is an artificial life
Artificial life is a field of study and an associated art form which examine systems related to life, its processes, and its evolution through simulations using computer models, robotics, and biochemistry. The discipline was named by Christopher Langton, an American computer scientist, in 1986...
program, developed by Craig Reynolds
Craig W. Reynolds , is an artificial life and computer graphics expert, who created the Boids artificial life simulation in 1986. Reynolds worked on the film Tron as a scene programmer, and on Batman Returns as part of the video image crew. He is the author of the OpenSteer library.-External...
in 1986, which simulates the flocking
Flocking behavior is the behavior exhibited when a group of birds, called a flock, are foraging or in flight. There are parallels with the shoaling behavior of fish, the swarming behavior of insects, and herd behavior of land animals....
behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM
The Association for Computing Machinery is a learned society for computing. It was founded in 1947 as the world's first scientific and educational computing society. Its membership is more than 92,000 as of 2009...
SIGGRAPH is the name of the annual conference on computer graphics convened by the ACM SIGGRAPH organization. The first SIGGRAPH conference was in 1974. The conference is attended by tens of thousands of computer professionals...
conference. The name refers to a "bird-like object", but its pronunciation evokes that of "bird" in a stereotypical New York accent.
As with most artificial life simulations, Boids is an example of emergent
In philosophy, systems theory, science, and art, emergence is the way complex systems and patterns arise out of a multiplicity of relatively simple interactions. Emergence is central to the theories of integrative levels and of complex systems....
behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:
- separation: steer to avoid crowding local flockmates
- alignment: steer towards the average heading of local flockmates
- cohesion: steer to move toward the average position (center of mass) of local flockmates
More complex rules can be added, such as obstacle avoidance and goal seeking.
The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata et al.
extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes
introduced a complementary force to the alignment that they call the change of leadership. This steer deﬁnes the chance of the boid to become a leader and try to escape.
The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.
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. It was for instance used in the 1998 video game Half-Life
for the flying bird-like creatures seen at the end of the game on Xen, named "boid" in the game files.
At the time of proposal, Reynold's approach represented a giant step forward compared to the traditional techniques used in computer animation for motion pictures. The first animation created with the model was 1987's (Stanley and Stella in) Breaking the Ice
Stanley and Stella in: Breaking the Ice, also known as Love Found is a 1987 computer animated short film.- Synopsis :Birds and fish are moving around different halves of a sphere, separated by a sheet of ice. One bird and one fish notice each other and approach their sides of the ice sheet...
, followed by a feature film debut in Tim Burton's film Batman Returns
Batman Returns is a 1992 American superhero film directed by Tim Burton. Based on the DC Comics character Batman, it is the sequel to Burton's Batman , and features Michael Keaton reprising the title role, with Danny DeVito as the Penguin and Michelle Pfeiffer as Catwoman.Burton originally did not...
with computer generated bat swarms and armies of penguins marching through the streets of Gotham City .
The boids model has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations
. It has also been used for visualizing information
and for optimization tasks