Computer-implemented methods of simulating backlights, and machine-readable media for carrying out such methods, are disclosed. The backlight may include a plurality of components, each component having at least one element. Some methods can include: tracing rays to an output plane of the backlight; collecting information from the traced rays to produce a first database containing spatial and directional information of the rays incident on the output plane; associating a probability function with the output plane; and calculating a second database containing spatial and directional information for rays exiting the output plane as a function of the probability function and the database. The output plane can if desired correspond to a stack of optical films, e.g., diffusing films, prismatic films, reflective polarizing films, turning films, and the like. Preferably, the probability function is a bi-directional scattering distribution function (BSDF) of the output plane.