| Window | All objects within a rectangle that you specify by picking two points |
| Last | The last object you drew that’s still visible in the drawing area |
| Crossing | All objects within or crossing a rectangle that you specify by picking two points |
| ALL | All objects on layers that aren’t frozen and that are in the current space (model space or paper space) |
| Fence | All objects touching an imaginary polyline whose vertices you specify by picking points |
| WPolygon | All objects within a polygonal area whose corners you specify by picking points |
| CPolygon | All objects within or crossing a polygonal area whose corners you specify by picking points |
| Previous | The previous selection set that you specified |
To use any of the command-first selection options at the Select objects prompt, type the uppercase letters corresponding to the option and press Enter. After you’re finished selecting objects, you must press Enter again to tell AutoCAD that you’ve finished selecting objects and want to start the editing operation.
The following example demonstrates how to use the Erase command in command-first mode with several different selection options. The selection techniques used in this example apply to most AutoCAD editing commands:
1. Press Esc to make sure that no command is active and no objects are selected.
If any objects are selected when you start an editing command, the command in most cases will operate on those objects (selection-first editing) instead of prompting you to select objects (command-first editing). For the reasons that I describe earlier in this chapter, you should use the command-first editing style until you’re thoroughly familiar with it. Later, you can experiment with selection-first editing if you like. (Just reverse the sequence of commanding and selecting that I describe in this chapter.)
2. Click the Erase button on the Modify toolbar.
The command line displays the Select objects prompt.
3. Select two or three individual objects by clicking each one.
AutoCAD adds each object to the selection set. All the objects you select remain ghosted. The command line displays the Select objects prompt.
4. Specify a bounding selection box (Window) that completely encloses several objects.
Move the cursor to a point below and to the left of the objects, click, release the mouse button, move the cursor above and to the right of the objects, and click again.
All objects that are completely within the box are selected.
5. Specify a crossing selection box (Crossing) that encloses a few objects and cuts through several others.
Move the cursor to a point below and to the right of some of the objects, click, release the mouse button, move the cursor above and to the left of some of the objects, and click and release again.
All objects that are completely within or cross through the box are selected.
6. Type WP and press Enter to activate the WPolygon selection option.
The command line prompts you to pick points that define the selection polygon.
7. Pick a series of points and press Enter.
Figure 6-3 shows an example. After you press Enter, AutoCAD selects all objects that are completely within the polygon.
8. Press Enter to end object selection.
AutoCAD erases all the selected objects.
Notice how you were able to use a combination of object selection methods to build up a selection set and then press Enter to execute the command on them. Most AutoCAD editing commands work this way in command- first mode.
If, after erasing a selection set, you immediately realize that you didn’t really mean to do away with so many objects, you can use the Undo button on the Standard toolbar to restore all of them. But AutoCAD has one additional un-erase trick up its sleeve — the aptly named OOPS command. When you type OOPS and press Enter, AutoCAD restores the last selection set that you erased — even if you’ve run other commands after Erase.
Figure 6-3: Lasso-ing objects with a WPolygon.
Ready, Get Set, Edit!
The following sections cover the most important AutoCAD editing commands, using command-first editing mode.
Whether you start an AutoCAD editing command by clicking a toolbar button, choosing a pull-down menu command, or typing a command name, in almost all cases the command prompts you for points, distances, and options at the command line. Read the command line prompts during every step of the command, especially when you’re figuring out how to use a new editing command. Otherwise, you’re unlikely to complete the command successfully.
As I describe in Chapter 4, maintaining precision when you draw and edit is crucial to good CAD work. If you’ve used a drawing program and are accustomed to moving, stretching, and otherwise editing objects by eye, you’ll need to suppress that habit when you edit in AutoCAD. Nothing ruins a drawing faster than approximate editing, in which you shove objects around until they look okay, without worrying about precise distances and points.
