1. A method of rendering a graphical scene using a computer, the method comprising: determining with the computer a plurality of functions that contribute to a light transport model of a scene; factoring with the computer the plurality of functions into a set of fixed functions and one varying function, the varying function being interactively determinable and therefore permitted to vary during the rendering, and the fixed functions being computed in advance of the rendering so as to be invariable during the rendering; determining with the computer a first radiance transfer vector that represents a product of the fixed functions in the wavelet domain; determining with the computer a second radiance transfer vector that represents the one varying function in the wavelet domain; determining with the computer an inner product of the first and second radiance transfer vectors to approximate a radiance of a point x in the scene; and rendering with the computer the scene.