- Introduction
- Creating a New Drawing
- Model Space and Layout Space
- Communicating with AutoCAD
- Object Snaps, Ortho Mode, and Polar Tracking
- Undo/Redo
- Grid and Snap
- Draw a Circle
- Navigating Around the Drawing
- Object Properties
- Layers
- Dimension Styles
- Dimensioning
- Modifying Drawing Objects
- Grip Editing
- Introduction to Advanced Editing Techniques
- Cleaning Up Layout Space
- Plotting and Page Setups
- Chapter Summary
- Chapter Test Questions
This chapter is from the book
This chapter is from the book
This chapter is from the book
Modifying Drawing Objects
So far, we’ve looked at modifying object properties through the Quick Properties palette. One of the most powerful benefits of CAD systems is their unique ability to make changes to your drawing. This section introduces you to some of the basic tools used to modify your drawing.
Selection Sets
As with the drawing tools, AutoCAD has a general process for modifying objects:
Select an editing tool.
Specify which object(s) you want to modify.
Read the prompt.
Specify points and answer prompts.
Press <Enter> or <Esc> to end the command.
The process of specifying which objects you want to edit is called building a selection set.
It is possible to preselect the objects you want to modify. If any objects are selected prior to starting a command, AutoCAD will use these objects as the selection set and will skip the Select objects: prompt.
EXERCISE 2-18 MOVING OBJECTS
Make sure the Object Snap and Polar Tracking toggles on the status bar are turned on.
Select the Home tab of the ribbon so you can access the Modify panel.
Choose the Move tool from the Modify panel on the Home tab of the ribbon. AutoCAD prompts you to Select objects:.
Select the circle. AutoCAD again prompts you to Select objects:.
Select the two centerlines and press <Enter> to stop the selection process. AutoCAD prompts you to Specify base point or 
.
Move the cursor near the edge of the circle. When the Center object snap appears, pick that point to specify the center of the circle. AutoCAD starts dragging the objects from the center of the circle and prompts you to Specify second point of displacement or <use first point as displacement>:.
Drag the object straight up until the 90° polar tracking alignment path appears (see Figure 2-39). Once it appears, type 2<Enter>. The circle, lines, and dimensions move up 20.
)
FIGURE 2-39 Moving objects
Save your drawing.
When you started the MOVE command, AutoCAD needed to know which objects you wanted to move. The Select objects: prompt repeated until you pressed <Enter>, telling AutoCAD you had finished selecting objects. Once you finished selecting objects, AutoCAD then went on to complete the command. It asked you to specify where you wanted to move the objects from (the base point) and where you wanted to drag the objects to (the second point).
Notice that even though you didn’t select the dimension, it moved as well. This is because of the associativity of the dimension with the circle.
Now, let’s look at selecting the objects you want to modify first and then selecting the modify command.
EXERCISE 2-19 SELECTING FIRST
Pick a point on the screen above and to the right of the circle (point 1 in Figure 2-40). AutoCAD will prompt you: Specify opposite corner or .
Move the cursor down and to the left of the circle. AutoCAD will display a dashed rectangle with a green background from the first point you picked (see Figure 2-40). This is called a crossing window.
)
FIGURE 2-40 Creating a crossing window
Pick a point below and to the left of the circle (point 2 in Figure 2-40). AutoCAD will select all the objects that are inside or touch the edge of the crossing window you picked.
Choose the Erase tool from the Modify panel. AutoCAD immediately erases the selected objects.
Choose the Undo tool from the Quick Access toolbar to bring the objects back.
Save your drawing.
Notice that AutoCAD did not prompt you to select objects. Because you selected the objects before you started the command, AutoCAD assumed that those were the objects you wanted to erase. AutoCAD doesn’t care whether you select the objects before or after you start the command. If no objects are selected, AutoCAD will simply ask you to select them before it continues with the command.