Today’s video games feature synthetic characters involved in complex interactions with human players. A synthetic character may have one of many different roles: a tactical enemy, a partner for the human player, a strategic opponent, a simple unit among many, or a substitute for the player when he or she is unavailable.
In all of these cases, the game developer’s ultimate objective is for the synthetic character to act as if it were controlled by a human player. This implies the illusion of spatial reasoning, memory, commonsense reasoning, using goals, tactics, planning, communication and coordination, adaptation, unpredictability, and so on. In current commercial games, basic gesture and motion behaviours are generally satisfactory. More complex behaviours usually look much less lifelike. Sequencing elementary behaviours is an especially difficult problem, as compromises must be made between too-systematic behaviour that looks automatic and too-random behaviour that looks ridiculous.