DETERMINING INTERFERENCE BETWEEN PAIRS OF SOLIDS DEFINED CONSTRUCTIVELY IN COMPUTER ANIMATION

This paper presents theory and implementation of a method for detectin g interference between a pair of solid objects. Often at times, when p erforming simulations, two solids may unwittingly interpenetrate each other. The two components of the system presented in this paper are: ( 1) a surface representation method to model solid objects: and (2) a m ethod for detecting interference. Body representation of a solid in th is system is based upon enveloping each solid with surfaces (called po sitive entities). Most computer aided design (CAD) systems use solid m odeling techniques to represent solid objects. Since most solid models use Boolean operations to model complex objects, a method is presente d to envelop complex objects with parametric surfaces. ii method for t racing intersection cloves between two surfaces is also presented. Dis continuities on surfaces are defined as negative entities in older to extend the method to complex solids. Determining interference is based upon a numerical algorithm for computing points of intersection betwe en boundary curves and parametrized entities. The existence of segment s of these curves inside the boundary of positive and negative entitie s is established by computing the circulation of a function around the boundary curve. Interference between two solids is then detected. No limitations are imposed on the convexity or simplicity of the boundary curves treated.