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The Technology of F.E.A.R. 2: An Interview on Engine and AI Development
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The Technology of F.E.A.R. 2: An Interview on Engine and AI Development

December 19, 2008 Article Start Previous Page 5 of 6 Next

Something that was discussed is destructibility of the environments. In F.E.A.R. 2, how destructible are the environments, and how does that impact the AI's behavior?

MR: We fill the space with a lot of particles. We blow apart geometry, in terms of like, holes being blown out of walls, corners being taken out of pillars and whatnot, as well as different destruction levels for different prefabs in the world. For example, a car will have many different states that it will go through.

What you won't see in this game, and what you won't see in a lot of games, is a lot of physical pieces that fly around the environment and are very large. We certainly have bottles and cans and stuff that fly around, that don't really impact the AI.

So, you notice in a lot of games -- Gears 2 -- it's actually pretty sparse in the environment. That's because -- well, I imagine there are a lot of reasons, but one of the reasons is because the AI traditionally has a difficult time of dealing, intelligently, with a car that has just moved ten feet and is now in its nav mesh. And, again, these are things that have solutions that are coming online; both middleware is providing it as well as we internally are developing, working on systems so that the AI will intelligently handle such problems.

Returning to dynamic systems, as in Left 4 Dead, what about dynamic difficulty systems?

MR: In things like Left 4 Dead, and other titles, you will see the AI, if they see the player struggling with combat, they will perhaps spawn less of the AIs; perhaps spawn less of the difficult AIs, like you'll see less tanks, perhaps. I've actually seen, on Left 4 Dead servers, in playing, all of the sudden, when I'm playing in advanced, it kicks me down to normal because I'm not performing very well.

So those are the things that I think we'll see. Because the goal is to not punish the player; everyone agrees that no player wants to be punished. It's fun to get defeated every once in a while, and change your tactics up, but it's unfun to just be like water breaking against rocks the whole time.

Is it more challenging to implement?

MR: Not necessarily. You just really need to keep heuristics across gameplay sections, of how the player's doing. I think what you'll see is the difficulty levels, perhaps the three different difficult levels that you're used to seeing, will still be there, but they'll just be hidden behind the scenes.

As a designer, we'll still have the hit points for this character, and the accuracy this character, whether or not they play it on easy, medium, or hard. All that you'll see is, it'll be completely opaque to the player what difficulty level he's playing on. The game will dynamically switch between hard, easy, and medium, depending on what he's doing.

And, really... you never know what a game's difficulty levels are between developers. And, there are harder sections of the game than the beginning of the game, so what may be fine for you at the beginning, is not fine for you later in the game.

Or maybe there's a particularly poorly designed area in the game that is a lot more difficult than the rest of it; in which case, it would be nice to go, you know, "You've died three times in this area; we're going to kick you down to medium for let's say the next few minutes, and maybe we'll bump you back up to hard after a little bit." But don't tell the player about it. The point is that the player just wants to feel successful, and that he's moving through the content.

Do you find that, beyond things that are obvious -- we talked about hit points, accuracy -- there are untapped difficulty managing solutions?

MR: One thing is grenades. If a player is hunkered down in a particular location, we'll have the AI throw more grenades. That's one area where we could temper down; the AI could throw less grenades if you are in an easy setting, so you'll have more time to hunker down.

In a game like F.E.A.R. 2, when you activate slow-mo, there's a certain ratio of how fast the player moves versus how fast the AI moves. That's something that could be adjusted as well. Maybe if you're on easy, the player moves faster relative to how the AI moves, so you're more successful.

Another thing is penalties for death. If you have a checkpoint saved, and you have half your health, you progress forward. If you die, maybe if you're on an easier difficulty level, we will refill your health for you when you reload that checkpoint -- even though you only had half your health when the checkpoint happened.

I was wondering about AI squad behavior as well.

MR: We have a system where what we call "activity stats" basically looks at the environment, looks at where the player is, looks at where the AI is, and decides, "You know, it would be really beneficial for the enemy AI if enemy A would go to this cover node, and enemy B would go to this cover node, and we'll try to flank him." So it's like a way of coordinating the AI to fight against the player effectively.

Is that engrossing for the player? Is that how you look at it, when it comes to making these cooperative AI? It seems to be the general gist; it presents more challenge, and it makes the game feel more realistic, because the enemies are working together.

MR: Yeah, well, you definitely want that sensation. I mean, you definitely don't want a guy standing out in the middle of the open, and you want the feeling of "These guys are working against you." Particularly, we have callouts, which are just the things that the AI says, and it's great when you see a guy get damaged, and he says, you know, "I'm down!" and the other guy yells, "I've got your back!" and he will move in to attempt to cover him. It just feels like you're fighting against a more intelligent enemy.

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