1. An image synthesis method comprising: a synthesis procedure for synthesizing an image of an object in a pose at a location under an illumination condition using appearance data of said object; said appearance data comprising: a three-dimensional shape of said object; and a texture space, which is an image space, defined by a texture group indicating luminance and/or color information of each position of a surface of said object under various illumination conditions; said synthesis procedure comprising the steps of: generating an illumination fluctuation space, which is an image space, defined by an image group under various illumination conditions in said pose at said location from said three-dimensional shape and said texture space, said generating using coordinate transformation of the texture space; and collating an image from said illumination fluctuation space by linear combination of a plurality of textures.