Chapter 5: Flocking

During early summer evenings, you have probably seen flocks of birds flying in the sky. You have probably noted how they seem to move as a single living object: they all move in a particular direction, turn around, and grow and shrink. A flocking system aims to replicate this behavior in games: we want to implement an algorithm to move many objects as an organic group.

In games, we call each element of a flock a boid. To implement a flocking behavior, we do not need to equip each boid with a high-level complex decision-making system; instead, all we need to do is implement simple reactive rules for each boid that depend only on the state of the flock itself. Thus, flocking is an excellent example of emergent behavior: each boid reacts exclusively to its neighbor's behaviors; nevertheless, the flock seems to move as if someone were coordinating it.

In this chapter, we will learn what these rules are and how to implement them in Unity3D. We will implement...