Michael Zyda [e-mail] Week 3 Initial Steps Character

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Character Following

• Michael Zyda
• Zyda_at_isi.edu

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Week 3 Initial Steps Character Following,
Flocking, Formations Coordinated Movement

• Project 3 Develop a simple AI client that
  selects a character in the game and begins to
  follow and taunt that character. Add in a flock
  of characters that follow and taunt the live
  player.
• Reading http//www.aiwisdom.com/bytopic_flocking.
  html

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What is annoyance?
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Flocking

• Craig Reynolds
• Go right here for information
• http//www.red3d.com/research.html
• http//www.red3d.com/research.html

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Reynolds Site

• Boids (Flocks, Herds, and Schools a Distributed
  Behavioral Model) background and update on the
  1987 model of group motion in flocks, herds,
  schools and related phenomena. Includes a Java
  demonstration.
• Steering Behaviors For Autonomous Characters
  techniques for obtaining goal- directed motion in
  self-directed animated characters. Includes Java
  demonstrations and a technical paper.
• Navigational Overview a carefully annotated
  survey of techniques for navigation, pathfinding
  and collision avoidance for robots and autonomous
  characters.
• Individual-Based Models a collection of models
  based on simulating the behavior of individuals
  (plants and animals in ecosystems, vehicles in
  traffic, characters in animation) and the global
  consequences of their local interactions.
• Improvisational Characters links to resources on
  autonomous characters that can improvise and
  react to their environment. Touches on
  characters, creativity, participatory ecosystems,
  game AI, robots, agents and multi-agent systems.
• Evolutionary Computation and its application to
  art and design. Using genetic algorithms and
  related techniques to create motion, shape,
  images and music.
• Stylized Depiction a survey of
  non-photorealistic techniques in computer
  graphics and animation. Includes painterly, toon
  and sketchy rendering, painterly image
  processing, and detailed simulation of
  traditional artistic media.

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Reynolds Boids

• In 1986 I made a computer model of coordinated
  animal motion such as bird flocks and fish
  schools.
• It was based on three dimensional computational
  geometry of the sort normally used in computer
  animation or computer aided design. I called the
  generic simulated flocking creatures boids.
• The basic flocking model consists of three simple
  steering behaviors which describe how an
  individual boid maneuvers based on the positions
  and velocities its nearby flockmates

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Steering Behaviors

• Separation steer to avoid crowding local
  flockmates
• Alignment steer towards the average heading of
  local flockmates
• Cohesion steer to move toward the average
  position of local flockmates

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• Each boid has direct access to the whole scene's
  geometric description, but flocking requires that
  it reacts only to flockmates within a certain
  small neighborhood around itself.
• The neighborhood is characterized by a distance
  (measured from the center of the boid) and an
  angle, measured from the boid's direction of
  flight.
• Flockmates outside this local neighborhood are
  ignored. The neighborhood could be considered a
  model of limited perception (as by fish in murky
  water) but it is probably more correct to think
  of it as defining the region in which flockmates
  influence a boids steering.

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Reynolds Boids Movie
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Reynolds Boids Page

• http//www.red3d.com/cwr/boids/
• http//www.red3d.com/cwr/boids/

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• In cooperation with many coworkers at the
  Symbolics Graphics Division and Whitney / Demos
  Productions, we made an animated short featuring
  the boids model called Stanley and Stella in
  Breaking the Ice. This film was first shown at
  the Electronic Theater at SIGGRAPH '87. There was
  a technical paper on boids published at the same
  conference. In the course notes for SIGGRAPH '88
  there was an informal paper about obstacle
  avoidance.

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• Note that the straightforward implementation of
  the boids algorithm has an asymptotic complexity
  of O(n2). Each boid needs to consider each other
  boid, if only to determine if it is not a nearby
  flockmate. However it is possible to reduce this
  cost down to nearly O(n) by the use of a suitable
  spatial data structure which allows the boids to
  be kept sorted by their location. Finding the
  nearby flockmates of a given boid then requires
  examining only the portion of the flock which is
  within the general vicinity. Using such
  algorithmic speed-ups and modern fast hardware,
  large flocks can be simulated in real time,
  allowing for interactive applications.

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Steering Behavior for Autonomous Characters

• Abstract This paper presents solutions for one
  requirement of autonomous characters in animation
  and games the ability to navigate around their
  world in a life-like and improvisational manner.
  These "steering behaviors" are largely
  independent of the particulars of the character's
  means of locomotion. Combinations of steering
  behaviors can be used to achieve higher level
  goals (For example get from here to there while
  avoiding obstacles, follow this corridor, join
  that group of characters...) This paper divides
  motion behavior into three levels. It will focus
  on the middle level of steering behaviors,
  briefly describe the lower level of locomotion,
  and touch lightly on the higher level of goal
  setting and strategy.

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Steering Behavior Web Site

• http//www.red3d.com/cwr/steer/
• http//www.red3d.com/cwr/steer/
• So run the behavior demos point students
  towards OpenSteer web site
• http//opensteer.sourceforge.net/
• http//opensteer.sourceforge.net/

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Other Papers to Read

• http//www.aiwisdom.com/bytopic_flocking.html
• http//www.aiwisdom.com/bytopic_flocking.html