Chapter 3. Pattern Movement

This chapter covers the subject of pattern movement. Pattern movement is a simple way to give the illusion of intelligent behavior. Basically, the computer-controlled characters move according to some predefined pattern that makes it appear as though they are performing complex, thought-out maneuvers. If you’re old enough to remember the classic arcade game Galaga, you’ll immediately know what pattern movement is all about. Recall the alien ships swooping down from the top and in from the sides of the screen, performing loops and turns, all the while shooting at your ship. The aliens, depending on their type and the level you were on, were capable of different maneuvers. These maneuvers were achieved using pattern movement algorithms.

Although Galaga is a classic example of using pattern movement, even modern video games use some form of pattern movement. For example, in a role-playing game or first-person shooter game, enemy monsters might patrol areas within the game world according to some predefined pattern. In a flight combat simulation, the enemy aircraft might perform evasive maneuvers according to some predefined patterns. Secondary creatures and nonplayer characters in different genres can be programmed to move in some predefined pattern to give the impression that they are wandering, feeding, or performing some task.

The standard method for implementing pattern movement takes the desired pattern and encodes the control data into an array or set ...

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