A method for solving the three-dimensional equation of transfer for an inhomogeneous static medium is described. The resolution of the three-dimensional transfer equation is important for studying the planetary atmosphere where an accurate model of the radiation field near the terminator region and in the nightside is necessary. The procedure involves: the reduction of the three-dimensional equation to a one-dimensional equation system; the resolution of this system by the discrete ordinate method, and reconstruction of the three-dimensional radiation field. This method considers variations in atmospheric parameters and reflectance at the bottom of the atmosphere relative to spatial and frequency parameters. 22 refs.