potentially destructible, but in general because they sit potentially between any game interaction or character to character situation from here to there. [twitter thread] posted by Pyrogenesis (28 comments total) 9 users marked this as a favorite
 
Red Dead Redemption 2 does doors well. Probably burned 20% of the budget on them.
posted by GallonOfAlan at 1:05 AM on March 11, 2021 [2 favorites]


When we were living in Colorado there was snowfall. Our cat — I'm a cat man — wanted to get out of the house so I opened a door for him but he wouldn't leave. Just kept on crying. He'd seen snow before and I couldn't understand it. I kept opening other doors for him and he still wouldn't leave. Then Ginny said, 'Oh, he's looking for a door into summer.' I threw up my hands, told her not to say another word, and wrote the novel The Door Into Summer in 13 days. -via
posted by fairmettle at 2:09 AM on March 11, 2021 [28 favorites]


We're all looking for a door into summer 😭
posted by Foci for Analysis at 3:22 AM on March 11, 2021 [8 favorites]


AAA devs hate them too.

Do AAA devs have the time to hate them?
posted by Cardinal Fang at 3:29 AM on March 11, 2021


I once had a Sims character die, because there was only one door, it was being blocked by a non-player character who wanted to come in, and they couldn't possibly pass by each other.

And this is why all bathrooms must have two doors or you will die.*

* If you are a first generation Sim.
posted by jb at 4:38 AM on March 11, 2021 [12 favorites]


Once upon a time I had the time to beta test Interactive Fiction text only games prior to IF comp. I stumbled onto the idea to try 'SIT ON DOOR' for a particular game, which broke it spectacularly. It somehow made a new room object that I couldn't leave, because it was the door and thus wasn't connected to any doors. I don't even know how that error was possible, but yeah, games don't even need to have graphics to have doors be a problem.
posted by cobaltnine at 5:41 AM on March 11, 2021 [19 favorites]


I used to be on the staff of a text-based MMO. There were simple room connections (go east, climb up etc.) and then there were doors. A door is just a type of object with a reference to another room, and few other important flags and fields...

One of those important flags marks it as immobile, so characters can't pick it up.

While it's pretty cool to own a door that leads right to the heart of the main city, it's a lot less fun to be stuck inside the bank when someone steals the only exit, puts it in their backpack and then (somehow) casually strides through it, taking it with them.
posted by Foosnark at 6:17 AM on March 11, 2021 [10 favorites]


Finally played Fallout New Vegas during the pandemic (I like my games old) and getting slowly smashed into the wall by the door you're opening is a total mood.
posted by es_de_bah at 6:25 AM on March 11, 2021 [10 favorites]


I once had a Sims character die, because there was only one door, it was being blocked by a non-player character who wanted to come in, and they couldn't possibly pass by each other.


Slight derail, but this is actually a classic problem in computer science! The underlying issue is known as the dining philosophers problem, and solving it turns out to be super tricky for cases like this--you need to simulate cooperation, but making multiple objects "talk" to each other for stuff like this is phenomenally complicated, so most times you just make everything optimize for itself, and hope no one notices when seemingly-simple problems lock everything up. Like late-stage capitalism!
posted by Mayor West at 6:30 AM on March 11, 2021 [16 favorites]


Just to observe that this is not entirely a problem related to the digital realm: on one of our regular evenings playing our GURPs campaign (like D&D but differently complicated), one player and the GM got conversationally stuck for 15 minutes on a debate/derivation from first principles on whether the doors of mountains cabins always opened outwards or inwards*.

The two sims who died, unable to pass together through one door, turns out to be a very apt metaphor for certain personalities.

* the logjam was finally cleared when, as one of them started a new attack on the problem, I bellowed "OH. MY. GOD." to the relief of the other players.
posted by fatbird at 6:48 AM on March 11, 2021 [4 favorites]


How did the Sim die because of the blocked door? Did B it starve, get crushed, or something else?
posted by Going To Maine at 7:06 AM on March 11, 2021




Anger Foot solves the door problem very well.
posted by Reyturner at 7:49 AM on March 11, 2021 [2 favorites]


How did the Sim die because of the blocked door?

Starved, because neither had the wits nor the code, as they faced each other in the doorway, to hold an impromptu election for who would go first.

Or maybe the Canadian version, where an endless loop of "no, after you" leaves them deadlocked. Same end, either way.
posted by fatbird at 8:45 AM on March 11, 2021 [5 favorites]


Oh, dear, doors.

