I have been wondering how to create a diffraction grating material with cycles.
From the Wikipedia article:
In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element.
Diffraction is what creates the colors on a compact disc. I am interested mainly in reflective rather than transmissive diffraction, i.e. the light is diffracted on a bounce rather than as it passes through a material. I have heard that cycles currently does not support true diffraction (though most of what I have read is from a while ago). So I would be equally interested in some kind of node trick to achieve the effect if this is still not so.