GemCad for Windows is a computer-aided design (CAD) program for faceted gemstones. It runs under Windows 95 or later on PC compatibles with screen resolution of at least 800 x 600. GemCad simulates a faceting machine and shows you accurate 3-D views of the stone. GemCad understands symmetry, so you typically have to “cut” only a fraction of the facets to get the full design. GemCad can follow paths of light rays through the stone to allow you to optimize a design to minimize light loss. The end product is an accurate faceting diagram that shows several views of the stone with accurate angles, indexes and dimensions.