This spreadsheet provides a systematic template for solving radiative exchange problems involving up to 20 diffuse-gray surfaces. Spaces are set up for surface radiative properties (area, emissivity (ε)) and for view factors connecting all pairs of surfaces. Surface and spatial radiative resistances are computed from the input, the coefficients of the equations for Radiosity are compiled and the equations solved. A six-surface example is provided, and the spreadsheet automatically sets up and solves the required equations for as many as 20 diffuse-gray surfaces. Complete derivations of the Radiosity method for black and gray surfaces are provided and a schematic of the equivalent dc circuit is generated.

Note that we engineers use the radiosity method for the radiative transport of heat.   In computer graphics the same method is used on a massive scale for the transport of visible light accounting for its red, green, and blue components separately.