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