When creating AI for game characters, we want them to appear to behave in realistic ways. This is done by defining different behaviors that a character can do, such as walking, patrolling, attacking, or searching for something, as well as how the character reacts to different items or events in the game environment. In addition to defining a character's behaviors, we need to define when the different behaviors occur. For example, instead of just following a path, we might want the character to change behaviors at different times. This chapter will look at the most popular way to define behaviors and when they occur: behavior trees. We have already looked at behavior trees in the previous chapters, but here, we will go into more detail.

In this chapter, we will learn about: