Game Development Reference
In-Depth Information
What the Character Wants
This can be stratified into base, long-term, short-term, and immediate de-
sires. Taking a
Star Wars
Stormtrooper as an example, we can assume that
his base desires—like those of almost any living being—will include staying
alive and unharmed, and seeing to his basic needs such as food, shelter,
etc. His long-term desires might include being a good Stormtrooper, fol-
lowing orders, and getting promoted. His short-term desire, building on
the previous, could be to capture or kill those darn Rebels currently skulk-
ing around the Death Star. And his immediate desire might be to shoot the
Rebel who's hiding behind cover just across the hangar bay.
Base and long-term desires remain constant for most characters
throughout a story (or game), but short-term and immediate goals can
shift rapidly based on changing circumstances. In a game, the situation
can evolve based on any number of predetermined or dynamic events, as
well as in response to unpredictable player actions. “Acting is reacting,” as
the old Hollywood saying goes, and this most definitely applies to in-game
AI-controlled characters.
How badly the character wants that thing should also be reflected in his
behavior. What is he willing to risk? With regard to video game characters,
this generally boils down to, is the character willing to pay the ultimate
price in pursuit of her desires? From an AI design perspective, the easy an-
swer is always “she's willing to die to get what he wants.” This makes pro-
gramming an enemy character a lot simpler, to be sure; she attacks until
either she or her target is defeated.
But a more nuanced and realistic AI model might incorporate the
concept of self-preservation and morale, with NPC characters who might
retreat or even surrender if things get too hairy. A more subtle version of
this concept might simply see the NPC becoming less aggressive when
things are going poorly—staying in cover, hunkering down, etc.—and more
aggressive when she perceives she has the upper hand.
What the Character Believes He Should Do
This does not necessarily align with the very best thing the character
could
do! But having a good understanding of who this character really is should
help an AI programmer know at all times what that character would think
is the best course of action given any circumstances that might emerge
during gameplay.
