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In game AI - discussion

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August 20, 2003 6:52:52 PM

I was playing the XIII demo (nice demo btw. Thanks marvelii) and noticed the guards in the second map behaved in different ways. Some just come straight at you. One crouched down and just waited, essentially camping. Another played hide and seek behind some boxes. Yet another ran away and hid in another room.

Whichever plan the guards choose, be it charge, hide, duck, camp, whatever, they seem to stick with it.

The guards are still not what I would consider smart but at least they weren't running around in circles.

I was just wondering what games have above average AI and why do you think the AI is better than average?

<b>56K, slow and steady does not win the race on internet!</b>

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August 20, 2003 10:23:45 PM

Why the AI is better than in most games? This is easy, the developpers spent more time on it. For each type of stance(charge, hide ...) you have to set different parameters for the bot's movements. Also you have to figure out a way to choose which type of stance a guard takes depending on the circumstance.

This takes time, and time = money. Also these days the accent is put on great graphics more than good gameplay.

In ancient times they had no statistics so they had to fall back on lies
August 20, 2003 10:47:01 PM

Well, graphics and multiplayer get the emphasis I'd say.

Although AI plays an important part in single player. Story and a good balance of action and difficulty are more important.

On the other hand, bad AI can really ruin a game.

Do you have any examples of games with good AI?

<b>56K, slow and steady does not win the race on internet!</b>
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August 20, 2003 10:48:01 PM

I've been teaching myself AI from a programming perspective and I think it's because they don't want to slow down computers too much. First of all, if game developers were to run a separate neural net for every single bot in the game, games today would run really slowly. Most bots in games don't respond "intelligently" based on your behaviour. Instead, they behave the same way every single time you play the game. Another reason is time, the time it takes to train a neural net to behave intelligently might be too long given a tight schedule.

Intelligence is not merely the wealth of knowledge but the sum of perception, wisdom, and knowledge.
August 21, 2003 12:08:07 AM

I guess AI is a bad term to use. I'm just referring to bot and game behavior that seems reasonable.

Examples of bad behavior include bots that ignore you even though alarms have been sounded. How about bots that don't hear you when you shoot guns? Worse, bots that don't know you are shooting them! Other bad behavior include guards that cower in closet on the 7th floor when you have silently dispatched a guard on the first floor. (How do they know?) Being seen in impossible places and bots with uncanny marksmanship are particularly annoying (MOHAA comes to mind).

<b>56K, slow and steady does not win the race on internet!</b>
August 21, 2003 5:03:29 AM

half life had some of the best ai for its time. those ninja chicks that had the cloak were like playing real sneaky people. an example of bad ai is grandtheft auto. the characters that are following you just try to move in a straight line toward you. if they get stuck in a pool or somthing they cant get out, they have no concept of jumping. the bank robbery mission in vice city pissed me off cause the stupid people following you would get stuck on corners and behind desks. i mean hell, the hosties in counter strike at least follow the path you took, they can get stuck but they are a million times better than gta.

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August 21, 2003 2:53:10 PM

I should replay Half Life (but I didn't enjoy it as much as most people).

The last single player FPS I enjoyed was Star Trek Voyager Elite Force. (It was the only Star Trek game I enjoyed). I don't recall the AI being anything special but nor did it stand out as being really bad. Elite Force was too short, though.

System Shock 2 was a great game but really old. I don't really remember the AI (but again it didn't stick out as being bad). The story was so good and the suspense factor was the best part of the game.

Speaking of bad AI, this is not about an FPS. I used to enjoy the Close Combat series of RTS games. One day I was playing A Bridge too Far and had a squad trying to sneak down the side of the road. The squad was behind some hedgerows. I plotted them to move behind the cover but no matter how I had them move fast, normal, or sneak they always moved out in front of the hedgerow. This would put them in the open road right in front of enemy armor. Now that's bad AI!

<b>56K, slow and steady does not win the race on internet!</b>
August 21, 2003 3:40:08 PM

You're right, the accent put on multiplayer these days results in the fact that the game developper spend more time on that part of the game than on AI.

Also, I beleive that more elaborate AI would not slow down modern machines. You do not have to keep track of all the bots in the game, just keep track of a couple bots ahead of the player. In this way the quantity of computation required is not too much. Considering that modern computers have twice as much power than those 2 or 3 years ago, I did not see such an improvement in the AI.

I haven't find I game with memorable AI, altough when I first play RTCW, I found that the bot did a couple of nice tricks but nothing incredible.

In ancient times they had no statistics so they had to fall back on lies
August 22, 2003 5:45:29 PM

Has nobody played No One Lives Forever 2?

It's got quite probably the best AI in any game released to date. The bots have jobs to do, for instance the guards have guard duty, scientists work on machines, clerks use desks and filing cabinets... But they also have desires. As a guard's thirst goes up, he gets more and more likely to go to the can machine. If he smokes, he'll want to go for a cigarette every so often. Once he gets back, he'll find the nearest guard point or patrol route that isn't being manned and guard it.

Different NPCs have different attention spans. Some guards are just plain lazy, and if they see you they'll only put in a half-hearted chase; the elite ones will pursue you for ages. They respond to changes in the environment; once I saw a guard walking around in the snow, and he saw some footprints and started following them. I laughed my arse off as he followed his OWN footsteps around a building, and eventually got bored and went for a smoke :p 

The combat AI is great too. I was fighting three ninjas next to a building; I killed one, and there was one left. I just had time to go "huh?" before the other one stabbed me in the back; she'd snuck AROUND the building, while her friends distracted me. Now THAT'S intelligence!
August 23, 2003 3:33:52 PM

Nope, never played No One Lives Forever 2, but it sounds like I should. AI seems impressive.

In ancient times they had no statistics so they had to fall back on lies
August 24, 2003 12:20:51 AM

That's great to hear. Is the NOLF2 a good game?

Does the demo exhibit the same level of AI?

I'll take a look.



<b>56K, slow and steady does not win the race on internet!</b>
August 24, 2003 2:26:15 AM

NOLF 2 is a great game. Its AI is top notch. Enemies dont just run around shooting they actually look for you for a long period of time. When they spot you its like a whole swarm of enemies come after you. The game can get very funny at times which is a plus. I never finished the game...maybe I will now since im waiting for a good fps to come out.

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August 24, 2003 5:12:19 AM

Actually, I wasn't too impressed by the enemy AI in NOLF 2. If the enemy has evidence that you are around, you can be hiding in a corner, perfectly still, and the enemies will immediatly turn to face you and start shooting once they enter the room you are in, without having to look around at all. Unless the cornor you are crouching in is a considered a hiding place within the level. In fact, the whole concept of having designated "hiding places" in levels instead of doing up AI routines to determine if an enemy can tell where you are hiding always annoyed me.

Still, its a good game, though I liked NOLF 1 way better.
August 24, 2003 12:04:27 PM

I agree, the hiding places thing was a bit lame. I'm looking forward to Thief 3, which should have true darkness detection.

NOLF 1 was a better overall game, but in terms of enemy AI, NOLF 1 took the title way back when, and NOLF 2 took over when it came out. Haven't seen anything else that comes close since.
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