Ideal diffuse reflectors reflect light according to Lambert's cosine law, (these are sometimes called Lambertian reflectors). Lambert's law states that the reflected energy from a small surface area in a particular direction is proportional to the cosine of the angle between that direction and the surface normal. Lambert's law determines how much of the incoming light energy is reflected. Remember that the amount of energy that is reflected in any one direction is constant in this model. In other words, the reflected intensity is independent of the viewing direction. The intensity does, however, depend on the light source's orientation relative to the surface, and it is this property that is governed by Lambert's law.