18. A figure processing method comprising the steps of: a) approximating an object to be displayed by a polyhedron; b) sorting polyhedrons constituting the polyhedron into light-source polygons and non-light-source polygons; c) calculating a distribution and sum of optical energies in units of wavelengths from each light-source polygon to the non-light-source polygons; d) determining a display color of each non-light-source polygon from the sum of optical energies in units of wavelengths; and e) displaying the polygons on a display unit.
18. A figure processing method comprising the steps of: a) approximating an object to be displayed by a polyhedron; b) sorting polyhedrons constituting the polyhedron into light-source polygons and non-light-source polygons; c) calculating a distribution and sum of optical energies in units of wavelengths from each light-source polygon to the non-light-source polygons; d) determining a display color of each non-light-source polygon from the sum of optical energies in units of wavelengths; and e) displaying the polygons on a display unit. 20. The method according to claim 18, further comprising the steps of; g) checking whether each non-light-source polygon is displayed upon a projection calculation from a view point; h) checking whether each non-light-source polygon which is determined not to be displayed has an influence on optical energy distribution calculations of polygons to be displayed, and wherein the optical energy distribution calculation from each light-source polygon is performed only for non-light-source polygons to be displayed and non-light-source polygons which may have an influence on distribution calculations to of the non-light-source polygons to be displayed.