Copyright Goodheart-Willcox Co., Inc. 90 AutoCAD and Its Applications—Advanced PROFESSIONAL TIP PROFESSIONAL TIP It is recommended that you have the UCS icon turned on at all times when working in 3D drawings. It provides a quick indication of the current UCS. Changing the Coordinate System To construct a three-dimensional object, you must draw shapes at many different angles. Different planes are needed to draw features on angled surfaces. To construct these features, it is easiest to rotate the UCS to match any surface on an object. The following example illustrates this process. The object in Figure 4-15 has a cylinder on the angled surface. The EXTRUDE command, which is discussed in Chapter 6, is used to create the base of the object. The cylinder is then drawn on the angled feature. In Chapter 13, you will learn how to dimension the object as shown in Figure 4-15. UCS icon options UCS options Figure 4-14. Setting UCS and UCS icon options in the UCS dialog box. Figure 4-15. This object can be constructed by changing the orientation of the coordinate system.