The lighting and daylighting designs of a room often include a prediction of the average illu minance on the working plane, and the illuminance or luminance distribution on various surfaces. It is very difficult to obtain an analytical solution of various interior inter-reflection problems which is based on the Fredholm type integral equation.
In this paper, the authors have accomplished a program of FORTRAN IV for the numerical solution based on the photometric quantities by using the point-by-point method, the luminous flux transfer method and the superposition theorem in an idealized room. It is possible to predict the direct and total flux received by a rectangular surface, and the average illuminance, and the illuminance distribution by using this program, and moreover to predict an isolux diagram on the horizontal or vertical plane from the output of the digital computer such as the line printer or X-Y plotter.