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[TheZorg]

I still remember playing F.E.A.R. for the first time (back in... 2005?) and literally falling on my ass when a saw an enemy tipping over some bookshelves to create cover. Heck, the last game that had blown my mind like that in terms of AI was Half-Life.

Nowadays this is just standard behavior for any AAA game NPCs, but why only in 3D games? Actually, I'm not really counting top-down 2D, and I'm only considering action titles, but correct me if I'm wrong: is there any 2D sidescroller you can think of where AI is challenging/a big factor in the game?

I find it weird that no one, or very few people, has tried to "port" advanced 3D AI techniques to sidescrollers. Of course I can think of a lot of limiting factors: for example, how could you have such a concept as "cover" in 2D? Blackthorne did it, and it had basic line of sight too, but combat wasn't in general very dynamic. But what about squad behavior? Fleeing from combat? Using the environment to counter the player's attacks? Hell, are most sidescroller NPCs even aware of each other?

So my question is, first of all, am I wrong? Did I just totally miss some awesome sidescrolling AI?
Second of all, what do you guys think? Would it be interesting to see some higher class AI in sidescrolling games?
And finally, is it possible? Or is there an insurmountable limitation to implementing AI in sidescrollers?
I personally think that not only it is possible, but that the result would be really interesting... Let's see what you think  

[Contrary]

Though I've never played it, personally.

[Triplefox]

More sophisticated AI has been done here and there, mostly with "2D deathmatch" type games - there's also the "Infinite Mario Bros." AI contest for a good example of straight-up AI-driven platforming. There are some things making it a different _technical_ problem from the 3D AI case.

First of all, animation-wise, 2D side-scrollers have to deal with sprite alignment issues. In 3D games you get model alignment issues, but a lot can be done algorithmically to position bones in the right places while giving the anim and environment designers some freedom. In 2D you don't get this until you move to skeletal anims, and that forces your art style towards the paper-cutout look. With sprite sheets you will probably have to restrict motions or allow large visible errors.

Secondly, side-scrollers naturally contain tons and tons of platforms, while 3D games tend towards a world that is mostly flat or sloped surfaces. AIs that can automatically traverse complex platforming situations(e.g. multiple moving platformers + obstacles) are a mostly undeveloped area, because in those situations, the platforming itself is providing sufficient challenge to the player. The challenge of the AI isn't going to change what the player is doing; it's another obstacle, and it has a more complex and nuanced pattern, but unless you slow down the physics so much that you can plan ahead like in a cover shooter, the nuances are going to go unseen. At that kind of slow speed, you could probably come up with another genre of platforming, but nobody AFAIK has really investigated that design path. I'd like to, someday.

Alternately, the game might be something like Transformice only with bots instead of people, and they try to travel across the level as well as possible, given the available tools. A "smart Lemmings." That could be interesting.

[Defsan]

Yes it does o_o

@TheZorg: It certainly has some limitations, but the lack of third dimension can be an advantage because it may make things simpler. You still have to worry about ducking, peeking to see the the player's position, preserving ammo, running away and hiding; but you'll only have to worry about if the AI character does it forward or backward, up or down.
Come to think of it, hiding in a 2D platformer wouldn't be too effective unless you had an active FOV or something. Otherwise you'll always see an enemy, even if it's hiding behind cover.
In short, it's possible but it has its own series of problems that don't happen with 3D (as Triplefox said) but it also has its own series of advantages (mostly simplicity I guess) that 3D doesn't have.

[J-Snake]

Good thread. One of my upcoming 2D-projects is featuring advanced A.I. It is a rethought of Mega Man, Shinobi, Ninja Senki(nice little project, Pixeltao:)), final Ninja (flash-game) and stuff like that. The game will combine closed combat, distant combat, stealth and some traverse-puzzles in one (multiplayer matches also important:)). Project-Name is "AGENT X".  The advanced A.I will be used for some bosses, also certain enemies will be aware of their environment and they will behave in a believable way. It is true, platformer A.I. can be the most complex one since it needs a sense for its acrobatical capabilities (a 3D- shooter doesn't need it since movement in all directions can be treated equally) to traverse platforms but I found ways how to deal with it. I have no definite order for next projects but it is likely that I will start working on it at the end of the year. Currently I am working on "TrapThem" that I intend to release in summer.

[J-Snake]

I think there are 2 main reasons why advanced A.I. is not featured in platformers:

1. Platformers were invented in the old days. The hardware was weak and advanced A.I. can always be technically complex to implement.

