Behavior

Autonomous Characters

Self-Directed characters "puppets that pull their own strings" -Ann Marion

Autonomous Characters

AcknowledgementMuch of this material is taken from the work of Craig Reynolds. He maintains a web pages including a rich source of material of steering behavior and the consumate source on flocking.

Also see: Steering Behaviors For Autonomous Characters

by Craig Reynolds

Three-Tier Hierarchy

Action selectiongoals and strategies “What to do”

Steeringguidance / motion control “How to do it”

Locomotionmovement generation “Getting it done”

Flocks in Film

1987: Stanley and Stella in: Breaking the Ice, (short) Director: Larry Malone, Producer: Symbolics, Inc.

1988: Behave, (short) Produced and directed by Rebecca Allen

1989: The Little Death, (short) Director: Matt Elson, Producer: Symbolics, Inc.

1992: Batman Returns, (feature) Director: Tim Burton, Producer: Warner Brothers

1993: Cliffhanger, (feature) Director: Renny Harlin, Producer: Carolco.

1994: The Lion King, (feature) Director: Allers / Minkoff, Producer: Disney.

Flocks in Film

1996: From Dusk Till Dawn, (feature) Director: Robert Rodriguez, Producer: Miramax

1996: The Hunchback of Notre Dame, (feature) Director: Trousdale / Wise, Producer: Disney.

1997: Hercules, (feature) Director: Clements / Musker, Producer: Disney.

1997: Spawn, (feature) Director: Dipp₫, Producer: Disney.

1997: Starship Troopers, (feature) Director: Verhoeven, Producer: Tristar Pictures.

1998: Mulan, (feature) Director: Bancroft/Cook, Producer: Disney.

Flocks in Film

1998: Antz, (feature) Director: Darnell/Guterman/Johnson, Producer: DreamWorks/PDI.

1998: A Bugs Life, (feature) Director: Lasseter/Stanton, Producer: Disney/Pixar.

1998: The Prince of Egypt, (feature) Director: Chapman/Hickner/Wells, Producer: DreamWorks.

1999: Star Wars: Episode I--The Phantom Menace, (feature) Director: Lucas, Producer: Lucasfilm.

2000: Lord of the Rings: the Fellowship of the Ring (feature) Director: Jackson, Producer: New Line Cinema.

Seeking and Fleeing

Seeking and Fleeing Applet (Reynolds)

Pursuing and Avoiding

Pursuing and Avoiding Applet (Reynolds)

Separation: Avoid Collisions

Alignment

Flocking Demos

Flocking Applet (Craig Reynolds) Fish Schooling (Steve Hughes) Beach House (Ishihama Yoshiaki )

For more demos see Reynolds “Boids in Java”

Do People Flock?

Social psychologist’s report the people tend to travel as singles or in groups of size 2 to 5.

Characteristics of Groups

Proximity Coupled Behavior Common Purpose Relationship Between

Members

Moving Formations

Pairs: Side by side Triples: Triangular shape

Stationary Formations

Moving pair approachesstationary triple

Stationary quintuple formed

Locomotion Model for Walking

Two Parameters Speed

Combination of step length and step rate

Orientation Head direction for forward walking

Accelerate Accelerate Accelerate Turn Left No Turn Turn Right

Coast Coast Coast Turn Left No Turn Turn Right

Decelerate Decelerate Decelerate Turn Left No Turn Turn Right

Action Space

Distributed Preference Voting

Delegation of voters: Constraint Proxies Proxies vote on each cell of the action space Votes are tallied Winning cell represents best compromise among

competing interests

Vote Tabulation

1.0

Pursuit Point

Tracking

Maintain Formation

Inertia

Centering

Maintain Target

Velocity

Avoid Peds

Winning Cell

Electioneer

1.0

1.0

2.0

2.0

4.0

5.0

Avoid Obstacles

A Group of Two Following a Path

ped 1

walkway axis

pursuit point

Winning vote = Accelerate/Turn Right

ped 2

-1.0 -1.0 +1.0-1.0 -1.0 +1.0-1.0 -1.0 +1.0

Pursuit Point Tracking

+1.0 +1.0 +1.0 -1.0 -1.0 -1.0 -1.0 -1.0 -1.0

Maintain Formation

+1.0 +1.0 +3.0 -3.0 -3.0 -1.0 -3.0 -3.0 -3.0

2.01.0

Election for ped 1

Avoiding an Obstacle -- Trajectory

Small look-ahead distance Large look-ahead distance

ped 1

ped 2

walkway axis walkway axis

ped 1

ped 2

Interaction Between Pairs -- 1

Interaction Between Pairs -- 2

Interaction Between Pairs -- 3