This spreadsheet provides a systematic template for solving radiative exchange problems involving up to 20 diffuse-gray surfaces.  The worksheet sets up spaces for surface radiative properties (area, emissivity (ε)) and for view factors connecting all pairs of surfaces. The algorithm computes  Surface and spatial radiative resistances from the input.  It compiles coefficients of the equations for Radiosity solves the equations. A six-surface example is provided.  This 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 within.  As seen below in the example, this worksheet generates a schematic of the equivalent dc circuit.

Note that we engineers use the radiosity method for the radiative transport of heat.   Practitioners in  computer graphics use this same method on a massive scale for the transport of visible light.  Such rendering accounts for red, green, and blue components separately.