1. A three-dimensional image processing apparatus for creating an image of a trace having a width and formed on a ground surface or a water surface as a 3-D model having a width moves in contact with the ground surface or the water surface, the three-dimensional image processing apparatus comprising: position calculating means for calculating positions at opposite widthwise sides where the trace is to be created at specified time intervals, polygon generating means for generating polygons for the trace by successively determining the calculated positions at the opposite widthwise sides as vertices, polygon storage means for storing the generated polygons, texture storage means for storing textures to be adhered to the polygons, and texture adhering means for adhering the textures stored in the texture storage means to the polygons.