Diffraction Shading Models for Iridescent Surfaces

Diffraction and interference are optical phenomena which split light into its component wavelengths, hence producing a full spectrum of iridescent colors. This paper develops comput er graphics models for iridescent colors produced by diffractive media. Diffraction gratings, certain animal skins and the crystal structure of some precious stones are known to produce diffraction. Several techniques can be employed to derive solutions to the diffraction problem including: (1)Electromagnetic boundary value methods (2)Applying the Huygens-Fresnel principle (3)Applying the Kirchoff-Fresnel theorem (4)Fourier optics. Previous work in developing diffraction models for computer graphics has used boundary value methods and Fourier optics but no models using HuygensFresnel principle have been published. This paper derives a set of diffraction solutions based on the Huygens -Fresnel principle, which are then used to extend well-known illumination models and are incorporated into a ray tracer.