2. What made Mega Man so great is its "patternised" gameplay. Especially  the bosses had some simple but challenging action-patterns. The process of figuring them out and adapt to them was the fun part.  

Now if you add advanced A.I. the patterns can get so complex that an ordinary human won't be able to recognize them anymore. So you have to seriously consider how to add A.I. But on the other hand advanced A.I. can add a new element in platformer game-design: It doesn't need to be only adapting to existing patterns anymore but you can "provoke" new patterns!. Since advanced A.I can adapt to your actions you can control it, it means that in some ways you are able to change the patterns of the A.I. The process of doing so can be interesting and fun. For the game-designer on the other hand it can be very difficult to provide the player enough  possibilities how to deal with the A.I and keep it challenging but fun without being cheap at the same time.

But I am confident that it is possible to make a decent and very rewarding gaming- experience with advanced platformer-A.I. We just don't have to exaggerate with it.

[Trent]

Come to think of it, hiding in a 2D platformer wouldn't be too effective unless you had an active FOV or something. Otherwise you'll always see an enemy, even if it's hiding behind cover.

My current project is a 2.5D platformer with focus on lighting. If an enemy is in a dark area, hiding behind boxes can be fairly beneficial for him. 

As far as making them 'advanced', all I've done is add A* and some raycasts / sensors to determine if the enemy should try to jump across a gap. For the most part they'll make it, but if they don't, it's pretty funny to watch them fall into a pit.

They can't all be geniuses. 

[J-Snake]

Cool, any vids?

[Trent]

Nothing recent. The game has been redesigned to work with an in-game level editor, so things have been moving a bit slowly. 

Have a few videos on youtube, but they're pretty outdated. The game went from an egyptian platform puzzler to a zombie shooter. 

http://www.youtube.com/user/MTOMalley

[eobet]

GODS from the Bitmap Brothers was supposed to have it according to the PR hype, but I don't think it really showed in the game (perhaps apart from the thief character).

[Dustin Smith]

Play games by Tomomi Sakae, namely Mr. Gimmick and Trip World. Those titles have superb enemy ai, and further -- for me at least -- the sense of connectedness to their worlds.

[J-Snake]

Cool, thanks, will check them out. Now I know where you come from;)

[BilbyCoder]

I only played the first few levels but the skeletons in Trine, but the Skeletons seemed to behave disturbingly competent in navigating the platforms to get to you.  From memory though ranged zombies still had an unfortunate habit of shooting the platform ledge below.

If I can get some enemies to move like those skeletons in my game I will be a very happy person.

Kieren

[SirNiko]

Imagine you had the world's best enemy AI in a platformer. What would that game be like?

I'm having trouble imagining anything other than lakitu dropping spinies in a neat row on the far side of a pit, so you have to jump on them.

If you need enemies to navigate platforms, the easiest way is to just hard code them to know the most efficient path up, with exceptions built in to avoid blocked paths.

Or maybe a game where the goombas and troopas are all played by humans, and the game mimics the behavior of the players that win the most?

[Fallsburg]

Imagine you had the world's best enemy AI in a platformer. What would that game be like?

I'm having trouble imagining anything other than lakitu dropping spinies in a neat row on the far side of a pit, so you have to jump on them.

If you need enemies to navigate platforms, the easiest way is to just hard code them to know the most efficient path up, with exceptions built in to avoid blocked paths.

Or maybe a game where the goombas and troopas are all played by humans, and the game mimics the behavior of the players that win the most?

See

.  Just because something is a platformer, doesn't mean it has to be Mario.

Also, hard code them? Have you ever done pathfinding of any kind? Because saying hard code them, I would find it hard to believe that you have.  And what if you wanted to procedurally generate your environment?  Hard coding would literally be impossible.

[teomat]

Seeing this topic made me think about Cobalt, specifically the end of

where the bots push the bomb back inside that bunker.

Now I don't think we know enough about it yet to tell if that isn't just a funny coincidence, but it sure looks cool.

[sampah43]

Seems that almost no one is talking about the platformer AI in Fortune Summoners (http://www.youtube.com/results?search_query=fortune+summoners  or official site in Japanese http://www.junglejapan.com/products/game/lizsoft/fs/index.php) -- they are very good, not only because they follow you wherever you go, but also assist you fighting the enemies along the way, including using spells and dodging both enemy attacks and platform traps!

This is indeed an advanced platformer AI. Any other games come close to this?