Experienced Points

Experienced Points
Next-gen AI and Next-gen BS

Shamus Young | 25 Mar 2014 19:00
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While strategy AI starts out stupid and requires a massive effort to make it do anything remotely stimulating, a combat-type AI has the opposite problem. It starts out godlike. The systems of a combat AI are incredibly simple and their goal is straightforward: "Shoot player with gun." The game already knows where you are, and doing the math to plot a line from the gun to the player's noggin is trivial. The fastest, easiest AI to write is one that headshots the player with pinpoint accuracy the instant they come into view, and keeps doing so until the player is dead. That also makes for an awful game, which is why designers generally don't stop there.

Unlike with a strategy-oriented AI, making the AI "good" in this case involves making it less efficient. We need to give this flawless killbot some human fallibility. We want it to miss sometimes, based on speed and distance. But we want it to miss the way a human would miss. We don't want it to just spray bullets randomly like its hands are vibrating. It should miss a lot at first, but eventually settle down and hit the target reliably as long as the target holds still. Because that's basically how humans shoot.

You have to apply this same sort of "simulated fallibility" to all the other parts of the AI: Detecting the player, tracking the player, choosing cover, and working with teammates. The question isn't "What is the most optimal action?" but "what is the most human-seeming action?"

So getting back to this "new generation" business: I have never seen a combat-type game where the AI required anything remotely special in the way of processing power. A lot of people (myself included) would probably say the original F.E.A.R. was the high-water mark (or very close to it) for squad-based AI combat. That ran fine on 2005 hardware, and even then I'm sure those wizard AI routines were barely a blip of the overall CPU usage. The AI required to decide whether to go up a ladder is peanuts compared to the power needed to animate the 3D model of the soldier doing the climbing.

Last year the pre-release hype for the new Thief promised that modern CPU power would make more advanced AI possible. This claim would be outrageous if it weren't so hilarious. It's like claiming that going to the gym will give you the muscles to carry around MP3 players loaded with more music than ever before. It's such a strange claim that you don't even know which part you're supposed to be arguing with. For the record, the "super AI" in the new Thief keeps track of how many times it's been spooked by noises or partial glimpses of the player, and if it gets spooked three times it will go aggressive and begin actively searching. It's an interesting gameplay addition and I approve of it, but that was completely possible using 1998 hardware. We're talking about a couple of bytes of memory and a few lines of code, here. Heck, I'm sure 1988 hardware would have been able to handle it.

Note that I'm not saying that good AI is easy to write. It's just that no matter how difficult it might be to develop, once the game is running the AI is not eating CPU cycles the way sound, animation, particles, or physics simulations are.

Whenever marketing tells you that we're going to need some brand-new technology to make the next generation of AI, they are probably suffering from some sort of truth deficiency. (They might not be lying. They might just be baffled by the technology and doing their best with what they know.) If we're talking about combat AI, then this is pretty much a guarantee. The one exception where they might be right is when we're playing a game with lots and lots of actors - perhaps battles with hundreds or thousands of participants. If the AI has to pilot a lot of ships or make large groups of people fight? Then yeah, that's going to cost you some processor cycles. Although it's also going to be animating all that stuff, so again it's likely the AI will still be a small portion of the overall cost.

You should probably just default to being extremely skeptical anytime someone says anything about horsepower near the start of a console generation. (Or if you're more of a PC player, then always.) Manufacturers need to sell these machines as fast as possible. Publishers want to sell you the game by telling you how awesome and advanced it is. Developers don't want to have to straddle multiple generations if they can help it. (Like developing for PS3 and PS4 at the same time.) Everyone has a reason to tell you that $500 purchase is justified and necessary. And if they can do so by making difficult-to-disprove technical claims? Then so much the better.

Shamus Young is the guy behind Twenty Sided, Spoiler Warning, and The Witch Watch.

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