An algorithm for silhouette of curved surfaces based on graphical relations

Abstract The proposed algorithm displays the projected surface Γ as a quadrilateral grid of straight segments, g; any one of these can be part of the silhouette if, and only if, the two patches connected along g lie on the same side of it. The same segment g is drawn, if it is not hidden by remote patches. The algorithm can be applied to any surface regular or not and self-intersecting and can display the entire silhouette or a part of it. It is simple, it uses only the rectangular coordinates of the projected vertices of the grid and requires few elementary mathematical operations.