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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."
That is true. The computer is simply very different, so modeling our strengths is just as hard as our weaknesses.
It's trivial for an AI-controlled enemy to get headshots all the time. It's trivial for the AI to have complete knowledge of the battlefield and state of all items and characters on it. Humans can't do that.
It's a lot -less- than trivial for an AI to notice patterns in the enemy and exploit them. Thus the same approach tends to work 100 times against the same AI. It can't learn from its mistakes.
But then you end up with an AI that wins all the time
And we don't want that. We want an AI that wins some of the time, and that is beatable. That is, it should present us with a challenge, but the challenge can't be too great because then the game will be no fun.
So, we only want a smart-enough AI, not a god AI.
"Total destruction the only solution" - Bob Marley
The problem with game AI isn't that we can't make better AI, it is that we don't make it a priority. Todays machines are powerful enough to give us good visuals but not powerful or memory spacious enough to really devote resources to too much beyond that. In Mass Effect I want to say we devoted something like 75% of the memory budget to textures, and we still had to downgrade the textures before the final ship. I don't know what the final stats were, but I wouldn't be surprised if about 90% of the budget was allocated to textures and polygons.
That's not to say if you were to quadruple the memory on today's machines that AI would suddenly improve drastically, though. Many teams don't have the resources to devote to programming, so they need to take whatever is in the package. There's room for some entrepenureal spirits to create snap in AI programs, like what Havoc does for physics. Get started now, and you may have a refined product ready for the next generation of consoles.
As an animator, I just want to point out that most anything smart you see in a game is a scripted sequence. An AI marine flipping a table and taking cover is mostly animation work. The only real code there is is a simple set of conditions that determine if the animation should be played and then some state changes to coincide with the animation. The measure of an AI isn't what kind of cool things it can do, because that's animator work, it's how quickly it figures out what it should do, and how well it figures out the quickest way to do it. When you see AI running out in the open, taking the long route to cover, getting hung up on corners or doing circles, that's bad AI.
To give credit (and blame) where credit (and blame) is due, designers choose what kind of behaviors that are possible, so they too are highly responsible for the final appearance of the AI. If a designer neglects a cover system, then it can make even an intelligent AI look stupid by just having enemies stand in harms way. If a designer includes a visceral chainsaw attack, even a poor AI that gets a kill can still seem impressive.