L4D - AI Director

[Gaius Marius]

The concept of the AI Director in the latest Left 4 Dead game serie is, in my opinion, one of the best element to add recurring gaming in the latest year. It makes every game unique, it makes the game reactive to your performance and your actions.

I would like to know if mods have been made to modify it's behavior, if people have had the chance to peer into the related codings. What really interess me is how complex the Director's programming?

I got into thinking that games like Diablo 2, Titan Quest, or even Fallout 3 could benefit from such omniscient programming that determines your performance and throw unpredictable challenges at you in order to keep you on your toes and never bored.

Also, it would be a lot more fun to have the mobs do more than just "stand here and do nothing until the PC gets close"

[Gaius Marius]

So... nobody, eh?

[LordShotGun]

The AI director has already been ported to half life 2 and gary's mod but only because they share an engine with left 4 dead.

There is no way to port the Director to any other game engine without reprogramming it entirely, thus this topic is pointless.

[Gaius Marius]

The AI director has already been ported to half life 2 and gary's mod but only because they share an engine with left 4 dead.

There is no way to port the Director to any other game engine without reprogramming it entirely, thus this topic is pointless.

I don't necessarely want to port it. I want to see how complex and adapable an engine it is. Is it map-specific programming? Do you need to program it everytime Valve includes a new map? Can you create a new random spawnpoint and have it use this new element properly?

I am happy it has been integrated in HL2. Proof that it's not necessarely game-specific.

[LordShotGun]

I am happy it has been integrated in HL2. Proof that it's not necessarely game-specific.

No, but it is engine specific.

http://en.wikipedia.org/wiki/Left_4_Dead#AI_Director

Valve plans to implement it into their future games but currently it IS patented technology so screwing with it would be difficult as most of its secrets would be out of reach.

[blackfox]

So the thing about the Director is that asynchronous AI is hard to design and harder to program. Which is why it's Valve and not too many other people who put out stuff like this.

[Gaius Marius]

No, but it is engine specific.

http://en.wikipedia.org/wiki/Left_4_Dead#AI_Director

Valve plans to implement it into their future games but currently it IS patented technology so screwing with it would be difficult as most of its secrets would be out of reach.

I don't plan to break copyrights :smallwink:

Dynamic gameplay experience is, I believe, the holy grail of video gaming. AI Director goes a long way toward achieving that. So, I'd rather get to know the rationales behind its programming better.

Which is why I wanted to know if modding it was made possible.

[Arbitrarity]

It's moddable in-game to a limited extent, with a few script options available in console. Things like z_mob_spawn_min_interval_expert, and director_force_panic_event.

If you want a better feel for how the director works, try director_debug 1. It's supposed to give out a bunch of messages indicating the Director's "thought process". I haven't used it myself, I don't recall offhand exactly what it does though.

[ObadiahtheSlim]

Some things are hard coded. Like the weapon spawns. Sure it will be randomized a bit, but there are so many spawn points. Tanks and Witches are another. Once you play the maps enough times, you know where all the tanks and witches will spawn.

[blackfox]

Some things are hard coded. Like the weapon spawns. Sure it will be randomized a bit, but there are so many spawn points. Tanks and Witches are another. Once you play the maps enough times, you know where all the tanks and witches will spawn.To a limited extent. You'll remember the x possible spawn points per level. Karma is what ensures that they're right in front of the doorway everyone has to go through. The points are specific but they're not the same every time.

Arb, thanks for the tip, I'll have to try that sometime.

I'm fairly sure there are mods out there, but you'd probably have to do some digging to get them. The Director modding community has to be tiny...

[Science Officer]

For what it's worth, the AI director can also be used in Valve's free game, Alien Swarm.

[Draconi Redfir]

There actually aren’t any spawn points in any of the left 4 dead games. The director just automatically searches for places not in view by the survivors, and spawns the infected there. It's how custom maps are made available, and how you are able to play left 4 dead on team fortress 2 maps.

[blackfox]

There actually aren’t any spawn points in any of the left 4 dead games. The director just automatically searches for places not in view by the survivors, and spawns the infected there. It's how custom maps are made available, and how you are able to play left 4 dead on team fortress 2 maps.There are still some very specific spots where witches and tanks, in particular, spawn. Pretty sure that the Director plans witch/tanks far ahead enough that this is feasible. Example: Tanks always spawn at multiples of 25% progress in Versus, at least. Example: Witch in the safe room of Dark Carnival 4. Example: Witch right before the exploding barrier crescendo event in No Mercy ...3? Example: Tank 5 feet to the right out of the saferoom door.

