Autodesk 12812-051462-9011 User Guide 3 - Page 704

■ Exponential Sets exponential attenuation. Exponential attenuation is calculated between the start and end range values. You also specify the exponent to use. ■ Custom Falloff Specifies a custom curve to use for attenuation (falloff). Start Range The distance in world units where attenuation begins. Default=0.0. End Range Sets the distance in world units where the ray is fully attenuated. Default=100.0. This is not used by inverse square attenuation. Exponent Sets the exponent used in exponential falloff. Default=2.0. This is used only by exponential attenuation. Color These controls affect the behavior of light rays as they attenuate out. By default, as a ray fades out, it is rendered as the background color. You can set a custom color instead. Background As the ray attenuates out, returns the background (either the scene's background or the background specified locally in the Raytracer Parameters rollout) rather than the actual color of what the reflected/refracted ray sees. (Default.) Specify Sets the color that is returned by the ray as it attenuates out. If you choose not to use the background color, black or gray usually work best as the attenuation color, Custom Falloff group These controls are inactive unless the Falloff Type is set to Custom Falloff. Custom Falloff Uses the falloff curve to determine the falloff between the start and the end ranges. These are the controls for custom attenuation. The custom attenuation curve is at the left. The gray scale bar below the curve shows how the curve will affect the falloff as light rays diminish in strength. Near Sets the strength of the reflected/refracted ray at the start range distance. This is a normalized percentage that can range from 0.0 to 1.0. Default=1.0. Control 1 Controls the shape of the curve near the curve start. Default=0.667. Reflection and Refraction Maps | 5959