The diffuse factor (Fd) expresses the general illumination of an object as a result of a specific light source. The virtual light rays strike the object and scatter in all directions. The amount of light scattered depends on the angle between the light source and the surface normal. The color of the object from this "diffuse" component (Cd) is given by

Cd = [Cn * Cl * Fd * cos(a)]/LDF
where Cn is the natural color of the object, Cl is the color of the light, Fd is the diffuse factor, cos(a) is the cosine of the angle between the light and the surface normal, and LDF is a "light distance factor" used to represent the general loss of radiant power as distance is increased from the light source.