3D AutoCAD Basics

Viewing
1. 3D Orbit
   The easiest way to view in 3D is to use the 3dorbit command or the 3d Orbit toolbar. Right-click in 3dorbit mode gives you options on projection, shading and some other visual aids.
2. Shading
   To change the way AutoCAD changes the shade mode, use the shademode command or the Shade toolbar.
3. Viewports
   Use the vports command or the Viewports toolbar to split your screen into multiple views.
4. Views
   After creating a view, you may want to save it. Use the view command or the View toolbar to save your views. The View toolbar also provides icons for some predefined views. The elevational views alter the ucs. The isometric views do not. The plan command can change the current view of the drawing so that it is perpendicular to the current ucs or the wcs.

Coordinate Systems

1. WCS - World Coordinate System
   A coordinate system used as the basis for defining all objects and other coordinate systems.
2. UCS - User Coordinate System
   A user defined coordinate system. The user can only draw on the xy plane of the current UCS. To draw on another plane, the UCS must be changed. To alter the UCS, use the ucs command.
3. UCS command
   The ucs command comes with many options but some of the more useful ones are 3point, origin and world. 3point defines a new ucs given 3 points which correspond to the origin, a point on the x-axis, and a point on the y-axis. Origin moves the origin point (0,0,0) of the UCS to the designated point. World changes the UCS to match the WCS which is commonly used method to reset the UCS.
4. UCS icon
   The ucsicon command controls how the ucs icon is displayed on the screen.

Solids
1. Extrude
   The most common method to create solids is to use the extrude command and extrude a solid from a closed pline. The original pline will become the new solid which will be created on teh current layer. A couple of things you should be aware of when doing this: 1) Make sure all your corners are closed by using object snaps. If the pline is not closed, the extrusion will not work. 2) Make sure the pline does not overlap itself. This will generate solids with extra lines and have potential problems when exporting to other programs. 3) If, after all your efforts to fix a pline, it still doesn't work, it's usually best to start over and trace a new pline.
2. Solid Objects
   box, sphere, cylinder, cone, wedge, torus.
3. Solid Display
   Sometimes a solid in AutoCAD looks like a bunch of lines as opposed to a solid object. To increase the number of lines used to represent a solid, use the isolines command and increase the number. The higher the number, the more lines used and the longer it takes to display the object.
4. Solid Editing
   Union, Subtraction, Intersection, Slice, Revolve, with the Solid and Solids Editing toolbar.

Relationship between LINES, PLINES, SOLIDS, and SURFACES