bi-hemispherical reflectance

Bi-hemispherical reflectance is the reflectance of a surface under diffuse illumination (with no direct component). Bi-hemispherical reflectance is an important part of the Bidirectional reflectance distribution function over all viewing and illumination directions of a hemisphere.{{cite book|last=Nicodemus|first=F.E. |author2=J.C. Richmond |author3=J.J. Hsia|title=Geometrical Considerations and Nomenclature for Reflectance|publisher=National Bureau of Standards|date=October 1977|url=http://graphics.stanford.edu/courses/cs448-05-winter/papers/nicodemus-brdf-nist.pdf|accessdate=8 April 2013|bibcode=1977nbs..reptR....N }} It is sometimes called "white-sky albedo".