In Book V, Chapter 5, I covered creating and modifying 3D solids. This chapter takes a similar look at creating and modifying surfaces, faces, and meshes. Many commands allow you to create primitives out of surfaces rather than a 3D solid. You can also create complex 3D surfaces by starting with 2D objects and performing extruding and revolving operations to create a new surface model. Surfaces, faces, and meshes take a little more planning to create and modify than 3D solids do, but they do have advantages, depending on what you are trying to model.
AutoCAD offers a variety of commands that allow you to create primitives as surfaces, which are similar to the commands that allow you to create primitives as 3D solids. Just like the primitive 3D solids, surfaces help to form the foundation of 3D modeling in AutoCAD. Surfaces are not as easy to modify as 3D solids, but you can deform and change their shape much easier than you can a 3D solid. Most of the primitives that can be created as 3D solids can be created with surfaces through the use of the 3D command or a command designed to create a specific type of primitive object. You can also create faces and free-form meshes when creating a surface model. Table BC1-1 lists the commands that are used to create surfaces, faces, and meshes for surface models.
Table 1.1. AutoCAD's Surface Modeling Commands
Command Name (Alias)