BRDF bidirectional reflectance distribution

Figure 3.14 The bidirectional reflectance distribution function (BRDF) specifies how much of the incident light coming from direction (6l,

Sometimes it is important to consider the direction of reflected irradiation exitent from a surface. A property called the bidirectional reflectance distribution function (BRDF) is used to specify the directional distribution of the reflected intensity for a specified direction of incident radiation [2-4]. A specular surface is a mirrorlike surface for which the incidence angle is equal to the reflection angle. For a diffusely reflecting surface, the reflected intensity is the same in all directions, and if perfectly reflective, the BRDF is l/n sr. ... 

Bidirectional reflectance distribution function (BRDF) n. The ratio of radiance per unit irradiance, used for describing the... 

The reflectance properties of a surface are characterized by its bidirectional reflectance distribution function (BRDF). The BRDF is the ratio of the scene radiance in the direction of the observer to the irradiance due to a Hght source from a given direction. It captures how bright a surface will appear when viewed from a given direction and illuminated by another. For example, for a flat Lambertian surface illuminated by a distant point light source, the BRDF is constant hence, the surface appears equally bright from all directions. For a flat specular (mirrorHke) surface, the BRDF is an impulse function as determined by the laws of reflection. 

This chapter explains how to characterize the angular distribution of optical scatter from an opaque surface. In particular it focuses on measurement of the bidirectional reflectance distribution function (BRDF). BRDF is a convenient and well-accepted means of expressing optical scatter levels for many purposes (1, 2). 

Bartell, F. O., Dereniak, E. L., and Wolfe, W. L. (1980). The theory and measurement of bidirectional reflectance distribution function (BRDF) and bidirectional transmittance distribution function (BTDF). In Radiation Scattering in Optical Systems, Vol. 257, p. 154. SPIE. 

To characterize reflection that is not perfectly specular, we use the bidirectional reflectance distribution function (BRDF). This function converts irradiance on a surface to the reflected radiance L from that surface ... 

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