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Case Study

An essential part of navigation is the ability to avoid obstacles successfully. This accounts for many of the properties previously described. It's also a good place to start learning about game AI development because obstacle avoidance is a relatively simple task.

To understand how obstacle avoidance works, it is worthwhile to analyze the behavior in different situations. The following list is a representative selection of all the possible states that the game character may encounter. For each scenario, the situation is briefly described and the desired outcome is explained (see Figure 6.3):

Figure 6.3. Three different situations that require three different kinds of responses, ranging from quick turnaround to straight forward movement.


  • When no obstacles are in proximity of the animat, it can move forward normally. This can be either straight, or a wandering behavior.

  • In the case where walls are detected on one side, they should be turned away from slowly, in a preventive fashion.

  • If there is an obstacle in front, a turn should be engaged to clear the danger on one side.

  • For those situations where the animat is stuck in a corner, a more radical turnaround should be attempted.

This list of expected actions, together with the four criteria of motion explained previously, forms the requirements for our obstacle-avoidance behavior.

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