2 Boundary Computation of Csg Models with Nurbs Primitives

We present eecient and accurate algorithms for Boolean combinations of solids composed of sculptured models. The boundary of each solid is represented as a collection of trimmed spline surfaces and a connectivity graph. Based on algorithms for trapezoidation of polygons , partitioning of polygons using polygonal chains, surface intersection of high degree spline surfaces and ray-shooting, the boundaries of the resulting solids and its connectivity graph after the Boolean operation are computed. We also present accurate representations of the intersection curves and boundary of the resulting solids. The resulting boundaries are used for interactive display and walkthrough applications. The system has been used to convert parts of a submarine storage and handling system model represented as more than 2; 000 CSG trees. The B-rep consists of more than 30; 000 trimmed spline surfaces and is displayed at interactive rates on the Pixel-Planes 5 graphics system.