Flocking System Breakdown

Flocking Systems | Boids | Geometric Flight | Flocking Behaviour | Collision Avoidance | Velocity Matching | Flock Centring | Examples | Steering Behaviours | Seek and Flee | Pursuit and Evasion | Arrival | Wander | Path Following | Wall Following and Containment

Geometric Flight

A fundamental part of the boid model is the geometric ability to fly. Motion of any flock type can be considered as a type of flying by glossing over the complexities of wing, fin or leg motion. In the case of land bound creatures the third dimension is constrained, so the creatures only flock in two dimensions.

Flocking motion is only concerned with moving a particle along an undefined curve in 3D (or 2D in the case of land bound creatures) space. Motion local to the creature such as wing motion, leg movement etc can be as complicated or as simple as the animator makes it, yet the flocking motion would remain unchanged.

Geometric flight is in fact as simple as moving the boid incrementally along its forward axis, and rotating it about its pitch and heading axis to make it steer. Steering also realigns the boid’s local forward axis with its forward direction.


For flying creatures, a turn is induced by a roll, in which the up vector rotates to one side. Because the up vector is rotated to one side, the lift vector has not only a vertical component, but also a horizontal one, which has the effect of mving the object towards that direction, and hence inducing a turn.

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