Copyright Goodheart-Willcox Co., Inc. Chapter 4 Understanding Three-Dimensional Coordinates and User Coordinate Systems 87 First, draw a three-unit diameter sphere with its center at 7,5. Display the drawing from the southeast isometric preset. To help see how the UCS is changing, make sure the UCS icon is displayed at the origin of the current UCS. The UCS icon drop-down list is found in the Coordinates panel of the Home and Visualize tabs of the ribbon and provides access to three options of the UCSICON command. See Figure 4-10. Pick the Show UCS Icon at Origin button to ensure the icon is displayed at the origin. This option can also be selected from the UCS icon shortcut menu. Also, set the X-ray visual style current, and set the opacity to 25%. In the Visual Styles panel of the Visualize tab, use the Opacity slider to adjust the value. You can also type a numerical value to the right of the slider. Now, the sphere is drawn and the UCS icon is displayed at the origin of the current UCS (or at the lower-left corner of the screen, depending on the zoom level). However, the WCS is still the current user coordinate system. You are ready to start changing the UCS to meet your needs. Pick the UCS icon and move the pointer over the origin grip. Select Move Origin Only. Now move the UCS origin to the center of the sphere using the center object snap. Notice that the UCS icon is now displayed at the center of the sphere, and its orienta- tion has remained the same, Figure 4-11. Also, if the grid is displayed, the red X and green Y axes of the grid intersect at the center of the sphere. Study Figure 4-12 and continue as follows. Keep in mind that the point you are locating—the center of the cone on the sphere’s surface—is 30° from the X axis and 30° from the XY plane. For ease of visualization, zoom in so the sphere fi lls the screen. Right-click on the UCS icon to display the UCS icon shortcut menu. Then, select Rotate AxisZ. Enter 30 for the rotation angle or select it dynamically. Watch the posi- tion of the UCS icon change when you press [Enter]. See Figure 4-12B. UCS Ribbon Home Coordinates Visualize Coordinates Origin Type UCS UCS Ribbon Home Coordinates Visualize Coordinates Z Type UCS Pick Figure 4-10. The UCS icon drop- down list provides access to the Origin, Off, and On options of the UCSICON command. Figure 4-11. The UCS origin is moved to the center of the sphere.