A method for setting processing parameters for fabricating an integrated circuit, by creating a mathematical model of a spin coated surface of a material over a non-flat substrate surface, where the mathematical model includes, a smoothing algorithm, where the smoothing algorithm uses as inputs only, a nominal thickness of the spin coated surface, a minimum thickness of the spin coated surface, and an interaction length, and a constraint that the spin coated surface cannot intersect the substrate surface, solving the mathematical model to determine the spin coated surface, and using the modeled spin coated surface to set the processing parameters for fabricating the integrated circuit.