3D Graphics Programming with QuickDraw 3D 1.5.4

Point Lights

A point light is a light source that emits rays of light in all directions from a specific location. The illumination that a point light contributes to a surface depends on the basic properties of the light source (its intensity and color) together with the orientation of the surface and its distance from the light source.

A point light can suffer attenuation, in which case objects closer to the light source receive more illumination than objects farther away. QuickDraw 3D allows you to specify one of several attenuation values that determine the precise amount by which the intensity of a point light decays over distance. For example, you can use the constant kQ3AttenuationTypeInverseDistance to have the intensity of a point light be inversely proportional to the distance between the illuminated surface and the light source. See "Light Attenuation Values" for a complete list of the available attenuation values.