Media item relighting technique

The present invention concerns a method of method of relighting a media item comprising media elements. The method comprises, for at least some of the media elements: determining, in a first signal domain, a light transport function describing the appearance of a particular media element under different illumination conditions at least partly defined by positions of a light source used to illuminate the particular media element; sampling, in the first signal domain, the light transport function of the particular media element to obtain discrete data samples of the light transport function; projecting the data samples in the first signal domain into a sampling grid to obtain spatially sparsely and non-uniformly sampled light transport function; interpolating, in a second signal domain, the sparsely and non-uniformly sampled light transport function to obtain an approximate light transport matrix in the second signal domain; converting the approximate light transport matrix into the first signal domain to obtain an approximate substantially uniformly sampled light transport function in the first signal domain; and using, in the first signal domain, the approximate substantially uniformly light transport function to relight the media item.