Discusses the role and the evolution of animation, simulation and scientific visualization and their relationships. Two trends are described: (1) the physical laws are well-known and their use improves the animation; (2) the physical laws are not really well-known and the animation techniques contribute to understanding them. The authors distinguish descriptive models used to reproduce an effect without knowledge about its cause and generative models describing the cause which produces the effects. Cooperation between descriptive and generative models is also discussed as well as man-machine interface constraints. Finally, the evolution of animation towards automatic motion control, goal-oriented motion, task modeling and behavioural animation is emphasized