The AI Systems of "Left 4 Dead" [pdf] • Hacker News Board

Re: The AI Systems of "Left 4 Dead" [pdf]

#71

Post by lotharbot » Wed, Apr 24, 2013, 7:05 PM UTC

solnyshok wrote: post #36

If a SurvivorBot ever gets far out of place for any reason, it is teleported near the team when no human is looking at it (AI cheating algoritm!!! Really enjoyed that)

One of the reasons for this is SurvivorBots, despite their relatively solid behavior overall, can occasionally get stuck on an obstacle or trying to decide between divergent priorities (follow the others or grab a powerup? They can get stuck in a "dancing loop" where they shuffle a couple steps one way and then the other.)

It's important in L4D to require players to pay attention to their teammates, but it's also important to maintain the "fun" aspects of the game. It's one thing if the AI gets behind because they're being attacked and the player is doing a bad job of protecting them; it's entirely different if the AI gets behind because its algorithm sometimes gets hung up (and it's not fun for the player to have to try to solve pathing glitches!)

Re: The AI Systems of "Left 4 Dead" [pdf]

#72

Post by err_badprocrast » Wed, Apr 24, 2013, 7:10 PM UTC

ahelwer wrote: post #68

afreak wrote: post #54

Earlier quoted context omitted.

> like TF2, it's not very playable unless everyone in the round is amenable to being a team player Amen. TF2 and L4D are two games that I consistently play years after the fact which is unlike other games I have. Unless you're playing with people you know, both games are equally frustrating. Specifically in TF2, it's those who go and play support classes when there are already enough of those in play on the map on yo…

That only matters if you care about winning. TF2 also has a huge accessibility problem which contributes to an overabundance of support class players, but also makes it a brilliant game. As opposed to the Battlefield series, where seeing the enemy first is most of the battle, it's actually difficult to inflict any damage at all in TF2. For instance, I'm at about the 200 hour mark and when I play demo I can only hit g…

Getting an airshot is harder at professional levels because by then they have an extremely good grasp of how to airstrafe - without that they'd be lit up instantly. It's actually easier to hit someone midair in general due to easily predicted trajectories; an easy trick to kill newbie scouts is to wait until they've burned jumps then take them out on the downward arc.

Once you have a lot of practice, it's amazing what you can do in TF2 - e.g. chaining 3 rocket jumps then taking out a sniper while still midair.

Better yet, a lot of mechanics like pyro reflect get much more interesting when you're facing other skilled opponents because of how much prediction is involved in the timing.

Re: The AI Systems of "Left 4 Dead" [pdf]

#73

Post by DerekAlia » Wed, Apr 24, 2013, 7:11 PM UTC

Brashman wrote: post #70

TheMakeA wrote: post #35

Valve is (was) very open with their publications. There are more available on their website[1]. I definitely recommend taking a little time to look through them. [1] http://www.valvesoftware.com/publications.html

Any idea why there hasn't been anything since 2009? Have they stopped publishing/presenting or just not updated the site?

too busy making money off steam.

Re: The AI Systems of "Left 4 Dead" [pdf]

#74

Post by angersock » Wed, Apr 24, 2013, 7:25 PM UTC

qznc wrote: post #69

Fargren wrote: post #61

Earlier quoted context omitted.

Quake III's AI not only receives but also gives commands by chat. If you enter a team full of bots, you can see them talk to each other and "plan" to a certain extent.

"Daemia patrol from quad to bfg for 3 minutes" ;) http://www.angelfire.com/linux/vmerchand/quake.htm

Hah! Quake 3 and UT99 both were helped immensely by having the ability to command bots--that often would be the difference between a stalemate in a CTF map and a flawless victory.

