Craig Reynolds’ flocking boids
This is a still from a 2D version of the famous flocking simulation, where the individual boids follow only three simple rules: separation, alignment and cohesion. I researched this and other ways of simulating interaction among many agents for a work designed to track human interactions, which (after much proposal-writing and discussion with potential collaborators) was abandoned for various reasons.
In the original you add new ‘boids’ by clicking in the window.
Java no longer works in browsers so there’s no interaction, but you can run the .pde code in Processing.
View source code. From a Processing example.