Computing characteristic views of quadric-surfaced solids

An algorithm is presented for computing the characteristic views (CVs) of quadric-surfaced solids. The CVs are determined by analyzing the characteristic-view domains of the object by relating changes in the topology of the object´s line structure to changes in the occlusion of 3D edges. The main task of the algorithm is to compute the envelope boundaries for viewpoint regions for which the object´s visible-line projections have topologically equivalent line-junction graphs. By using the concepts of generalized edge, generalized face, and generalized vertex and using the techniques of order-of-visibility propagation and edge classification, the algorithm can efficiently compute both local and global visibility of edge segments, and therefrom compute the required envelope boundaries. This algorithm is shown to hold for quadric-surfaced solids in general and to treat a polyhedral object as a special case