CompuServe Messages

Michael – Good point about the "true edge." Not only may that happen in 2d, it does happen in 3D. However, the more segments you call for, the closer to a "true edge" you are going to get. Also, if you pick the correct number of segments, and the correct viewing angle, you should be able to get a true-edge line. The "correct number of segments" is either an odd number or an even number (don't ask me which) – but it is the number which puts the joint between adjacent facets at the perimeter of the shape. Say you were looking at a sphere head-on. An even number of facets (say 32) puts 16 on one hemisphere and 16 on the other. Looking at that head-on, you see the true edge (polluted somewhat by the facets going the other way). It depends how accurate you need the image to be. Removing hidden lines does not solve the problem. A true edge is not substituted for the faceted one. Your idea of tracing the edge may be the ticket. After creating the image in 3D and importing it into 2D, you can use the "C" command in DCAD to create a curve around the perimeter by selecting the apex of each visible facet. Then erase the facets. You have revealed a very interesting problem for all drawing programs. The escape hatch for all is the rendering, which smooths the whole shape, but which now, on thinking about your point, may not reveal the true edge either. I guess it depends on how accurate your image has to be. Is the problem associated with the dimensioning of your shapes or the appearance of the shapes? Let me know how it goes. — gtm —