Motion Control of Synthetic Actors: an Integrated View of Human Animation

This paper explains the ideal concepts that must be part of a system for synthetic actor animation. After a brief introduction to the role of synthetic actors, five major steps to the motion control of these actors are discussed: positional constraints and inverse kinematics, dynamics, impact of the environment, task planning and behavioral animation. 1. The synthetic actor approach Three-dimensional human modeling and animation have existed for more than 15 years [Badler,1982; Magnenat-Thalmann and Thalmann, 1985]. However emphasis has been placed on separate aspects of this animation. For example, a great deal of research has been done on the modeling and animation of the body [Badler and Smoliar, 1979; Kroyer, 1986; Forest et al. 1986], on facial animation [Parke, 1974; Platt and Badler, 1981; Pearce et al., 1986; Hill et al., 1988; Lewis and Parke, 1987; Waters, 1987; Magnenat-Thalmann et al., 1988b] and hand animation [Catmull, 1972; Badler and Morris, 1982; Magnenat-Thalmann et al. 1988]. More recently, researchers have incorporated mechanical aspects factors into the animation of articulated bodies [Armstrong and Green, 1985; Armstrong and Green, 1985b; Wilhelms and Barsky, 1985; Wilhelms, 1987; Girard, 1987; Isaacs and Cohen, 1987]. Also task level factors have been studied by several researchers [Zeltzer, 1982; Zeltzer, 1985; Badler et al., 1985; Badler et al. 1987]. Other authors have tried to animate more realistic characters, from an image synthesis point of view, but using primitive methods like rotoscopy or image-based keyframe animation. The synthetic actor approach corresponds to an integration of all methods, allowing the creation of 3D characters, with the appearance of real human characters. Ideal synthetic actors should satisfy the following criteria: they should have the appearance of real persons their behavior should be similar to that of real persons they should have their own personality: two different actors should have different personalties, i.e. different reactions to the same situation