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Artificial Intelligence in Games

(GATE-561)

Dr.Çağatay ÜNDEĞER

InstructorMiddle East Technical University, GameTechnologies

Bilkent University, Computer Engineering

&

General ManagerSimBT Inc.

e-mail : cagatay@undeger.com

Game Technologies Program – Middle East Technical University – Fall 2009

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Outline

• Objective and Scope of the Course• Course Outline• Course Requirements• Assessment Method• References

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Course Objective• Theoretical basics of artificial intelligence (AI)

• Practical application to behavior modeling in game development.

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Course Scope

• Part 1:– Introduction to game components, AI and role of AI in games

• Part 2:– Frequently used AI architectures, which can be used for

designing AI engines in games; • Part 3:

– Basic decision taking, search and path planning techniques towards detailed reasoning of a game entity.

• Part 4: – Group behavior which makes an individual entity take

decision considering a group of entity in coordination and cooperation.

• Part 5: – High and low level script programming issues, which is very

commonly used in games.

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Course Outline

• Introduction to Common Game Components– Environment– Scenario– Perception– Behaviour– Physics– Body Movement and Animation– Visual Effects– Sound Effects

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Course Outline

• Introduction To Artificial Intelligence (AI)– Description of AI – History of AI– AI Techniques

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Course Outline

• AI Architectures– Sense-Reason-Act Loop– Knowledge Representation

• Finite-State Machines• Hierarchical Finite-State-Machines• Production Systems• Semantic Networks

– Time Management

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Course Outline

• Decision Taking– Neural Networks– Decision Trees– Game Trees– Fuzzy Logic– Prolog

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Course Outline• Search and Path Planning

– Environment Modeling– Off-line Search Techniques

• Basic Search Techniques– Depth First Search– Breadth First Search– A* and Its Derivations

• Common Search Techniques – Hill-Climbing– Simulated Annealing– Random Trees– Probabilistic Roadmaps– Genetic Algorithms

• Hierarchical Planning Techniques• Path Smoothing Techniques

– On-line Search Techniques• RTA*• MTS• MTES

– Incremental Search Techniques• D*• D*Lite

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Course Outline

• Group Behaviors– Formations– Flocking– Multi-Agent Pursuit

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Course Outline

• Script Programming– Low Level Scripts– High Level Scripts

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Course Outline

• Paper/Assignment Presentations• Project Presentations

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Course Requirements

• Develop a small-scale AI project individually. • The project topics will be selected from a list of topics provided by the instructor (additional

topics can be proposed). • Implementation will be done in C++.

• Preferably with;– Visual Studio (V6.0 or .NET) or

– Borland C++ Builder (V6.0 or 2009).

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Assessment Method• A project will be developed including:

– Project Documents (Final Report, Source Code, Executables) 30%– Project Presentation and Demonstration 20%

• Assignments:– Implementation Assignments 25%– Paper Reading/Presentation Assignments

25%

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Project Topics• War Craft like strategy game with attack and defense behavior of two

opposing forces.– Number of students: preferably 2– Environment: A war craft like grid world environment with

obstacles.– User control: Locate defense forces and define their initial

defense mission by orders. Locate attack forces and define their initial attack mission by orders.

– Automated entities: Both defense and attack forces– Behavior: Defense forces defend a region (a small town etc.) and

try to prevent attack forces to enter their region autonomously. Attack forces try to kill defense forces and get protected area autonomously. User should not need to order the entities all the time. Entities should have enough intelligence to decide and navigate appropriately. For instance if attack is from north, most of them should go to north, and little should stay south (but not all).

– Visualisation: Looking environment from the top view.

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Project Topics• Hide and escape behavior of a group of tanks against a helicopter attack.

– Number of students: 1-2– Environment: A grid world environment with obstacles and mountains preventing line of sight.– User Controlled Entities: A simple helicopter with a formulized sensor range (depending on

the target velocity) and limited with field of view.– Automated entities: One or more tanks having a predefined scenario (navigation

corridor/path). Tanks have larger fixed sensor ranges and they know that helicopters have lower range, but does not know exact the range value. They just have an estimate.

– Behavior: A group of tanks moving through the navigation corridor/paths that are predefined in the scenario, but they can deviate from their path if they see a helicopter. Possible deviations are as follows:

• If no helicopter is seen, go through the path.• If a helicopter is seen that is far and/or not going directly towards you, estimate that it

hasn’t seen you and perform a hide behavior which may be:• Slow down or stop in order to prevent detection• Hide and stop behind a mountain area• Determine a new path to target location near to original path far from the helicopter area

and continue movement• If helicopter is near and going directly towards you• Split the group and escape randomly far from the helicopter until you feel safe.• If helicopter is invisible again, resume mission and go to target point.

