Artificial Intellige..

895 Pages·2006·5.26 MB·English

by  Millington, Ian.

Ian Millington crossesthe boundary between academic and professional game AI with
hisbookArtificialIntelligenceforGames.Mostbookseitherlackacademicrigororare
rigorouswithalgorithmsthatwon’tworkundertheCPUconstraintsimposedbymodern
games.Thisbookwalksalinebetweenthetwoanddoesitwell.Itexplainsalgorithms
rigorously while also discussing appropriate implementation details such as scheduling
AIovertimeandusingtherightdatastructures.IwillbeusingthisbookformyGame
AIcourse.
—JessicaD.Bayliss,Ph.D.
RochesterInstituteofTechnology
ThisisthefirstseriousattempttocreateacomprehensivereferenceforallgameAIprac-
tices, terminology, and know-how. Works like this are badly needed by the maturing
videogamesindustry.Systematicyetaccessible,itisamust-haveforanystudentorpro-
fessional.
—MarcinChady,Ph.D.
RadicalEntertainment
ThisbookpromisestobetheclosestI’veseentowhatisneededinthefield.Iwouldhighly
recommenditforpeopleintheindustry.
—JohnLaird
UniversityofMichigan
IanMillington’sbookisacomprehensivereferencetothemostwidelyusedtechniquesin
gameAItoday.AnygamedeveloperworkingonAIwilllearnsomethingfromthisbook,
andgameproducersshouldmakesuretheirAIprogrammershaveacopy.
—Dr.IanLaneDavis
MadDocSoftware
TheMorganKaufmannSeriesinInteractive3DTechnology
SeriesEditor:DavidH.Eberly,GeometricTools,Inc.
Thegameindustryisapowerfulanddrivingforceintheevolutionofcomputertech-
nology. As the capabilities of personal computers, peripheral hardware, and game
consoles have grown, so has the demand for quality information about the algo-
rithms,tools,anddescriptionsneededtotakeadvantageofthisnewtechnology.To
satisfythisdemandandestablishanewlevelofprofessionalreferenceforthegamede-
veloper,wecreatedtheMorganKaufmannSeriesinInteractive3DTechnology.Books
intheseriesarewrittenfordevelopersbyleadingindustryprofessionalsandacademic
researchers,andcoverthestateoftheartinreal-time3D.Theseriesemphasizesprac-
tical,workingsolutionsandsolidsoftware-engineeringprinciples.Thegoalisforthe
developertobeabletoimplementrealsystemsfromthefundamentalideas,whether
itbeforgamesorforotherapplications.
ArtificialIntelligenceforGames PhysicallyBasedRendering:FromTheory
IanMillington toImplementation
MattPharrandGregHumphreys
BetterGameCharactersbyDesign:
APsychologicalApproach
EssentialMathematicsforGamesand
KatherineIsbister
InteractiveApplications:AProgrammer’s
VisualizingQuaternions Guide
AndrewJ.Hanson JamesM.VanVerthandLarsM.Bishop
3DGameEngineArchitecture:
GamePhysics
EngineeringReal-TimeApplicationswith
DavidH.Eberly
WildMagic
DavidH.Eberly
CollisionDetectioninInteractive3D
Real-TimeCollisionDetection Environments
ChristerEricson GinovandenBergen
Forthcoming
X3D:Extensible3DGraphicsforWeb 3DGameEngineDesign:APractical
Authors ApproachtoReal-TimeComputer
LeonardDalyandDonBrutzman Graphics,2ndEdition
DavidH.Eberly
GamePhysicsEngineDevelopment
IanMillington Real-TimeCameras
MarkHaigh-Hutchinson
ARTIFICIAL
INTELLIGENCE
FOR GAMES
IANMILLINGTON
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ISBN13:978-0-12-497782-2
