CIS 588 AI Evaluationfor

World of Warcraft

Jonathan SchmollFebruary 14, 2005

About World of Warcraft

• Henceforth referred to as “WOW”– Created by Blizzard Entertainment– Release November 23, 2004– Currently the #1 game in its genre

• WOW is a MMORPG:– Massively Multiplayer Online Role Playing

Game

Artificial Intelligence in WOW

• Used to control (mainly) enemy NPCs

• Used in almost all enemy functions– Movement– Attacking– Social Behavior

• Some scripting used for special encounters

WOW’s AI Implementation~ or: Blizzard Doesn’t Care That I’m a Grad Student

Doing a Presentation On AI

• Uses a strongly rules-based approach– Apparently based on expert systems– Special scripting does not break AI rules– Possibly uses Lua scripting language

• Blizzard did not want to divulge their secrets– Info based on obtuse contact with Blizzard,

Internet research, and a lot of forum trolling.

AI Behavior Study

The following slides detail the adventures of

Johnny the Human Priestduring his study of WOW’s creature

behavior.

AI Behavior Study

• Terrain Navigation– Creatures will

generally move straight at the player.

– Creatures will move around obstacles and over mountainous terrain.

– Terrain that restricts players also restricts creatures.

This Primitive Owlbeast is pumped.

AI Behavior Study

• Terrain Navigation (cont.)

– Some creatures will not follow you into water.

Now who’s tough, Mr. Can’t Swim.

AI Behavior Study

• Creature Aggression– If a creature

knows it can kill you, it will go out of its way to attack you.

– Simulates how much a creature “fears” a player.Obviously this dragon isn’t too afraid of me.

AI Behavior Study

• Creature Aggression (cont.)– Weaker creatures will

not attack until the player is very close.

– Some creatures will regard the player as neutral.

– Some creatures will attack other creatures.

This is why you don’t leave your chickens out.

AI Behavior Study

• Social Behavior– Some creatures will call out for aid if they are

attacked.– Less intelligent creatures (like beasts) will not help

their comrades.

This is where I run away.

AI Behavior Study

• Fleeing– More intelligent

“humanoid” creatures will attempt to run when they are about to die.

– Beasts will fight to the death.

This is bear is going down. Hard.

AI Behavior Study

• Movement– Some creatures

will patrol a certain path.

– Some creatures will wander around a certain area.

– Some creatures will just stand around like goons.

Move along fellas, you don’t want none of this.

AI Behavior Study

• Attack Range– Ranged attackers

will attempt to keep their distance.

– Melee attackers will get right up in your face.

This troll didn’t appreciate my Jolly Green Giant jokes.

AI Behavior Study

• Special Abilities– Some creatures

have special abilities and will use them during battle (for example, healers will heal their comrades and themselves.)

Whitemane revives her buddy while my party members take a nap.

AI Strengths & Weaknesses

• Strengths– Relatively Bug-

free– Doesn’t feel

“cheap”– Works well for the

MMORPG genre– Is difficult to

exploit– Is predictable

• Weaknesses– Doesn’t “learn”– Has limited

options– Is predictable

AI’s Effect On Gameplay

• Creatures first appear very smart– This lends itself very well to the “small

player in a big world filled with monsters” adventure aesthetic.

• The AI is fairly transparent– This sounds like a bad thing, but it isn’t.

As your character “grows”, so does your understanding of creature behavior.

AI’s Effect On Gameplay (cont.)

• The gameplay changes as you level up.– Since high level players have seen most of the

game world, the adventure aesthetic becomes less important.

– Game play becomes more strategic.– Creatures are extremely powerful at high levels.

Unpredictable behavior would be frustrating when there is a penalty for dying and there is no “reload” option WOW’s persistent game world.

AI’s Effect On Gameplay (cont.)

• Scripting adds flavor– Scripted creature behavior inside special

dungeons adds a controlled unpredictability to the game. Players are forced to quickly come up with solutions to these “puzzles”.

– Scripted events still work within the creature’s AI rules (for example, a healer will not suddenly begin performing warrior abilities.)

Questions / Comments ?

Who doesn’t like a little gnome-on-human dancin’?