The limits of ray optical methods to provide a valid model for describing the propagation of electromagnetic radiation are explored. We briefly review fundamentals of ray optics as well as
various extensions. This review is partially intended to emphasize that existing ray based methods are able to address most, if not all, wave phenomena. In addition, we propose an
extension of ray optics which interprets rays as generalized trajectories in an abstract configuration state. This allows us to propose the use of rays and ray optics as fundamental and practical concept to compute any wave phenomenon, including rigorous diffraction problems. Wave optics, in this context, becomes a convenient and efficient method to calculate the ray transfer properties. In addition, our concept facilitates
interfacing conventional ray-tracing methods with wave optical methods to predict diffraction.