The Bidirectional Reflectance Distribution Function (BRDF) describes the directional dependence of the reflected energy of a target as a function of illumination and viewing geometries. The BRDF also depends on wavelength and is determined by the structural and optical properties of the surface, such as shadow-casting, mutiple scattering, mutual shadowing, transmission, reflection, absorption, and emission by surface elements, facet orientation distribution, and facet density.
Relevance to remote sensing of the environment:
The BRDF is needed in remote sensing for the correction of view and illumination angle effects (for example in image standardization and mosaicking), for deriving albedo, for land cover classification, for cloud detection, for atmospheric correction and other applications. It gives the lower radiometric boundary condition for any radiative transfer problem in the atmosphere and is hence of relevance for climate modeling and energy budget investigations.