If a surface exhibits Lambertian reflectance, light falling on it is scattered such that the amount of light an observer sees, the surface luminance, is the same regardless of their angle of view. Not all rough surfaces are perfect Lambertian reflectors, but this is often a good approximation when the characteristics of the surface are unknown. The word luminance, a synonym for luminosity, means emitting or reflecting light. ...

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 and a normalized vector 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: Computer graphics (CG) is the field of visual computing, where one utilizes computers both to generate visual images synthetically and to integrate or alter visual and spatial information sampled from the real world. ... Diagram of diffuse reflection Diffuse reflection is the reflection of light from an uneven or granular surface such that an incident ray is seemingly reflected at a number of angles. ... In mathematics, the dot product, also known as the scalar product, is a binary operation which takes two vectors and returns a scalar quantity. ... A normal vector is a vector which is perpendicular to a surface or manifold. ...

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

,

where α is the angle between the direction of the two vectors, the intensity will be the highest if the normal vector points in the same direction as the light vector (cos(0) = 1, the surface will be perpendicular to the direction of the light), and the lowest if the normal vector is perpendicular to the light vector (cos(π) = 0, the surface runs parallel with the direction of the light).

Lambertian reflection is typically accompanied by specular reflection, where the surface luminance is highest when the observer's angle is the same as the angle of the light source. This is simulated in computer graphics with Phong shading. Diagram of specular reflection Specular reflection is the perfect, mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected onto a single outgoing direction. ... See also Phong reflection model The term Phong shading is used indiscriminately to describe both an illumination model and an interpolation method in 3D computer graphics. ...

See also

• Lambert's cosine law
• Specular reflection
• Diffuse reflection