CIS 588 AI Evaluation
for
World of Warcraft
Jonathan Schmoll
February 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 Priest
during his study of WOW’s creature behavior.
AI Behavior Study
• Terrain Navigation
This Primitive Owlbeast is pumped.
– Creatures will
generally move
straight at the player.
– Creatures will move
around obstacles
and over
mountainous terrain.
– Terrain that restricts
players also restricts
creatures.
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
This is where I run away.
• Social Behavior
– Some creatures will call out for aid if they are attacked.
– Less intelligent creatures (like beasts) will not help their
comrades.
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
Move along fellas, you don’t want none of this.
– Some creatures will
patrol a certain path.
– Some creatures will
wander around a
certain area.
– Some creatures will
just stand around like
goons.
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’?
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