1 Background

In conventional animation techniques an animation is simply a sequence of pictures, frames , that are displayed in quick succession. For interactive animation and simulation, this is not enough. It is useful to consider the scene as composed of objects that each have a more or less autonomous behaviour. For this reason, we developed an obect-oriented animation system, supported by a an object-oriented scripting language. This GDP system (Generalized Display Processor) and language LOOKS are implemented at our department and are used for numerous applications, varying from algorithm animations to simulation of mechanical systems.

One of the key features of this animation system is the simulation of rigid body dynamics. Objects move according to the laws of physics, taking into account relevant magnitudes such as mass, momentum, force. As such, rigid body objects form a salient example of components with both a well-defined interface and an autonomous behaviour.

Thus, screen objects are relatively autonomous, displaying a behaviour of their own, though still subject to interactions. This makes the study of these objects as software components particularly interesting.