I remember hating a LOT of games because to simulate buildings, they have to put in a TON of doors, but most of them do NOT open. I have to learn to read the texture map on the door... Type 1 does open, type 2 does not. FPS, of course.

And a lot of games simply do NOT implement doors. Go up to a door and open it, but you don't actually walk through that door. What they really do is they show an animation of you walking through, but in reality they are loading the next level and teleporting you from one room to another.

You will notice this especially in the levels in Mad Max or Tomb Raider when you "squeeze through a narrow opening". That's not a passage/door... It's a level transition.
posted by kschang at 9:14 AM on March 11, 2021 [3 favorites]


I can personally confirm that programming doors suck. The implementation I worked on was simplified so avoided about half the problems in that gamasutra list, but also had to work in a predicted multiplayer game so added another 12 problems. And we got into situations where one player saw the door as closed and the other saw it as opened which made everyone angry. I'm definitely anti-door now
posted by JZig at 9:19 AM on March 11, 2021


Some of the most memorable video game doors I can think of are the PS1 Resident Evil series and those in the Amnesia series, which fall on completely opposite sides of the interaction spectrum but serve to increase tension. RE's doors just hid loading the next room behind a first-person animation leading into darkness, building tension since there's no way to know if a zombie is lurking just on the other side. Amnesia allows fully dynamic doors, letting players peek through a crack, and then slam it shut if there's a shambling monstrosity just beyond.

Doors are so difficult to get right and need to behave very differently for different kinds of games. Oddly, they're often more dangerous and difficult to implement than guns.
posted by subocoyne at 9:33 AM on March 11, 2021 [1 favorite]


Most of the implementations only mention open and closed states - of course that’s hard enough - because think how hard to model when a door is not a door BECAUSE IT’S AJAR.
posted by clew at 9:58 AM on March 11, 2021 [4 favorites]


Other fun game dev stories include the "mirrors" in Duke Nukem 3D that were duplicates of the rooms laid out in reverse, as well as fun implementation details like the "invisible bunnies" that power World of Warcraft and the "train hats" of Fallout.

While looking for those supporting links, I ran across this twitter thread of other fun gaming hacks, which seems like a near infinite topic considering the time pressure and need to work around game engine issues.
posted by autopilot at 10:46 AM on March 11, 2021 [1 favorite]


It’s not only computers which struggle to compute with doorways.
posted by fantabulous timewaster at 10:59 AM on March 11, 2021 [1 favorite]


one player and the GM got conversationally stuck for 15 minutes on a debate/derivation from first principles on whether the doors of mountains cabins always opened outwards or inwards*.

Clearly the answer is inwards so that a Bar will lock the door.
posted by Ultracrepidarian at 11:03 AM on March 11, 2021 [4 favorites]


Also so that a heavy snowdrift won't trap you inside.
posted by rifflesby at 11:09 AM on March 11, 2021 [3 favorites]


Why wouldn't a bar work for doors that open outwards? As for snowdrift, fair point, but (a) that's why you have a porch; and (b) you could exit through a window. And not everybody lives in a region subject to snow.

But on further consideration, old–timey cabin doors probably do open inwards, because leather hinges would rot faster if they were outside.
posted by Joe in Australia at 1:33 PM on March 11, 2021 [1 favorite]


Why wouldn't a bar work for doors that open outwards?

For the Door bar it would depend on where you mounted the brackets that hold the bar. If the door goes in, the brackets have to be on the house. If outwards they have to be mounted to the door itself. I think generally the brackets attach to the frame for more secure attachment.
posted by Ultracrepidarian at 2:56 PM on March 11, 2021 [2 favorites]


Outside doors open inwards so people can’t pull the pins and break in. Doubly so for isolated cabins. Ask me how I know. On second thought, don’t. Fixing doors on isolated cabins that people have busted open is a pain in the arse.
posted by fimbulvetr at 4:04 PM on March 11, 2021 [2 favorites]


Outside doors open inwards so people can’t pull the pins and break in.

You can get security hinges to protect against this. I learned about these following a link somewhere in a package stealing thread a few weeks ago.
posted by paper chromatographologist at 4:11 PM on March 11, 2021


The Dead Space series has the greatest video game doors, purely for the sound design. It’s this high-pitched whiiine-CLANG! that just put me on edge every time I entered a room.
posted by FallibleHuman at 5:22 PM on March 11, 2021


OH.MY.GOD.
posted by fatbird at 10:38 AM on March 12, 2021 [4 favorites]


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