Boids: Flocking Behavior

CS 482 Lecture, Dr. Lawlor

Back in 1986, Craig Reynolds wrote a good SIGGRAPH paper on simulating flocks of birds, which he called "Boids".

This replaces the complexity of actual bird brains with three simple vectors:

Separation: if you're too close to a neighbor, steer away from them.
Alignment: adjust your velocity towards the average velocity of your neighbors. This keeps the flock moving in the same direction.
Cohesion: move toward the average position of your neighbors. This keeps the sides of the flock from becoming ragged.

Note that in each case, we only perform local interactions with nearby neighbors, but the global effect is for the boids to respond coherently as a single mass.

See my Boids / flocking example.

In real life, flocks of starlings create strikingly similar patterns. Schools of sardines are similar, except they also scatter en masse to avoid predators such as sharks or diving birds.