Group Behaviours

Group behaviours are steering behaviours where some or all other moving entities are taken into consideration. Flocking is probably the best known group behaviour (developed by Craig Reynolds in 1986) it was used in the 1992 film Batman Returns to simulate bat swarms.

Flocking is a combination of three group behaviours cohesion, separation and alignment. When calculating the steering forces only moving entities within a certain distance (neighbourhood radius) of the vehicle is considered. The neighbourhood is shown as grey circles in this diagram.

Separation

This produces steering forces that will move the vehicle away from it's neighbours.

Alignment

This attempts to keep the vehicle aligned to the average heading of it's neighbours.

Cohesion

This produces steering forces that moves the vehicle towards the centre of mass of it's neighbours.

Flocking

Although separation, cohesion and alignment can be used individually they are usually used in combination to create swarming effects.