Lambertian reflectance

Lambertian reflectance is named after Johann Heinrich Lambert, who introduced the concept of perfect diffusion in his 1760 book Photometria.

[2] Spectralon is a material which is designed to exhibit an almost perfect Lambertian reflectance.

This technique causes all closed polygons (such as a triangle within a 3D mesh) to reflect light equally in all directions when rendered.

The reflection decreases when the surface is tilted away from being perpendicular to the light source, however, because the area is illuminated by a smaller fraction of the incident radiation.

[3] The reflection is calculated by taking the dot product of the surface's unit normal vector,

For example, in ultrasound imaging, "rough" tissues are said to exhibit Lambertian reflectance.

Diagram of Lambertian diffuse reflection. The black arrow shows incident radiance , and the red arrows show the reflected radiant intensity in each direction. When viewed from various angles, the reflected radiant intensity and the apparent area of the surface both vary with the cosine of the viewing angle, so the reflected radiance (intensity per unit area) is the same from all viewing angles.