AI for Game Developers

Chapter 4. Flocking

Often in video games, nonplayer characters must move in cohesive groups rather than independently. Let’s consider some examples. Say you’re writing an online role-playing game, and just outside the main town is a meadow of sheep. Your sheep would appear more realistic if they were grazing in a flock rather than walking around aimlessly. Perhaps in this same role-playing game is a flock of birds that prey on the game’s human inhabitants. Here again, birds that hunt in flocks rather than independently would seem more realistic and pose the challenge to the player of dealing with somewhat cooperating groups of predators. It’s not a huge leap of faith to see that you could apply such flocking behavior to giant ants, bees, rats, or sea creatures as well.

These examples of local fauna moving, grazing, or attacking in herds or flocks might seem like obvious ways in which you can use flocking behavior in games. With that said, you do not need to limit such flocking behavior to fauna and can, in fact, extend it to other nonplayer characters. For example, in a real-time strategy simulation, you can use group movement behavior for nonplayer unit movement. These units can be computer-controlled humans, trolls, orcs, or mechanized vehicles of all sorts. In a combat flight simulation, you can apply such group movement to computer-controlled squadrons of aircraft. In a first-person shooter, computer-controlled enemy or friendly squads can employ such group movement. You even ...