My Secret Life as a Spaghetti Coder
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Dave Mark raises some interesting questions about artificial intelligence in games over at AIGameDev.com. First, he explains that although we're seeing more and better AI in games, a common complaint heard from gamers runs along the lines of "why can't they combine such and such AI feature from game X in game Y." Then, Dave poses the questions for developers to answer:
We can only cite limited technological resources for so long.
...
Perhaps, from a non-business standpoint... that of simply an AI developer, we should be asking ourselves what the challenges are in bringing all the top AI techniques together into the massive game environments that are so en vogue. What is the bottleneck? Is it money? Time? Hardware? Technology? Unwillingness? Unimaginativeness? A belief that those features are not wanted by the gamer? Or is it simply fear on the part of AI programmers to undertake those steps necessary to put that much life into such a massive world?
Let me first admit that I'd wager Dave Mark knows a lot more about this stuff than me. That's how he makes a living, after all. My experience in developing game AI comes from choose your-own-adventure text-based games as a kid (where the algorithm was very deterministic, with few options), making villagers walk around in Jamaicanmon!,



and making spaceships run away from you instead of seeking you out in Nebulus: Ozone Riders.



I even asked Glitch, Wes, and Jonathan (teammates on the project) to remind me of some simple vector math and draw it out on the wet erase board for Nebulus. And I still made them go the wrong direction (which ended up being pretty cool, actually).

In other words, I haven't had much experience with AI as it's typically implemented in games, and what little experience I have had is limited to things I wouldn't (personally) classify as AI to begin with.

Still, I have had some experience in what I might call "classical" AI (perhaps "academic" is a better term). Stuart Russell and Peter Norvig wrote the Microsoft of books on Artificial Intelligence (90% market share for AI textbooks), and I've read through a fair bit of it. I've implemented a couple of algorithms, but mostly I've just been introduced to concepts and skimmed the algorithms. In addition, I've been through Ethem Alpaydin's book, Introduction to Machine Learning, which would have comparatively fewer ideas applicable to games.

I guess what I'm trying to say is: although I have some knowledge of AI, consider the fact that Dave's experience dwarfs my own when I disagree with him here: It is precisely the fact that we don't have enough processing power that gets in the way of more realistic AI in our games. Or, put more accurately, the problems we're trying to solve are intractable, and we've yet to find ways to fake all of them.

I'm not convinced you can separate the failures of AI from the intractability of the problems, or the inability to design and implement a machine to run nondeterministic algorithms for those problems in NP.

Compared to deciding how to act in life, deciding how to act in Chess is infinitely more simple: there are a finite set of states, and if you had the time, you could plot each of the states and decide which move gets you the "closest" (for some definition of close) to where you'd like to be N moves from the decision point. Ideally N would get you to the end, but even for Chess, our ability is limited to look ahead only a small number of moves. Luckily for Deep Blue (and others), it turns out that's enough to beat the best humans in the world.

Even though Chess is a complex problem whose number of game states prevent us from modeling the entire thing and deciding it, we can cheat and model fewer states - when we can make an informed decision that a particular path of the decision tree will not be followed, we can forgo computation of those nodes. Still yet, the problem will be huge.

There are other ways of "faking" answers to the AI problems that face us in development. Approximation algorithms can get us close to the optimal solutions - but not necessarily all the way there. In these cases, we might notice the computer doing stupid things. We can tweak it - and we can make special case after special case when we notice undesired behavior. But we are limited in the balance between human-like and rational. Humans are not rational, but our programs (often) are made to be.

Presumably, they give the policeman in GTA 4 a series of inputs and a decision mechanism, and he's thinking purely rationally: so sometimes the most rational thing for him to do based on the decision model we gave him is to run around the front of the car when he's being shot at. Sometimes he jumps off buildings. (Video via Sharing the Sandbox: Can We Improve on GTA's Playmates?)



It may not be smart, but it is rational given the model we programmed.

You can make the decision model more complex, or you can program special cases. At some point, development time runs dry or computational complexity gets too high. Either way, game AI sucks because the problems we're trying to solve have huge lower bounds for time and space complexity, and that requires us to hack around it given the time and equipment we have available. The problems usually win that battle.

Pac-man game screen shot Game AI has come a long way since Pacman's cologne (or maybe he just stunk), and it will get better, especially as we move more gaming super-powerful servers. Still, it's far from ideal at the moment.

What do you have to say? (Especially the gamer geeks: programmers or players)


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Since the gift buying season is officially upon us, I thought I'd pitch in to the rampant consumerism and list some of the toys I've had a chance to play with this year that would mean fun and learning for the programmer in your life. Plus, the thought of it sounded fun. Here they are, in no particular order other than the one in which I thought of them this morning: More...


Yesterday I wrote about how Microsoft's XNA framework lowers the barriers you have to cross to make games. Today, I made a little screencast of my game, Jamaicanmon:



I only had WMV format readily available to me at a decent size, so I uploaded it to YouTube. If you'd like to see it better in a slightly larger version (~5MB), you can download the Jamaicanmon Preintroduction WMV.


Like many of you, I got into programming because I wanted to make games as a kid.

Wolfenstein Title Screen It was around the time games started looking better and being more complicated than Wolfenstein 3-D that I started thinking I'd never be able to make a game. Sure, I could do Tetris or Minesweeper, but how in the world could I ever match the game play and graphics of a Quake or Diablo. Let's not even get started with Halo 3 and Call of Duty. More...


Like many programmers, I started doing this because of my interest in video games. I was 6 years old when I first touched a computer. It was an Apple IIe and I would play a game involving Donald Duck, his nephews, and a playground (I forget the name of the game). I was hooked, and took every available chance to play that I could.

Subsequently, I got a Nintendo and played all sorts of games. Super Mario Bros. was my favorite, of course, and it greatly inspired me. After a while, I was spending more time planning and drawing levels in my notebook for two-dimensional side-scrolling video games than I was playing them. It wasn't long before I envisioned my own game console. More...



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