The specification of the transfer function for luminous flux in an enclosure is a necessary component of the lighting design process. Daylight and lamplight excitations are coupled to the luminance and illuminance distributions in space by the luminous refiectances of the surfaces and the geometrical parameters. An idealized representation of this luminous transfer utilizes a postulate of uniform excitation and response over discrete spatial regions. This leads to a matrix equation and an equivalent circuit or network representation of the light distributions. The discrete formulation is particularly adapted to numerical specification of the transfer function for luminous flux and thus to the lighting design process.
Philip F. O’Brien, "Luminous Transfer in Discrete Spaces," Appl. Opt. 6, 1469-1472 (1967)