IA on AI

Posts Tagged ‘smart objects’

Far Cry 2 – a little deeper look

Monday, March 24th, 2008

Back in January, I posted a snippet of a review regarding Ubisoft’s claim that the AI in Far Cry 2 was going to be seriously cutting edge. Well, apparently, Far Cry 2 was apparently a hit at the recent Play.com LIVE event at Wembley Stadium. According to this review at 411mania.com the AI was at impressive. Of course, many things can be made to be impressive in a tightly controlled demo, but I would like to at least give them the benefit of the doubt. Here’s some comments from the review:

Different factions and gangs are spread across the 50 square km environment, and it’s up to you who you befriend and who you turn into mortal enemies. Walking around the wasteland area, the guards patrolling the area didn’t seem very phased by the player’s presence, carrying on with their everyday duties, and it was at this point that the specifics of the AI became obvious. It’s evidently a very sophisticated system, as we were assured that the AI is totally non-scripted. Redding joked that the enemy AI is like “The Sims with guns,” and it was clear where he was coming from. In the small preview we were shown, guards stopped to chat amongst themselves, went off for smoke breaks, and generally busied themselves about the area. They didn’t look too happy when the player tried to steal one of their cars though! One guard in plain sight of the truck shouted out, and his comrades came running, forcing the player to hightail it out of there. Interestingly, the vehicles in the game have a detailed damage system, and you’ll have to physically get out and repair them if they take too many hits. In the demo we saw, the player tried to hijack an abandoned vehicle, which was plainly kaput, so the player had to open the bonnet and use a wrench to fix various parts. We couldn’t see LJ physically controlling this part, so I don’t know exactly how interactive this portion will be, but it’s a novel idea.

Just observing a few things here. It sounds like they are using a similar sort of A-life approach that may have been used in the game S.T.A.L.K.E.R. Although much maligned for some poor behavior, Crysis also had a lot of the very engaging “idle behaviors” that are mentioned here. They mentioned The Sims in there and I’m sure that’s a nod to the “smart objects” model that was pioneered to such great effect by that franchise.

The idea of multiple factions also lends a lot of potential depth to the character behaviors. It will be interesting to see how this is handled. One question that I would have is how the alliance system is implemented. That is, if you make an enemy of one person in a faction, do they now ALL hate you immediately? If you quietly kill one guy, do they all know or can you continue to deal with them all happy-smiley-like?

Going back to the matter of the AI, the intense gunfight around the straw huts revealed some interesting snippets about how enemies react to being shot. Location-specific damage is nothing new, but Far Cry 2 takes it one step further, as the goals and objectives of enemy AI may change according to where they’ve been hit. Shoot them in the foot, and sure, they’ll hop around in pain, but they’ll still be in good enough condition to keep plugging you with hot lead. But we were shown a scenario whereby an enemy had taken a bullet in the upper thigh/groin region and was obviously in a bad condition. His primary objective therefore changed to finding safety, and he could be seen limping off to hide in a building. Naturally, the player finished him off for good measure, but it’s refreshing to see enemies that don’t act like mere moving targets, rooted to the spot until either you die or they do. FPS fans often have to deal with this kind of AI logic, so it’s good to see enemies acting more like actual humans with real thought processes and the like.

It looks like they have hooked up not only the animations to the agent damage models, but also made a point to have the behaviors change as a result. I have seen a lot of the location damage animations lately, and occasionally we see behaviors change as a result of being under fire, but it is nice to see that people are trying to blend them both in. It is perfectly natural to expect an injured warrior to go off and try to lick his wounds to “fight another day”. How does this affect the overall gameplay, however? Will they give up if injured? Are they a factor still or do you still need to clean up all the riff-raff that is hiding around? That makes for an interesting dynamic if you now have to root out all the cowering wounded people.

Whether or not Far Cry 2 will be plagued by the same overachievment strain issues that it’s predecessor and cousin (Crysis) did remains to be seen. Prima fascia, they both looked pretty good at first only to be exposed later on. I, for one, would like to see these boundary-pushing experiments work. The AI world needs some successes in new stuff in order to open up people’s minds to even more experimentation in the future.

Good luck, Ubisoft.

F.E.A.R. sequel promises "visual density"

Wednesday, January 30th, 2008

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!

The AI of F.E.A.R

Thursday, November 15th, 2007

Once again, Alex Champandard at AIGameDev.com has posted another entry in his Reviews section. This review is on the very novel and groundbreaking AI of the FPS game, F.E.A.R.

As he typically does in his technical reviews, he specifically identifies 29 tricks to use in games. As with “The Sims“, a major component is that of “smart objects”. Also, how the AI agents in the game use those objects is very impressive. I’ve only played the downloadable demo of F.E.A.R. but I was impressed quickly by how the agents appeared to work together and with their environment. I would like to play the game further and then re-read this technical review.

As always, make a point of looking at the references section of his post. That is where the meat is.

The Sims AI

Thursday, November 15th, 2007

Alex Champandard over at AIGameDev.com has posted a technical review of the AI for “The Sims”. This is a fantastic article listing 21 tricks that can be used, at least in theory, in game AI development.
Please notice that Alex has put references at the end that point you to the source material – which is always good reading.