The flux flow equation of Burkhard and Shealy is a simplified equation which can be used to evaluate the energy flux density at the image plane for a general optical system. Since the flux flow equation is based on the differential geometry of the wave front passing through the system, the energy flux density at the image plane can be computed by tracing a single ray through the system and using the flux flow equation. This technique has been used to calculate the meridional section of the point spread function of Wolter I x-ray telescopes and thin-film multilayered optics. Results, which have been obtained by the flux flow ray tracing method for the point spread function of several Wolter I x-ray telescopes and hybrid x-ray telescopes using convexed thin-film multilayered optics located near the primary focus, are compared with the rms blur circle results and the point spread function results obtained by conventional ray tracing techniques. © 1986 Optical Society of America.