Why game developers hate doors

I don't like to brag, but I've passed through many doors in my life and only occasionally made an error that resulted in either pain or embarrassment (and sometimes even both). Opening and closing doors is a very basic skill we all possess, but translating that whole process into a videogame? Not easy. At least, that's what hundreds of developers had to say yesterday when Stephan Hövelbrinks, the developer of Death Trash, opened up about the surprisingly difficult challenge of implementing basic doors in games.

The distress over the act of egress kicked off when Hövelbrinks shared a screenshot of his own Discord post in which he explains all of the complications that doors create in games. "Doors are complicated to have in games and have all sorts of possible bugs," Hövelbrinks wrote. "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."

It's easy to see how doors can exponentially complicate the logic of a game. Say an NPC in The Witcher 3 wants to turn in for the night. Without any doors to consider, all the AI has to do is map a route from the character's current position toward their bed. Throw a door or two in the way, though, and that NPC now needs to recognize there's a door in the way and have logic to control how it interacts with the door. But what happens if two NPCs use the same door at the same time? How does an NPC know whether a door opens toward or away from them? It's a problem so profoundly knotted that game designer Liz England, who has worked on games like Watch Dogs Legion and Sunset Overdrive, named it "The Door Problem."

In his tweet, Hövelbrinks claims that "AAA devs hate them" and even points out that the Assassin's Creed games solve the problem by pretending like doors were never invented in the first place (Valhalla, the most recent Assassin's Creed, does have some doors used in certain puzzles though). That tweet immediately went viral as game developers from all corners chimed in to talk about all the headaches caused by doors. 

"I don't exactly know how many man-months went into the door system in Control, but more than most abilities and weapons, for sure," explained Sergey Mohov, a lead gameplay designer at Remedy. Several of his peers jumped in to say that doors have always been an issue in Remedy's games.

In response to Hövelbrinks' tweet, Damion Schubert, a creative director at Boss Fight and former BioWare Austin developer, posted an entire thread dedicated to explaining the challenge of good videogame doors. 

Even The Last of Us 2's co-director said that doors are a waking nightmare. "IT WAS THE THING THAT TOOK THE LONGEST TO GET RIGHT WHAT WERE WE THINKING," wrote Kurt Margenau. Over several follow-up tweets, Margenau details the exhaustive process Naughty Dog went through to get doors working properly and the clever behind-the-scenes hacks required. For instance, when players are in combat situations doors will slam closed behind them automatically in order to impede enemies that might be chasing them, while in regular exploration all doors stay open to help players remember where they've been. 

Marcin Pieprzowski, who used to be a QA Lead on The Witcher 3, says that a boss fight in the prologue had a door that would lock and then unlock after players defeated a boss. During testing, the team found a whopping 12 different scenarios which would cause the door not to unlock, trapping the player. Pieprzowski says the fix was to just not lock the door in the first place. And then there's this hilarious story about how a quest bug accidentally opened every door in The Witcher 3—even the ones that were purely cosmetic and weren't supposed to go anywhere.

If you want to find more examples of how doors mess with games, the quote tweets to Hövelbrinks' original tweet are brimming with them. It just goes to show how often things in games that seem so brainless can end up being ridiculously complicated. So next time you open a door in a game, say a prayer of thanks to the poor developer who probably went bald trying to make it work.