Some nice examples of computer drawn spirographs, and their generalization, Farris equations, can be found in this months Linux Gazette. The article also mentions the use of machines to inscribe guilloché, the regular geometric patterns seen on metal jewelry and watchcases. The machines that do this are shown at this RGM Watch Company site along with a page of examples from which I took the second illustration. Ah, so many careers, so few lives. I wonder if guilloché will soon be inscribed by computer driven machines with diamond tools. Optics have gone that way with glass lathes and the resulting decrease in price for reflecting telescope mirrors of significant aperture is quite astonishing.