ISBN10:0-12-497782-0
ISBN13:978-0-12-373661-1(CD-ROM)
ISBN10:0-12-373661-7(CD-ROM)
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To Conor
A A
BOUT THE UTHOR
IanMillingtonisapartnerofIcosagonLtd.(www.icosagon.com),aconsultingcom-
panydevelopingnext-generationAItechnologiesforentertainment,modeling,and
simulation. Previously he founded Mindlathe Ltd, the largest specialist AI middle-
warecompanyincomputergames,workingwithonahugerangeofgamegenresand
technologies.HehasalongbackgroundinAI,includingPhDresearchincomplexity
theoryandnaturalcomputing.Hehaspublishedacademicandprofessionalpapers
andarticlesontopicsrangingfrompaleontologytohypertext.
vi
C
ONTENTS
ABOUT THE AUTHOR
vi
LIST OF FIGURES
xxi
ACKNOWLEDGMENTS
xxix
PREFACE
xxxi
ABOUT THE CD-ROM
xxxiii
P I
ART
AI AND GAMES 1
CHAPTER
1
INTRODUCTION
3
1.1 WHAT IS AI? 4
1.1.1 AcademicAI 5
1.1.2 GameAI 7
1.2 MY MODEL OF GAME AI 9
1.2.1 Movement 10
1.2.2 DecisionMaking 10
1.2.3 Strategy 11
1.2.4 Infrastructure 11
1.2.5 Agent-BasedAI 12
1.2.6 IntheBook 12
1.3 ALGORITHMS, DATA STRUCTURES, AND
REPRESENTATIONS 13
1.3.1 Algorithms 13
1.3.2 Representations 16
vii
viii Contents
1.4 ON THE CD 17
1.4.1 Programs 17
1.4.2 Libraries 18
1.5 LAYOUT OF THE BOOK 19
CHAPTER
2
GAME AI
21
2.1 THE COMPLEXITY FALLACY 21
2.1.1 WhenSimpleThingsLookGood 21
2.1.2 WhenComplexThingsLookBad 22
2.1.3 ThePerceptionWindow 23
2.1.4 ChangesofBehavior 23
2.2 THE KIND OF AI IN GAMES 24
2.2.1 Hacks 24
2.2.2 Heuristics 25
2.2.3 Algorithms 27
2.3 SPEED AND MEMORY 27
2.3.1 ProcessorIssues 28
2.3.2 MemoryConcerns 31
2.3.3 PCConstraints 32
2.3.4 ConsoleConstraints 32
2.4 THE AI ENGINE 35
2.4.1 StructureofanAIEngine 35
2.4.2 ToolchainConcerns 37
2.4.3 PuttingItAllTogether 38
P II
ART
TECHNIQUES 39
CHAPTER
3
MOVEMENT
41
3.1 THE BASICS OF MOVEMENT ALGORITHMS 42
3.1.1 Two-DimensionalMovement 43
3.1.2 Statics 44
3.1.3 Kinematics 47
3.2 KINEMATIC MOVEMENT ALGORITHMS 51
3.2.1 Seek 52
3.2.2 Wandering 55
ix
3.2.3 OntheCD 57
3.3 STEERING BEHAVIORS 57
3.3.1 SteeringBasics 58
3.3.2 VariableMatching 58
3.3.3 SeekandFlee 59
3.3.4 Arrive 62
3.3.5 Align 66
3.3.6 VelocityMatching 69
3.3.7 DelegatedBehaviors 70
3.3.8 PursueandEvade 71
3.3.9 Face 74
3.3.10 LookingWhereYou’reGoing 75
3.3.11 Wander 76
3.3.12 PathFollowing 79
3.3.13 Separation 85
3.3.14 CollisionAvoidance 88
3.3.15 ObstacleandWallAvoidance 94
3.3.16 Summary 99
3.4 COMBINING STEERING BEHAVIORS 100
3.4.1 BlendingandArbitration 100
3.4.2 WeightedBlending 101
3.4.3 Priorities 107
3.4.4 CooperativeArbitration 111
3.4.5 SteeringPipeline 113
3.5 PREDICTING PHYSICS 126
3.5.1 AimingandShooting 126
3.5.2 ProjectileTrajectory 127
3.5.3 TheFiringSolution 129
3.5.4 ProjectileswithDrag 132
3.5.5 IterativeTargeting 134
3.6 JUMPING 140
3.6.1 JumpPoints 141
3.6.2 LandingPads 145
3.6.3 HoleFillers 149
3.7 COORDINATED MOVEMENT 151
3.7.1 FixedFormations 151
3.7.2 ScalableFormations 153
3.7.3 EmergentFormations 153
3.7.4 Two-LevelFormationSteering 155
3.7.5 Implementation 158
3.7.6 ExtendingtoMorethanTwoLevels 165
3.7.7 SlotRolesandBetterAssignment 167