>On Tue, 8 Jan 2002 17:53:31 -0700, Richard Bragg <[EMAIL PROTECTED]> wrote:
>Does anyone know how I could get just the lines along the outermost outline > of the entire polyhedron? What you are probably looking for are silhouette edges. Can be done using a stencil buffer. Using software, you can try to identify the "hard edges" in your polyhedron and render them separately in a LineGeoemtry. Hard edges are those that neighbor polyhedra whose normals deviate from each other by more than the "crease angle". At the vertices belonging to such edges, the normals are actually multi-valued. Java3D's normal generator does identify such vertices and creates non-unique normals where necessary, but the edges themselves are not available as output. As a typical example, if you have a cube discretized with many tris or quads, the the sharp edges that you see is because Java3D generates multi-valued normals at the vertices of the edge. It is these edges that you want to isolate and grab for rendering the outline of the polyhedral dataset. This approach will also be able to identify the outline edge between the flat circular face and the curved surface of the cylinder. However, the above methodology will not work for the curved surface of a cylinder (assuming that the cylinder has been tesselated fine enough ) because there are simply no real hard edges. A more complicated twist to your example is if you also need to have the "vertical lines" of your curved surface always snapping back to face the viewer and at the same maintaining the correct diametral distance between them. For the curved surface, there is no automatic way of determining the outline edges, unless you provide them. If your geometry is 2-D manifold, then you could simply grab the boundary edges - edges which have only one polygon neighbor - for getting your outline. Regards Raj Vaidya =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
