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A Look At Modern Game AI
IEEE Spectrum is running a feature about the progress of game AI, and how it's helping to drive AI development in general. They explore several of the current avenues of research and look at potential solutions to some of the common problems.
"The trade-off between blind searching and employing specialized knowledge is a central topic in AI research. In video games, searching can be problematic because there are often vast sets of possible game states to consider and not much time and memory available to make the required calculations. One way to get around these hurdles is to work not on the actual game at hand but on a much-simplified version. Abstractions of this kind often make it practical to search far ahead through the many possible game states while assessing each of them according to some straightforward formula. If that can be done, a computer-operated character will appear as intelligent as a chess-playing program--although the bot's seemingly deft actions will, in fact, be guided by simple brute-force calculations."
I have to say that the AI in Far Cry 2 is definitely one of the worst of current generation video games. I couldn't play that game for more than a couple days before getting utterly bored and frustrated at the idiotic AI.
Enemy Territory: Quake Wars, on the other hand, has some of the best AI I've seen AND its a multiplayer game. The bots' ability to attack and defend objectives while using infantry and vehicle skills against the random actions of human players is incredible.
Since you used an example from a role playing game , I'll respond with similar. Disclaimer: I'm totally hot for genetic algorithms, ever since I saw this article on pathfinding.
Oftentimes, a player character's "best" moves are limited by other factors rather than just needing to push the button - does he have enough combo points? does he have enough mana? is he in range? and so forth, before it's even a valid choice. Using a more complicated getInformation set than is outlined in the pathfinding program linked above, let's lay out what the mob can find out:
How many hostile enemies are there? .. And so on - I'm sure there are more checks you could give the AI access to - probably even depending on its intelligence.
What kind of targets are the hostile enemies (ranged, melee, soft [rogue,mage,etc], hard [warrior,paladin])?
How hurt is each target?
How much damage has each available target done to me?
How much healing has each available target done to other hostiles?
How devastating have the non-damage abilities of available targets been to friendlies?
Which abilities are available to me?
Which status ailments do the available targets have currently?
Add up levels of opponents and levels of allies. Who is larger?
Which ability did I use last?
Then there are the actions the MOB can take:
Choose target (can target self)
Attack target (melee)
Attack target (ranged)
Use ability on target (repeat for however many abilities are available to the MOB - limited by mana, and so forth)
Run away
Close distance
Run to ranged distance
It would take quite a bit of training (you could probably automatically cull the first several generations, but later on you might actually have to interact with it yourself), but this kind of technique could end up with some very "smart" AIs that are fun and challenging to play against. You don't get God AIs, because they have limited information. You don't get God AIs, because their abilities are limited - and not by simple randomness. You might actually get an AI that stuns you and runs if it realizes it's outmatched, instead of stupidly sitting there and whaling at you with its rusty sword of crumbling.
Granted, genetic algorithms have some HUGE drawbacks:
The decision tree can be quite large, and it can take quite a few cycles to evaluate. Of course, as your fitness check you could check how long it took to execute.
It can take quite a bit of training (hundreds of generations, with thousands of entities each) before you get something that resembles an intelligent algorithm.
Meanwhile, it might generate something that checks for contingencies you never thought to bake into the AI script.