Abstract: A method of transforming an input video image data onto a three-dimensional surface is disclosed which comprises the steps of defining the three-dimensional surface, providing mapping data for transforming the input video image data onto the surface, storing the input video image data in a first memory, transforming the input video image data stored in the first memory according to the mapping data so as to provide an output video image data, calculating first vectors representing, respectively, orientations taken by minute areas on the surface, calculating second vectors representing, respectively, directions from the minute areas toward a virtual light source disposed in a position, calculating weighting factors according to the first and second vectors, the weighting factors quantifying shading to be caused on the minutes areas by the virtual light source, and weighting the input video image data or the output video image data according to the weighting factors.