ARTS 102 Aesthetics of the Algorithmic Image


Johannes Goerz



Flocking behaviour

The idea of flocking was derived from the nature. By regarding animals which move in groups special patterns of behavior can be observed, like flocking birds, swarms of insects or schools of fishes.
Through the behavior of each individual within the group, which is determined by simple rules, a complex motion behavior of the group emerges. This phenomenon is called emergent behavior.

Boids is a program to simulate emergent behavior of flocking animals. It was developed by Craig Reynolds in 1986.
The behavior of the animals (also called agent or boid) is defined by a simple set of rules. Every agent is following exatly the same set of rules which leads to complex motion and interaction of the flock.

Craig Reynolds described the movement through three simple steering behaviors which are based on positions and velocities of nearby flockmates. They govern the behavior of each individual agent.

Alignment

Turning the moving direction to the same as the local flockmates.

Boids try to match velocity with near boids.
The alignment is represented by the agent's velocity vector. By averaging the nearby agent's vectors the velocitiy and alignment of the agent will be the average of it's surrounding boids.

Seperation

Keeping distance to the nearby flockmates to avoid collisions.

Boids try to keep a small distance away from other objects and boids.
Whenever one boid is too close to another the distance between them gets increased.

Cohesion

Steer to move toward the average position of local flockmates.

Boids try to fly towards the centre of mass of neighbouring boids.
The "center of mass" is the average position of the nearby flockmates. It is gained through averaging the surrounding boids' position vectors.

Beside these three basic rules, more complex rules, such as obstacle avoidance and goal seeking, can be added to achieve a more realistic simulation.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals. The 1992 Tim Burton film Batman Returns was the first movie to feature animated animals (bat swarms and an army of penguins) using the boid model.

3D Boids by Conrad Parker

Craig Raynold's Boids
Wilensky, U. (1998). NetLogo Flocking model
Conrad Parkers's Boid Page