outlining of spline surface about a year ago i started work on a problem that appeared to be very simple and turned out to be quite difficult i am wondering if anyone on the net has seen this problem and hopefully some published solutions to it the problem is to draw an outline of a surface defined by two roughly parallel cubic splines for inputs the problem essentially starts with two sets of points where each set of points is on the edge of an object which we treat as two dimensional i e only extant between the edges but which exists in three dimensional space to draw the object we fit a cubic spline through the points each spline is effectively computed as a sequence of line segments approximating the curve each spline has an equal number of segments we assume that the nth segment along each spline is roughly but not exactly the same distance along each spline by any reasonable measure take each segment n along each spline and match it to the nth segment of the opposing spline use the pair of segments to form two triangles which will be filled in to color the surface depth sort the triangles take each triangle in sorted order project onto a d pixmap draw and color the triangle take the edge of the triangle that is along the edge of the surface and draw a line along that edge colored with a special edge color it is the edge coloring in step that is at the heart of the problem the idea is to effectively outline the edge of the surface the net result however generally has lots of breaks and gaps in the edge of the surface the reasons for this are fairly complicated they involve both rasterization problems and problems resulting from the projecting the splines if anything about this problem sounds familiar we would appreciate knowing about other work in this area thanks
