Precise object interactions using solid modeling techniques

The great potential provided by the existing 3D hardware and software provide us the tools for modeling and displaying complete 3D physical objects in computer systems. Despite the advanced ability to create and display 3D objects, there is a lack of interaction techniques by which the user can intuitively manipulate these 3D objects and perceive information about them. GIVEN (Gesture-driven Interactions in Virtual ENvironments) is a 3D interaction toolkit which aims at aiding in the development of new 3D interaction and dialogue techniques. The user of the GIVEN toolkit is not dealing any more with a picture of an object. He can directly manipulate 3D objects using 3D input devices, such as spaceball and dataglove, for grabbing, pushing and moving them. With our first application, for virtual environments, we found out that very unnatural object interactions happen if the collision detection, necessary for the interaction, is made by using only bounding volumes. Precise object interac tions are required to let users grab, push and position objects precisely in a 3D world. For this purpose, a boundary representation was integrated to be used for the implementation of an advanced collision detection scheme. This paper describes an algorithm for performing the intersection of two polyhedra. New preprocessing algorithms are explained in detail that speed up on avrage the overall performance of the intersection algorithm. Robustness is achieved by propagating all topological information immediately to the neighbor faces. The application of this algorithm inside GIVEN is also presented.