1. A method for adding coloring information to a solid model of an object, the method comprising the steps of: acquiring a solid model for forming a surface shape of the object from a set of multiple planes; and estimating coloring information at the plane, wherein said estimating step comprises the steps of: regularly arranging multiple coloring points on the plane; and calculating coloring information of the coloring point as constants in a predetermined function based on photo-image data photographed of the object illuminated by a light source and photography information of the photo-image data, and storing the calculated constants as a two-dimensional array corresponding to an arrangement of the coloring point.