Lambertian Reflectance

See Also: Lambert's cosine law

If a surface exhibits Lambertian reflectance, light falling on it is scattered such that the apparent brightness of the surface to an observer is the same regardless of the observer's angle of view. More technically, the surface Luminance is the same regardless of angle of view. For example, unfinished wood exhibits roughly Lambertian reflectance, but wood finished with a glossy coat of Polyurethane does not (depending on the viewing angle, Specular Highlight s may appear at different locations on the surface). Not all rough surfaces are perfect Lambertian reflectors, but this is often a good approximation when the characteristics of the surface are unknown.

In Computer Graphics , Lambertian reflection is often used as a model for Diffuse Reflection , and is calculated by taking the Dot Product of the surface's normalized Normal Vector

\mathbf{N}

and a normalized vector

\mathbf{L}

pointing from the surface to the light source. This number is then multiplied by the color of the surface and the intensity of the light hitting the surface:

C---I_{L},

where

I_{D}

is the intensity of the diffusely reflected light (surface brightness),

C

is the color and

I_{L}

is the intensity of the incoming light. Because

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Lambertian Reflectance