Video game ai 9 24 2008 prof janice t searleman jets@clarkson edu jetsza
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Video Game AI 9-24-2008 Prof. Janice T. Searleman jets@clarkson.edu , jetsza CS451/CS551/EE565 ARTIFICIAL INTELLIGENCE Outline Video Game AI Agents Knowledge-Based Agents Wumpus world Logic in general - models and entailment Propositional (Boolean) logic HW#4 due: Friday 10/03

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CS451/CS551/EE565 ARTIFICIAL INTELLIGENCE

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Video Game AI

9-24-2008

Prof. Janice T. Searleman

jets@clarkson.edu, jetsza

CS451/CS551/EE565ARTIFICIAL INTELLIGENCE


Outline

  • Video Game AI Agents

  • Knowledge-Based Agents

    • Wumpus world

    • Logic in general - models and entailment

    • Propositional (Boolean) logic

      HW#4 due: Friday 10/03

      Exam#1 – tentatively October 7th, 7:00 pm

      Reading: AIMA Chapter 7

      plus the handout on Video Game AI


Video Game AI

  • Video game AI agent

    • both challenging & also enjoyable to play

    • have very limited resources

  • Navigation &

    Path-finding


Game AI & typical usage


Simple map for a Non-Player Character (NPC)


Simple graph for a Non-Player Character (NPC)


Offensive & Defensive Strategies


Partitioning a map into zones


NPC Behavior


Finite State Machine (FSM)

  • FSM for a sentry NPC

  • If the Player is in sight, the NPC attacks; otherwise it marches between location X and location Y


Layered Behavior Architecture

Rodney Brooks’ Subsumption Architecture

Brooks, R.A., "How to build complete creatures rather than isolated cognitive simulators," in K. VanLehn (ed.), Architectures for Intelligence, pp. 225-239, Lawrence Erlbaum Assosiates, Hillsdale, NJ, 1991.


Goals and Plans


Team AI: cooperative agents


Rule-Based Systems

  • Called a Production System

  • Useful for real-time strategy AI

  • Working memory contains percepts on the current situation

  • Relevant rules are “triggered”

  • One rule is selected to “fire” (conflict resolution


Production Rules

  • R1: if the human opponent creates an expansion

    (nexus/hatchery/command_center) AND

    you possess sufficient military units

    then

    Attack the expansion

  • R2: if the map is a relatively small land map AND

    the location of the opponent is known AND

    your race is zerg

    then

    execute the four pool strategy

    Four pool strategy: make a spawning pool with your fourth drone and make another drone, and when the spawning pool is completed create as many zerglings as your crystals/larvae will allow, and attack your opponent with the zerglings.


Reasoning Agents


Knowledge bases

  • Knowledge base = set of sentences in a formal language

  • Declarative approach to building an agent (or other system): Tell it what it needs to know

  • Then it can Ask itself what to do - answers should follow from the KB

  • Agents can be viewed at the knowledge level

    i.e., what they know, regardless of how implemented

  • Or at the implementation level i.e., data structures in KB and algorithms that manipulate them


A simple knowledge-based agent

  • The agent must be able to:

    • Represent states, actions, etc.

    • Incorporate new percepts

    • Update internal representations of the world

    • Deduce hidden properties of the world

    • Deduce appropriate actions


Performance measure

gold +1000, death -1000

-1 per step, -10 for using the arrow

Environment

Squares adjacent to wumpus are smelly

Squares adjacent to pit are breezy

Glitter iff gold is in the same square

Shooting kills wumpus if you are facing it

Shooting uses up the only arrow

Grabbing picks up gold if in same square

Releasing drops the gold in same square

Sensors: Stench, Breeze, Glitter, Bump, Scream

Actuators: Left turn, Right turn, Forward, Grab, Release, Shoot

Wumpus World PEAS description


Wumpus world characterization

  • Fully Observable No – only local perception

  • DeterministicYes – outcomes exactly specified

  • Episodic No – sequential at the level of actions

  • Static Yes – Wumpus and Pits do not move

  • Discrete Yes

  • Single-agent? Yes – Wumpus is essentially a natural feature


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


Exploring a wumpus world


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