In many cases, the design of a surface does not require a grid of control points. For example, if we have the profile of a vase, then rotating the profile about a line would be sufficient to crease a vase (i.e., a surface of revolution). Many surfaces can be created in such a simple way. These include ruled surfaces, surfaces of revolution, swung surfaces, and swept surfaces. Moreover, if we have more profiles (i.e., the cross sections), we can also fit a surface that contains all profiles. This is the skinned surfaces. The design of these surfaces fit into a special technique, the cross-sectional design.
In general, the cross-sectional design technique requires one or more profile curves that describe the profile, or cross section, of the desired surface, and perhaps a trajectory curve that guides that way of sliding the profile curves. As the profile curves sliding along the trajectory curve, a surface is generated. Depending on the way of specifying profile and trajectory curves and the way of sliding the profile curves (perhaps with transformation), we have one of the five above mentioned types. The following pages will provide a description of how to generate these surface under the surface and curve subsystems of DesignMentor.
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Special note for Windows 95/98/NT users:
The Windows 95/98/NT version of the surface subsystem automatically start the curve subsystem to perform cross-sectional design. In fact, there is no Cross Sectional Design menu item at all. You have to start the curve subsystem manually. Then, use the curve subsystem to design profile and trajectory curves and export the result (to the surface subsystem). Finally, switch back to the surface subsystem and use File, followed by Load, followed by Load Cross Sectional Design. This would load the surface designed under the curve subsystem into the surface subsystem. |