Copyright Goodheart-Willcox Co., Inc.
176
AutoCAD and Its Applications—Advanced
setting was initially set to
Record
before performing two Boolean subtraction opera-
tions. The
Show History
property is currently set to
No
and the
Conceptual
visual style
is set current. In Figure 8-3B, the
Show History
property is set to Yes. Isolines have
also been turned on. You can see the geometry that was used in the Boolean subtrac-
tion operations. Using subobject editing techniques, the individual geometry can be
selected and edited. In Figure 8-3C, the sphere (the subtracted object) is selected while
pressing the
[Ctrl]
key. Selecting the sphere in this manner selects the solid primitive
subobject and displays a grip tool for editing the subobject. Using grip tools for editing
3D objects is introduced later in this chapter. Subobject editing is discussed in detail
in Chapter 11.
NOTE NOTE
It is good practice to set the
SOLIDHIST
system variable to
1
(Record) before starting
all 3D modeling work. This ensures that you will be able to edit your 3D solid models
if the need arises.
PROFESSIONAL TIP PROFESSIONAL TIP
If the
Show History
property is set to
Yes
to display the components of the composite
solid, as seen in Figure 8-3, the components will appear when the drawing is plotted.
Be sure to set the
Show History
property to
No
before you print or plot.
Selection Cycling Selection Cycling
When selecting objects that are on top of each other or occupy the same space,
selection cycling is the preferred method to select one of the objects. When editing,
you may need to erase, move, or copy one of the objects that overlap. Press the
[Ctrl]+[W]
key combination to turn on selection cycling. You can then select the object needed
from the
Selection
dialog box. When you need to cycle through objects at a pick point:
1. At the “select objects” prompt, press the
[Ctrl]+[W]
key combination. AutoCAD
displays the message
Selection Cycling
on. Pick to select the object you want.
2. When the
Selection
dialog box appears, select the desired object from the list.
3. Press the
[Enter]
key.
You can use the
SELECTIONCYCLING
system variable to turn on selection cycling
instead of using the
[Ctrl]+[W]
key combination. The
Selection Cycling
button on the
status bar is used for toggling selection cycling. The
Selection Cycling
button does not
appear on the status bar by default. Select the
Selection Cycling
option in the status bar
Customization
fl yout to add the
Selection Cycling
button to the status bar. There are
three settings for the
SELECTIONCYCLING
system variable:
• Off (0).
• On, but the list dialog box does not display (1).
• On and the list dialog box displays the selected objects that can be cycled
through (2).
It is recommended that you turn on selection cycling. With selection cycling turned
on, you can cycle and select the faces that may overlap one another.
In Figure 8-4, the two 3D objects occupy the same space. The tapered 3D object needs
to be moved up using the
3DMOVE
command. Turn on selection cycling. When you
select the tapered object, the
Selection
dialog box lists the objects overlapping at the pick
point. Select which object you want to work with by picking it in the dialog box. As your
cursor is over an object in the list, the object is highlighted in the drawing area.
SELECTIONCYCLING
Type
SELECTIONCYCLING
Toolbar
Status Bar
Selection Cycling