Group Behaviors

Seminal flocking papersCraig ReynoldsCraig Reynolds• Flocks, Herds, and Schools: A Distributed Behavioral Flocks, Herds, and Schools: A Distributed Behavioral

Model – SIGGRAPH 1987Model – SIGGRAPH 1987

• Steering Behaviors for Autonomous CharactersSteering Behaviors for Autonomous Characters

• MIT BS and MSMIT BS and MS

• Oscar awarded in 1998Oscar awarded in 1998

• EA, Dreamworks, Sony PlaystationEA, Dreamworks, Sony Playstation

Components of flockingThree factors influence accelerationThree factors influence acceleration• Move closer to centroid of Move closer to centroid of locallocal neighbors neighbors

• Avoid collisions with closest neighborsAvoid collisions with closest neighbors

• Maintain same velocity as neighborsMaintain same velocity as neighbors

Boid detailsSome physicsSome physics• f = ma f = ma

• Banking (when turning) is modeledBanking (when turning) is modeled

Some logicSome logic• Averaging acceleration urges leads to problemsAveraging acceleration urges leads to problems

– Do nothing when two vectors cancelDo nothing when two vectors cancel

• Prioritized allocation of movements to acceleration urgesPrioritized allocation of movements to acceleration urges

– Flock centering could be ignored to avoid an obstacleFlock centering could be ignored to avoid an obstacle

Components of flockingLocal perception of neighborsLocal perception of neighbors• Reduces computational complexityReduces computational complexity

– nn22 in number of boids otherwise in number of boids otherwise

• Improves realismImproves realism

– React to what you knowReact to what you know

– Mistakes will happenMistakes will happen

Local perception of neighborsXiaoyuan TuXiaoyuan Tu• Artificial Fishes: Autonomous Locomotion, Perception, and Artificial Fishes: Autonomous Locomotion, Perception, and

Behavior, SIGGRAPH 1994 with Demetri TerzopoulosBehavior, SIGGRAPH 1994 with Demetri Terzopoulos

• MoviesMovies

– Go Fish!Go Fish!

– The Undersea World of Jack CoustouThe Undersea World of Jack Coustou

• AwardsAwards

– Only woman ever to win the ACM dissertation awardOnly woman ever to win the ACM dissertation award

First Chinese (Tsinghua) and first from Canada as well!First Chinese (Tsinghua) and first from Canada as well!

Other sources for group dynamics

Helbing et al. – Escape PanicHelbing et al. – Trails

Robotics• Maja Mataric• Ron Arkin