This paper aims to present an approach to model crowd motion in normal and panic situations in order to study the influence of the individual's decision on a crowd situation. Different aspects of the human behavior are modelled for example the individual and group strategy for evacuation, the negotiation strategy in a blocked situation and the spreading of panic into the crowd. This approach is based on the Individual Based Model (IBM) to study and simulate the complex system such as the social system of crowd motion, and presents another way to study the special spreading of panic into the environment. The prototypes produced by our approach for crowd simulation in a virtual environment illustrate the importance of the individual's decisions within the crowd and show how disruption affects the efficiency of evacuation.