Copyright Goodheart-Willcox Co., Inc. 500 AutoCAD and Its Applications—Advanced PROFESSIONAL TIP PROFESSIONAL TIP If there are no lights in the scene or all lights are turned off, default lighting is acti- vated so that you can still see what you are doing. If you render a scene and the image appears black, lights in the scene may have their intensity set too low or they may be positioned too far away from the objects in the scene. Shadows Shadows Shadows are critical to the realism of a rendered 3D model. A model without shadows appears obviously fake. On the other hand, a model with realistic mate- rials and shadows may be hard to recognize as computer generated. In AutoCAD, all lights, including default lights, cast shadows. You may not see shadows in the view- port depending on the current visual style settings, but shadows are always calculated in the rendered image. As previously discussed, the Shadow option that appears in command prompts when creating lights is only available for backward compatibility with older releases of AutoCAD. All lights display realistic shadows with soft edges. Adding a Background Adding a Background A background is the backdrop for your 3D model. The background can be a solid color, a gradient of colors, an image fi le, the sun and sky, or the current AutoCAD drawing background color. By default, the background is the drawing background. One way to change the background for your drawing is to use the BACKGROUND command. This command opens the Background dialog box, Figure 18-20. The Type: drop-down list is used to specify the type of background. The options are None, Solid, Gradient, Image, and Sun & Sky. When the None option is selected, the current AutoCAD viewport color is used. The other background options are discussed in the following sections. You can also set the drawing background when creating a named view using the New View/Shot Properties dialog box. Creating named views is introduced in Chapter 3. A background for a named view is specifi ed using the drop-down list in the Background area of the View Properties tab in the New View/Shot Properties dialog box. The background options correspond to those in the Background dialog box. BACKGROUND Type BACKGROUND Pick to select a color Solid is selected Figure 18-20. The Background dialog box with the Solid option selected.