Virtual Actors now play an important role in computer-generated films, Virtual Environments, Telecooperative work, and multimedia. In order to make these actors realistic, it is essential to represent their body shape during the motion. In this paper we present different methods for representing realistic deformations for virtual humans with various characteristics: sex, age, height, weight. Our methods based on a combination of metaballs and splines could be applied to frame-by-frame computer generated-films and Virtual Environments. Several examples are presented: autonomous actors, animation based on flock of birds, networked Virtual Environments