Boids and Autonomous Agents


︎︎︎ WETA
︎︎︎ Autonomous Vehicles

In 1987, Craig Reynolds, an AI and computer graphics researcher, introduced “boids,” a program that simulates complex flocking motions—the collective motion of self-propelled entities like birds—using simple rules that would allow each “boid” to act as an independent agent.

The complex flocking motion that resulted from these simple rules surprised both Reynolds and the computer graphics community. “Boids,” and the creation of emergent complex motion through the application of relatively simple rules to large numbers of autonomous agents, became an influential concept that was adopted and extended by many researchers, software developers and special effects artists.

Are “boids” really artificial intelligence, or simply clever algorithmic constructions that produce the illusion of complex behaviour without any underlying understanding? It is a subject of some debate, yet the same question can be asked of any AI system. Recalling Alan Turing’s “Imitation Game,” it may be sufficient to say that animating with autonomous agents creates the illusion of life on a grand scale—one that has fooled even expert human observers.

The three rules (or steering behaviours) for “boids” were simple:

  • separation: steer to avoid crowding local flockmates
  • alignment: steer toward the average heading of local flockmates
  • cohesion: steer to move toward the average position (centre of mass) of local flockmates

“Boids” was first presented by Craig Reynolds in 1986 as a technical paper at SIGGRAPH, the prestigious annual computer graphics conference. In 1987, Reynolds premiered a short computer animated film, Stanley & Stella, which featured a flock of birds and a school of fish animated using the “boids” algorithm. In 1998, Reynolds was honored with an Academy of Motion Pictures Scientific and Technical Award in recognition of “his pioneering contributions to the development of three-dimensional computer animation for motion picture production.”

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Craig Reynolds, Boids Demo, 1987, Courtesy of the Artist