Stealth article - first part

Beating a game using stealth often entails achieving, or coming closer to, your objective without being detected by and consequently confronting hostiles face-to-face. Basically hide and seek. Wanna play?

Stealth AI in action: The benefits of smoking


Steely Stan crouches behind the crate. Peeking around its side, he sees an evil dude standing twenty feet away near one of the pillars that keep the roof of this parking garage up. Evil dude is lighting a cigarette. Filthy habit. It's going to kill him someday. Stan draws back out of the line of sight, and considers his next move. The evil dude will definitely see him if he goes for the doorway now, but once there, it's smooth sailing through the dark corridor beyond. Oh well, better go prepared for the worst.
Reload time.
Just as Stan finishes reloading the silenced 9mm, he realizes his mistake. The sound of steps on concrete. They're closing in. Dammit. Never make noise this close to the evil dudes. They always hear. The steps sound few and far between. Hesitant, uneven. '
He hasn't seen me yet. I can still get out of this', Stan reassures himself. The evil dude comes to a halt on the other side of the crate, scratches some body part and mutters 'Oh well, must've been those damn rats again'. Stan can almost hear him shrugging.
As evil dude walks back, he takes another hit off the cancer stick and embarks on a coughing fit of epic proportions. His back is turned, he is bent over, red-faced and distracted.
'
This is as good a chance as I'm gonna get'. Stan holds his breath. And runs for it.
'
I think those cancer sticks actually saved your life, evil dude', Stan reminisces, as he slips undetected and grinning into the shadow beyond the dark doorway.

What defines the stealth genre and its gameplay?


Part of the answer may be found in the AI's behaviour and its relatively complex responsiveness to its environment.

The smoking evil dude has to rely on his limited senses to find the player. At no time does he automatically know where the player is. If he did, the game of hide and seek would be impossible. Evil dude has to have a point of view, and a limited field of perception. Whether he is equipped with ordinary sight and hearing, or x-ray vision is secondary. Evil dude's x-ray vision will come up against sheets of lead if he ever finds himself in a stealth game.

Some of those sheets of lead will probably be lining a box. A place for Steely Stan to hide from evil dude. That's a lucky break for Stan, and stealth game heroes in general, since they often have to move through an environment from A to B to get where they are going. Environments with places to hide from enemies.
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Event-driven finite state machines?!

look like good places to start off an explanation of the sort of game AI that appears to be employed in stealth games. 
Now. To explain this in easily understandable terms without getting overly technical.
I wonder if this should go in a separate AI concept. Finite state machines can be, and probably are, employed in the implementation of all kinds of Game AI. Not just stealthy evil dudes.
It wouldn't be explain pathfinding or chess AI, though. That's probably a different ballgame. Hmm. I'm fascinated by this stuff.
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Articles in the works

My plan so far, is to extend the stealth article. This will possibly extend to an AI article, something I'm surprised not to find in here. Here's my illustration of stealth gameplay. Let me know what you think.

Steely Stan crouches behind the crate. Peeking around its side, he sees an evil dude standing twenty feet away near one of the pillars that keep the roof of this parking garage up. Evil dude is lighting a cigarette. Filthy habit. It's going to kill him someday. Stan draws back out of the line of sight, and considers his next move.
The evil dude will definitely see him if he goes for the doorway now, but once there, it's smooth sailing through the dark corridor beyond. Oh well, better go prepared for the worst. Reload time. Just as Stan finishes reloading the silenced 9mm, he realizes his mistake. The sound of steps on concrete. They're closing in. Dammit. Never make noise this close to the evil dudes. They always hear. The steps sound few and far between. Hesitant, uneven. 'He hasn't seen me yet. I can still get out of this', Stan reassures himself.
The evil dude comes to a halt on the other side of the crate, scratches some body part and mutters 'Oh well, must've been those damn rats again'. Stan can almost hear him shrugging. As evil dude walks back, he takes another hit off the cancer stick and embarks on a coughing fit of epic proportions. His back is turned, he is bent over, red-faced and distracted. 'This is as good a chance as I'm gonna get'. Stan holds his breath and runs for it.
'I think those cancer sticks actually saved your life, evil dude', Stan reminisces, as he slips undetected and grinning into the shadow beyond the dark doorway.

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