This section introduces three techniques for creating 3D objects: drawing 3D lines and polylines, creating 3D objects from 2D geometry, and creating solids. (In AutoCAD LT you can use the first two techniques only.) AutoCAD is also very capable at surface modeling, offering both freeform mesh and NURBS surfaces. If you're interested in either of these, check out the online help system — navigate to User's Guide, then choose Work with 3D Models, and then Create 3D models. Topics include creating surfaces and meshes from scratch, and creating solids and surfaces from 2D objects.
When you draw 3D objects, just like when you draw 2D objects, put them on appropriate layers and use precision techniques to specify each point and distance. (See Chapter 5 for more information.)
The most basic forms of 3D geometry are wireframe-like objects created by picking points or entering X,Y,Z coordinates. Such objects have no surfaces, so look the same in 2D Wireframe mode or a photorealistic rendering. They are most useful as paths for sweeps and lofts, or as edges for surface creation. Such objects include