Copyright Goodheart-Willcox Co., Inc. 456 AutoCAD and Its Applications—Advanced The Image property is used to add a transparency map to the material. White areas in the image or texture are transparent. Black areas are opaque. All other colors produce varying degrees of transparency based on their grayscale values. The Amount property is applied to the transparency map. Maps are discussed later in this chapter. The Image Fade property determines how much of an impact the transparency map has on the transparency of the material. A setting of 100 means the transparency is completely see-through based on the transparency map. As the setting is decreased, a higher percentage of transparency is determined by the Amount property. Translucency is a quality of transparent and semitransparent materials that causes light to be diffused (scattered) as it passes through the material. See Figure 17-15. This makes any object with the material applied to it appear as if it is being illuminated from within, or glowing. The thicker the material, the more pronounced the effect. When the Translucency property setting is 0, light appears to travel through the material, lighting the opposite side. A setting of 100 creates a material similar in appearance to frosted glass. Refraction, sometimes specifi ed as the index of refraction (IOR), is a measure of how much light is bent (refracted) as it passes through transparent or semitransparent materials. Refraction is what causes objects to appear distorted when viewed through a bottle or glass of water. See Figure 17-16. The Refraction property sets the IOR. The higher the value, the more that light is bent as it passes through the material. The IOR of water is 1.3333. You can enter a value in the text box or select a preset IOR by picking the name that is displayed to the left of the text box. Cutouts Category The Cutouts property allows you to select an image or texture to use for a pattern of cutouts (holes), Figure 17-17. Black areas in the image will appear to be see-through, as if there is no object in those areas. White areas in the image have the normal mate- rial colors. This is similar to using a transparency map, but without the other transpar- ency settings. Figure 17-18 shows an example of a cutout map applied to a material. Self Illumination Category Self illumination is an effect of a material producing illumination. See Figure 17-19. For example, the surface of a neon tube glows. However, in AutoCAD, a material with self illumination will not actually add illumination to a scene. This effect can be simulated with properly placed light sources. Luminance is defi ned as the value of light refl ected off a surface. The Self Illumination category contains several properties related to self illumination and luminance, Figure 17-20. A B Figure 17-15. The effect of translucency. A—The glass material has a translucency setting of zero. B—When the translucency setting is increased, light is diffused within the material. Notice how the glass appears slightly frosted. A full-color image is provided on the companion website. www.g-wlearning.com/CAD/