Ted Vessenes wrote a nifty little post on his blog where he compared designing and programming AI to being a parent. Here's the opening paragraph:

"Writing artificial intelligence is a lot like being a parent. It requires an unbelievable amount of work. There are utterly frustrating times where your children (or bots) do completely stupid things and you just can't figure out what they were thinking. And there are other times they act brilliantly, and all the effort feels satisfying and well spent."

I have to agree with a lot of the points he makes in his post. I would like to take the analogy one step farther.

I've occasionally made the point about both parenting and AI that your job is to not define what your progeny should do but convey an understanding of why. If, as a parent, you tell your child not to run in the street, they will hopefully carry that lesson into the future. However, they may not apply that same edict to driveways, parking lots or any other places where they could get plowed over by a car. This is analogous to the scripted AI methodology. However, if you explain the why of the situation - i.e. "be careful anywhere that cars are moving because the driver may not see you in time to stop and you could get badly hurt" - then the simple rule can be applied to any situation where there are cars (or even car-like objects). This, of course, maps over to rule-based systems or even planning systems.

However, going back to Ted's point, it is an interesting similarity to put all those rules into place and hope that your little bots realize the appropriate situations in which to use them. I actually wrote a column about this scary process on my weekly column over at AIGameDev.

Anyway, if you are an AI developer, I hope that you are blessed with many children who all grow up to be accomplished in their chosen lives (or deaths).

Labels: agent based AI, AIGameDev, bots, planning, scripting

I noticed this GamePro blurb about the upcoming sequel to F.E.A.R. Here's an excerpt...

"The most obvious difference that will hit the player right away is in the visual density of the world," said Mulkey. "F.E.A.R. looked really great, but where F.E.A.R. would have a dozen props in a room to convey the space, Project Origin will have five times that much detail.

"Of course, this will only serve to further ratchet up that 'chaos of combat' to all new levels with more breakables, more debris, more stuff to fly through the air in destructive slow motion beauty."

OK... I can dig that. One thing I noticed as I played through F.E.A.R. is that things were kinda sparse. (I really got tired of seeing the same potted cactus, too.)

The part that I am curious about, however is this:

... Mulkey says improved enemy behavior is at the top of the list.

"We are teaching the enemies more about the environment and new ways to leverage it, adding new enemy types with new combat tactics, ramping up the tactical impact of our weapons, introducing more open environments, and giving the player the ability to create cover in the environment the way the enemies do," he says.

Now that is the cool part. When the enemies in the original moved the couches, tables, bookshelves, etc. it was cool... but rather infrequent. I was always expecting them to do more with it. If they are both adding objects to the environment and then "teaching" the agents to actually use those objects, we may see a level of environment interactivity that we've never experienced before.

The cool thing about their planning AI structure is that there isn't a completely rediculous ramp-up in the complexity of the design. All one needs do is tag an object that it can be used in a certain way and it gets included into the mix. On the other hand, having more objects to use and hide behind does increase the potential decision space quite a bit. It's like how the decision tree in chess is far greater than that of Tic-tac-toe because there are so many more options. The good news is that the emergent behavior level will go through the roof. The bad news is that it will hit your processor pretty hard. Expect the game to be a beast to run on a PC.

I certainly am looking forward to mucking about with this game!

Labels: agent based AI, emergence, F.E.A.R., FPS, Monolith, planning, smart objects, using cover

I hate glomming on to a blog chain, but I'm going to link to AIGameDev's article on an article (which may very well be about an article.) The title is Watching Level Designers Use Scripts to Disable Your Autonomous AI: Priceless - which just about covers it. Alex does a nice job of not just reporting on it, but explaining the mindset and even the things to watch out for.

Regular readers of my other blog, Post-Play'em will know that I talked about the idea of scripts over-riding AI behaviors in Call of Duty 2 in a post entitled Call of Duty 2: Omniscience and Invulnerability. Specifically, this was in reference to one of the behaviors mentioned in the other article where an AI agent takes on a temporary god-like quality of invulnerability until such time as he finishes a scripted event - at which time he is no longer important to the level designer's wishes and is cast back into the pot of cannon fodder so that I can mow him down properly.

Getting back to the initial topic, my thought is that part of the issue between artists/level designers and programmers may very well be that the level designers don't have a trust in the capabilities of autonomous AI agents... or even and understanding of what could be done with them.

For example, with the use of goal-based agents such as those found in F.E.A.R. (related post), rather than a designer saying "I want the bot to do A then B, then C on his way to doing the final action of D." he could simply tell the goal-based agent that "D is a damn good goal to accomplish." If constructed properly, the agent would then realize that a perfectly viable way of accomplishing D would be via A-B-C-D. The difference between these two methods is important. If C is no longer a viable (or intelligent looking) option, then the scripted bot either gets stuck or looks very dumb in still trying to accomplish D through that pre-defined path. The very nature of planning agents, however, would allow the agent to try to find other ways of satisfying D. If one exists, he will find it. If not, perhaps another goal will suffice.

The problem is, while AI programmers understand this concept (especially if you are the one who wrote the planner for that game), level designers and particularly artists, may not have an intuitive grasp on this. They are cut more from the cloth of writers - "and then this happened, and then this, and then it was really cool when I wrote this next thing because I wanted the agent to look smart, and then this..." That is being a writer - and is why many games continue to be largely linear in nature. You are being pulled through an experience on a string of scripted events. (See related post on Doom 3's scripting vs. AI)

So, can the problem of designers trumping AI programmers be solved? It will always be there to some extent. But education and communication will certainly help the matter.

Labels: AIGameDev, Alex Champandard, emergence, planning, Post-Play'em, predictable, scripting

Time for a taste of the Lyon, France Game Developers Conference!

Alex Champandard at AIGameDev.com posted part 1 of a presentation he gave on the use of behavior trees in game AI.

Seriously good stuff!

(note: there may be a problem viewing the videos with IE - they work fine in Firefox.)

Labels: AIGameDev, Alex Champandard, behavior trees, planning, presentation, video

Alex at AIGameDev has a great essay up entitled "Memento, Temporal Coherence and Debugging Planners". In it, he talks about how planning algorithms have the problem of having their assumptions about the world fall quickly out of scope as the world changes. One solution is to continually replan from scratch - which can become quite expensive to do for numerous agents.

He offers a couple of solutions - and the comments on the post have turned into a rather interesting discussion on the caveats and possibilities. Check it out!

Labels: AIGameDev, Alex Champandard, planning