A method of predicting scattering of an electromagnetic (EM) wave incident on a surface with location-dependent scattering properties such as an engineered electromagnetic surface is based on generalized Snell's Law and includes offsetting a direction of scattering by a vector determined based on the properties of the surface at a particular point of incidence. The method solves the problem of “exact path calculation,” by exhaustive search of possible locations for points of incidence, followed by a fine approach, both steps using the data describing the local properties of the surface.