[Arbitrarity]

Versus has a couple of special settings for the Director, forcing him to equalize spawn locations and item spawns. It's not exactly the same, but Tanks in versus always appear in ALMOST the same location for each team in a given round.
A lot of perceived "set location" spawns are usually actually serendipitous, though there are also elements of pacing and so forth built into the director making spawns in those areas more likely. Witches and tanks in particular are indeed "preplaced" quite far ahead.

[Lord of the Helms]

Some things are hard coded. Like the weapon spawns. Sure it will be randomized a bit, but there are so many spawn points. Tanks and Witches are another. Once you play the maps enough times, you know where all the tanks and witches will spawn.

Well, at best, you can know all the possible places where Tanks and Witches could spawn, but there's several different such locations in almost every level where it could happen, so you can't actually be sure which of the points they'll spawn at on any given playthrough.

[Acanous]

the director seems to lack any measure for dealing with speed runners. If you can get through all of no mercy in 15 minutes or less? You're not even going to SEE any zombies past the safe room exits. Probably won't see any witches, either-- and special infected? On your first couple tries, the Director will try slowing you down with hunters and smokers, but once you learn how to headshot them on the run.. the game actually starts to get boring. It's like finding the perfect solution. The man behind the curtain is exposed and you move on to another game.

[warty goblin]

the director seems to lack any measure for dealing with speed runners. If you can get through all of no mercy in 15 minutes or less? You're not even going to SEE any zombies past the safe room exits. Probably won't see any witches, either-- and special infected? On your first couple tries, the Director will try slowing you down with hunters and smokers, but once you learn how to headshot them on the run.. the game actually starts to get boring. It's like finding the perfect solution. The man behind the curtain is exposed and you move on to another game.

If you don't find playing that way fun, don't play that way.

[Worira]

The thing is, it's also the best strategy in multiplayer, and the infected can't really do anything to counter it.

[Gaius Marius]

The thing is, it's also the best strategy in multiplayer, and the infected can't really do anything to counter it.

Ergo, it's realist. When facing zombies, keep running.

[warty goblin]

The thing is, it's also the best strategy in multiplayer, and the infected can't really do anything to counter it.

I'm a firm believer in the following principle:


The best strategy in any game is the one which maximizes fun for all participants.

Winning or losing is thus relevant only to the extent it improves the fun had, but should not, a priori, be the primary consideration. In this case if given the choice between certainly winning via a cheap and boring exploit, or maybe winning via the actually fun gameplay, I hold that it is foolish to adopt the former strategy since that way nobody's having fun. And isn't that the reason we play games like L4D in the first place?

[Acanous]

Well, for me the concept behind a survival horror game is to well... Survive the Horror.
In Coop mode, I still play with others, and must slow down because not everyone knows how to speed run- but this can become grating, as you encounter difficulty you know you could have easilly bypassed, which means the other players are lowering your chances of survival. This is somewhat immersion breaking, as in any survival scenerio where you're grouped with strangers, straggling behind is going to get you left behind to die and maybe hold off the bad guys while the rest of the group makes tracks.

In VS mode, if you're not speed running, you're both holding back your team, and slighting your opponents by not playing at your best.

When the game was first released, Valve knew people would attempt this tactic- playtesting showed that players would just try running through. Thus the "Hits slow you down" mechanic. They added Smokers and Hunters to further deter you from running off on your own, and THEN threw in added rushes in the Director for players who take off running.
But the zombies are too slow, and the director can't keep up.

I see this not as a problem of "Slow down and have fun" and more of "I need a game that keeps up with me, so I can have fun while playing at my best".

L4D2 did that for a while, with the forced stops and endless rushes. Still, play through a few times, you learn the tricks and it stops evolving.

[Treayn]

Really, the director is only as dynamic as the maps; that's the limiting factor. Now, if there was a way to randomly generate maps...

As for runners, the director should really throw more and more zombies and specials at you, proportionate to the distance away from your teammates you are. Also, there needs to be more variety in crescendo events.


I also think something's gone missing when they moved from L4D1 to 2. The atmosphere, the level design, the specials. Boomers and Hunters have seen to have lost a lot of their edge from the first game, now superseded by Chargers and Spitters. Not saying they're useless, just that Chargers and Spitters provide more utility.

Hunters seem to pounce slower, and seem to have a delay between pounces. It also certainly feels easier to be melee'd as a hunter.
Boomers seem even more fragile from the first game, and their vomit range seems shorter.

The flatter, lower, more open level design certainly doesn't help the hunter and his old 25 pounces, nor does it help the boomer find good close-quarters ambush spots. It also doesn't help that boomer vomit in daytime levels isn't too hard to see through.

[Kita Markus]

In theory, Valve could make the director spawn things other than equipment and AI.

The Director can already adapt to any map, she could start getting more advanced.