Gemcad Files of Famous Diamonds

by Robert W. Strickland

GemCad for Windows, created by Robert Strickland, is a computer-aided design (CAD) program for the design of gemstone cutting patterns. 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. The program has three main purposes:

(1.) Proof-cutting an existing diagram. Proof-cutting a design on the computer allows you to check the accuracy of the diagram and discover pitfalls before wasting valuable rough.

(2.) Editing a diagram. You can take an existing diagram and modify it to optimize its optical performance for different materials. You can scale a diagram to make it fatter or skinnier to fit a certain piece of rough.

(3.) Designing a stone from scratch. Advanced users can use GemCad to create new designs.
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. The program has three main purposes:

1. Proof-cutting an existing diagram. Proof-cutting a design on the computer allows you to check the accuracy of the diagram and discover pitfalls before wasting valuable rough.
2. Editing a diagram. You can take an existing diagram and modify it to optimize its optical performance for different materials. You can scale a diagram to make it fatter or skinnier to fit a certain piece of rough.
3. Designing a stone from scratch. Advanced users can use GemCad to create new designs. GemCad frees the user from the tedious calculations required to determine angles.

GemCad doesn't model curved surfaces or notches but is limited to convex designs that can be cut on any faceting machine.

Here is a screen shot (reduced in size). You can see the path of a light ray through the stone. GemCad's screen is divided into four windows or “views.” The Four View shows the stone from four different viewpoints. The Spin View shows a 3-D view of the stone that can be tilted and rotated. The Cutting Instructions are shown in a table at the bottom. The New Facet Info Box collects information for cutting a new tier of facets