– Visualisation: Looking terrain from the top view and just see the tanks detected by the sensors.

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Project Topics• Follow and help behavior:

– Number of students: preferably 2– Environment: polygonal (triangulated) navigation areas with

holes/gaps.– User Controlled Entities: A 3d main character controlled by the

user which can move freely in neighboring areas and jump between the areas having gaps in between.

– Automated entities: A 3d helper character. If 2 students are in the project, there will be some attack forces/aliens.

– Behavior: A 3d helper character following the main character in the environment. If 2 students are in the project, helper character will be defending the main character against the attacks with guns (sword and/or pistol, etc.). Some entities will be attacking entities against main and helper characters.

– Visualisation: 3d environment

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Project Topics• Dog fight:

– Number of students: 1– Environment: : A grid world environment with

mountains.– User Controlled Entities: One of the aircrafts may be

controlled by the user.– Automated entities: A group of opposing aircrafts– Behavior: Two groups of aircrafts are given a mission

path that are intersecting each other. When they come close two each other they will attack each other until one group is terminated and later on the winning group will continue on its predefined path. One of the aircrafts may be controlled by the user.

– Visualisation: may be a 3D view

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Project Topics• Traffic simulation:

– Number of students: 1-2– Environment: a connected graph with intersections and

roads having one or two way directions/lanes and one or multiple lanes within one direction. The number of lanes may be changing on a single road in different regions.

– User Controlled Entities: None or one car may be controlled by the user

– Automated entities: Traffic/cars in the environment.– Behavior: Traffic will be fully automated with cars

located around randomly.– Visualisation: Top view

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Project Topics• Two body (soldier) defense supported forward movement:

– Number of students: 1-2– Environment: A grid world environment with obstacles– User Controlled Entities: None– Automated entities: One of more two soldier groups attacking a

defended area with opposing forces.– Behavior: Defense forces will be still and firing the arrack forces.

If they are under fire, they fire less frequently and less correctly, but if they are not under fire, they fire more frequently and more correctly. Attack forces are in two body groups (in each group there are two soldiers). They are moving forward on their path (a corridor with a predefined with). But movement of each soldier is one by one. One will be hiding behind and obstacle and protecting the other; and the other will be moving forward (may be firing meanwhile). After the moving one hides behind an obstacle, the roles of soldiers are exchanged.

– Visualisation: Top view

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Project Topics• Firing with bombs and missiles against a moving

target:– Number of students: 1– Environment: An environment with some

obstacles– User Controlled Entities: Escaping entity is

controlled by the user.– Automated entities: Attacking entity – Behavior: Attacking entity will follow and try to

kill the other moving entity. Attacking entity should estimate the firing direction against an unknown estimated escape movement.

– Visualisation: May possibly be top view

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Project Topics• A backgammon like game (or something similar):

– Number of students: 1– User Controlled Entities: One side– Automated entities: The other side– Behavior: The other side will play

autonomously, but backgammon rules will be significantly differentiated (no ready source code should be used so the game should be something unknown).

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Project Topics• Intelligent sensing while moving:

– Number of students: 1– Environment: A grid or polygonal based city like environment with

obstacles preventing line of sight– User Controlled Entities: None or moving entity may be controlled by the

user– Automated entities: A moving entity and some entities in the city firing the

moving one with some random delays (they will be fixed or moving with a predefined scenario)

– Behavior: Moving entity will move on a predefined fixed navigation path and if see someone, it will shoot. Meanwhile moving it should maximize its perception in order not to be killed. Therefore it should:

• Kill anyone around• Look around to maximize vision• Look at sides while passing an obstacle corner to maximize vision• Look behind in order to detect someone pop up behind• Look at the direction that a sound (firing) is coming• Look at more dangerous ones with higher priority (but don’t forget

the others)• Track moving entities to keep seeing it

– Visualisation: Top view

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Project Topics– Bird behavior:

• Number of students: 1• Environment: A grid or polygonal base

environment with mountains and trees• User Controlled Entities: A man• Automated entities: Birds • Behavior: Birds are flying around randomly

or within a flock. Sometimes they stay on top of a tree. If the man is closer to them, they escape, avoid and go somewhere or fly to another tree.

• Visualisation: Any

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Project Topics• A generic AI engine:

– Number of students: 1-2

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References

• [1] “Artificial Intelligence and Soft Computing: Behavioral and Cognitive Modeling of the Human Brain”, Amit Konar, CRC Press, 2000

• [2] “Game Programming Gems”, Mark DeLoura, Charles River Media, 2000

• [3] “Artificial Intelligence: A Modern Approach”, Stuart Russel and Peter Norvig, Prentice Hall, 1995

• [4] “Machine Learning”, Tom M. Mitchell, 1997