Re: The AI Systems of "Left 4 Dead" [pdf]

#75

Post by chc » Wed, Apr 24, 2013, 7:48 PM UTC

danso wrote: post #40

I love this game, one of the last FPSes I still play other than Team Fortress 2...unfortunately, like TF2, it's not very playable unless everyone in the round is amenable to being a team player. The multiplayer deathmatch allows one team to take the role of monsters, who have the backing of the zombie horde to make up for lack of guns. Playing it really provides some interesting insights to how the AI effectively fun…

The most inexplicable problem with the AI humans is that they absolutely guzzle adrenaline shots. Is there a needle anywhere around? Your adrenaline junkie teammate will grab it and shoot up immediately regardless of the situation. It's a huge waste of a great item. I initially thought it was just a bug, but as it was never fixed, I guess that's what they're meant to do. It's bizarre.

Re: The AI Systems of "Left 4 Dead" [pdf]

#76

Post by lelandbatey » Wed, Apr 24, 2013, 7:59 PM UTC

ahelwer wrote: post #68

afreak wrote: post #54

Earlier quoted context omitted.

> like TF2, it's not very playable unless everyone in the round is amenable to being a team player Amen. TF2 and L4D are two games that I consistently play years after the fact which is unlike other games I have. Unless you're playing with people you know, both games are equally frustrating. Specifically in TF2, it's those who go and play support classes when there are already enough of those in play on the map on yo…

That only matters if you care about winning. TF2 also has a huge accessibility problem which contributes to an overabundance of support class players, but also makes it a brilliant game. As opposed to the Battlefield series, where seeing the enemy first is most of the battle, it's actually difficult to inflict any damage at all in TF2. For instance, I'm at about the 200 hour mark and when I play demo I can only hit g…

I want to bring this up because it's a point very often overlooked about why TF2 is a fun game, and that is that it has a reliable and accessible in game VOIP system.

I don't see this talked about much, but it really makes TF2 shine as a straight up fun game. It allows players to communicate in any way they see fit, from the user casual to the highly formal/competitive. That means players can organize themselves to pull weird shenanigans or play very competitively using communication to gain an edge. Also, since voice is such a uniquely human attribute, it humanizes other players who would otherwise be anonymous participants.

The end result of this is that you get highly cohesive communities that make the game great!

Re: The AI Systems of "Left 4 Dead" [pdf]

#77

Post by mwctahoe » Wed, Apr 24, 2013, 8:31 PM UTC

lucb1e wrote: post #53

I never felt like playing this game until now. The AI sounds very interesting to try for myself! Game producers should release such documents upon launching the game, it makes it that much more interesting.

but then some people will look through the docs, find the exploits and become the top players. Wouldnt really be fair from a game play standpoint but I agree this was one of the most interesting things i have read in weeks.

Re: The AI Systems of "Left 4 Dead" [pdf]

#78

Post by Caskman » Wed, Apr 24, 2013, 8:45 PM UTC

Brashman wrote: post #70

TheMakeA wrote: post #35

Valve is (was) very open with their publications. There are more available on their website[1]. I definitely recommend taking a little time to look through them. [1] http://www.valvesoftware.com/publications.html

Any idea why there hasn't been anything since 2009? Have they stopped publishing/presenting or just not updated the site?

That's just an old page

http://www.valvesoftware.com/company/publications.html

Re: The AI Systems of "Left 4 Dead" [pdf]

#79

Post by krsunny » Wed, Apr 24, 2013, 10:37 PM UTC

lucb1e wrote: post #53

I never felt like playing this game until now. The AI sounds very interesting to try for myself! Game producers should release such documents upon launching the game, it makes it that much more interesting.

Its hard to find a good match these days, people will either kill you or themselves at the beginning of a PVP match.

Re: The AI Systems of "Left 4 Dead" [pdf]

#80

Post by Robadob » Thu, Apr 25, 2013, 1:08 AM UTC

solnyshok wrote: post #36

If a SurvivorBot ever gets far out of place for any reason, it is teleported near the team when no human is looking at it (AI cheating algoritm!!! Really enjoyed that)

There is a similar exploit people have used in survival maps. If you were are able to get your player physically stuck (usually by moving up and down an angled area which goes below your player height, e.g. stair rail with ceiling above) you would teleport to the nearest teammate. http://www.youtube.com/watch?v=m_TzVMFRO-c