Instead they may effectively play out their roles by reacting to internal and external influences in ways that are both predictable and consistent with the scenario for which they were designed. In the process of learning to build these types of characters we have often found ourselves struggling with two fundamental problems. 2 Expectations of a Synthetic Character To learn how to build believable characters we look back upon the rich history of traditional character animation. When looking at a character brought to life by one of the great masters we know exactly what that character is thinking and feeling at every instant and, while we may not know exactly what it is about to do, we can always call upon our perception of its desires and beliefs to hazard a guess. The American philosopher Daniel Dennett believes that they work because, in order to understand and predict the behavior of the animate objects around them, people apply what he calls the intentional stance .
Desires are the key to identifying with and understanding a character.
We understand the actions of characters by inferring how their beliefs influence the ways they attempt to satisfy their desires. 2.1 Motivational Drives For a character to appear properly motivated it must continue to work towards satisfying its desires while gracefully handling unexpected situations. By biasing action selection towards behaviors that will satisfy the internal needs of the character, motivational drives provide a way to achieve goal-oriented behavior. Most approaches agree on the general behavior of drives. These desires can be attended to by the successful execution of attentive behaviors like eating, or by changes in external stimuli, such as temperature fluctuations or interactions with other characters.