During the last lesson of complex systems course, prof. Vizzari showed a crowd simulation based on BOIDS, an intriguing model invented by Craig Reynolds in 1986 that simulates bird flocks, fish schools and all that kind of self-organizing masses of living stuff. The basic model is based on three simple assumptions:
- each boid moves toward the other flockmates (cohesion)
- each boid moves away from crowded situations (separation)
- each boid follows the direction of the rest of the flock (alignment)
There exist several approaches to crowd simulation (like cellular automata or multi-agent systems) but I do think that BOIDS have many interesting capabilities.
In fact, one of the open issues in crowd simulations is the sponteneous formation of groups because of common goals, shared costumes, socio-political aspects, familiar relationships and so on. BOIDS leave a lot of space for embedding this wide spectrum of behaviours, whilst the model itself mantains the proxemic distances between people and let them gather peacefully, by the rules decribed above.
The video I embed shows my model in a simple scenario made of four groups (yellow, red, green and blue). Green people have their own goal to follow; red and blue have a shared one. Yellow people just walk around the space, with no specific purpose. In the middle of the screen there's a strong repulsor which keeps boids away. The dynamic works as I expect: there's the formation of clusters, boids belonging to the same group tend to aggregate and find their way even in overcrowded situations. What's fascinating is the emerging, unexpected behaviour of yellow ones: some of them hold still, some dodge the crowd, many other enter the moving groups and follow them wherever they go, conditioned by the first rule.Very nice.
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one the most interesting scenario to simulate