LUMINANCE
Definition
A <LUMINANCE> is a <Property> that is the intensity of light emitted at a point on a <SURFACE> and in a given direction, calculates as L_v = dI_v/dA where dI_v is the luminous intensity of an element of A <SURFACE> with A <AREA> dA of the orthogonal projection of this element on a plane perpendicular to the given direction