1. An image processing apparatus, for using computer graphics to generate a polygon model in a three-dimensional coordinate space, comprising: geometry means for employing data for a first model read from a storage medium to generate a second model by the magnification of said first model at a predetermined ratio, for reversing the directions of the normal vectors of polygons of said second model, and for enclosing said first model in said second model; and rendering means for performing rendering for said first and said second models processed by said geometry means.