Copyright Goodheart-Willcox Co., Inc. 98 AutoCAD and Its Applications—Advanced Dynamically moving and aligning the UCS to an object surface can also be achieved by using the Object option of the UCS command. This option is also avail- able in the UCS icon shortcut menu and is discussed later in this chapter. Rotating the UCS on an Axis The axis grips of the UCS icon enable you to rotate the icon in any direction, and to cycle between rotation options. For example, pick the UCS icon to display the grips, and then move the pointer over the Z axis grip (but do not select it). See Figure 4-24A. The fi rst item in the Z grip menu is Z Axis Direction. Picking this option is the same as picking the Z axis grip. Select this option and notice that it enables you to select the direction of the Z axis. Use object snaps to assist, or turn ortho on to limit selections to 90°. In addition, if dynamic input is on, you can press the [Ctrl] key to cycle through the three options in the grip menu. See Figure 4-24B. The other two options in the grip menu allow the Z axis to be moved in relation to one of the other two axes. Test each of these options to see how they function. The Rotate Around X Axis option limits rotation of the Z axis to around the X axis, and the Rotate Around Y Axis option limits rotation to around the Y axis. Current UCS A B C UCS moved to outer surface Figure 4-23. Using the UCS icon to move the UCS to a curved surface. In this example, the UCS icon origin grip is used to access the Move and Align option. A—The current UCS is located at the center point of the left curve of the model. This is apparent in the top view. B—A top view of the model. C—A new UCS is established on the outer surface by moving the UCS icon to the surface and picking. Note that the Z axis is normal to the surface.