Getting started

Instructions for running the program:
Download the .jar file.
Make sure you have Java installed and up-to-date.
Locate the downloaded file and simply double-click it to run it. It requires no installation and runs from just this file. It should work fine on any operating system, but I've only tested it on Windows so far, so tell me if you have any problems with opening it.

About files: The program should be able to read most .gem files from GemCAD, but they may behave unexpectedly if they have preforms. It should also be able to load .asc files from FacetDiagrams.org. The program can save and load files in the .lap format that I designed.

Another thing that might be relevant: If your screen resolution is below 1600 x 900, the program may not display properly. If this is a problem, tell me and I can try to figure something out, most likely making the rendering view smaller.

Here's a little tutorial for getting started:

Standard Round Brilliant
(at least with one set of angles I saw for quartz, feel free to use whatever material and angles you want)

If you need to change the index gear to something other than 96, go to "Edit" in the top menu bar, and click "Set index gear..." This will open a menu where you can change the index gear (and which way it rotates (cw/ccw) and how it is oriented, if you want).

If you need to change the refractive index to something other than the value for quartz, go to the "Optics" tab in the upper-left menu. At the bottom of the menu there is a dropdown menu of minerals where you can select which mineral you are using, and it will set the refractive index and dispersion and show you the critical angle. I don't have every mineral there, so you can also set the refractive index manually by entering a number in the box next to "Refractive index," or using the slider to pick a number, and then clicking "Set refractive index."

Now click on the "Cut facets" tab. In the setting for "Rotation symmetry" near the bottom, enter 8, and check the "Y" box under "Reflection symmetry." This will make the cuts have 8-fold mirror-image symmetry. (I should probably make the reflection symmetry less confusing)

To create the girdle outline, enter 90 for the angle and 3 for the index. Clicking somewhere else should set the height so that the cuts will be within the initial cube of rough. It only does this if the initial cut is at 90 degrees, for basic regular polygon shapes (triangles, squares, etc, depending on the symmetry). You should also see a preview of the planes which will be cut. Click the "Cut facets" button at the bottom of the menu, and your design should be a 16-sided barrel for the girdle outline of a round brilliant.

In the rendered view of the design on the right, you can click and drag to rotate the view. You can also right-click to see the paths of light rays (press escape to delete them if there are too many). When viewing the design from the above you can see where different indices will cut. Find the top face and click it to select it. Then click the "Selection" tab on the left, and click the button "Use midpoint to cut." This adds a meetpoint at the center of the face, giving a convenient culet point.

Back in the "Cut facets" tab, enter an angle of 45 (degrees), index of 3, and leave the height blank, as it will be determined by the meetpoint. If you click anywhere in the program, it should calculate the planes which will be cut and display previews of them in the graphical view on the right. Then click "Cut facets." You should end up with a set of pavilion break facets meeting at a culet point.

Next, enter an angle of 43 degrees and index of 0 (or 96, same thing). For the meetpoint, go to the graphical view, find the point where the pavilion break facets meet the girdle facets at the index of 96 and click it (you can check that it's at the right index by looking at the design from the top). In the "Selection" tab, click the "Use point to cut" button. This sets the point as a meetpoint. At this point, you should see the preview planes. If the meetpoint was at a different index than the index entered, they will look off (because they will cut away the whole pavilion). The easiest way to fix this is to change the index of the cut to match the meetpoint you selected. Aftering pressing the "Cut facets" button, you should have the pavilion complete.

In the top menu bar, click "Edit," then "Transfer." This will transfer the design so that you can move on to the crown.

Select a point on a girdle edge at index 96 or 3 and use that point as a meetpoint to cut the girdle to the thickness you want. You can zoom in/out by scrolling in/out. You can also select a point at a specific fraction of an edge in the "Selection" menu. Cut at an angle of 47 degrees and index 3 to get the crown break facets.

Next, cut at angle 42 and index 0 or 96, using the meetpoint of the girdle facets and crown break facets at index 96. This should give the crown main facets.

Next, cut at angle 27 and index 6, using the meetpoint of the crown break and crown main facets at index 6. This should give the star facets.

Lastly, cut at angle 0, using a meetpoint of the crown main and star facets, to form the table.

This completes the design. You can try right-clicking in the graphical view from above to see the paths of light rays, which should bounce off the pavilion facets and back out the crown. If you set the dispersion, you can also see how different colors of light trace out different paths.

If you want, you can save this model by clicking "File" in the top menu bar, and then "Save as..." This will open a file saving dialogue where you can choose where to save it and what file name to use. The file extension will be ".lap." You can later load the file with the "Load" option under "File" in the top menu bar.

There should also be an option under "File" which will show you a faceting diagram generated for the model, including a list of cuts with angles and indices, and relevant information about dimensions, symmetry, refractive index, etc. If it works correctly, anyway. It may take a while to load, and may display incorrectly on very complicated designs.

The "Info" tab will also show you information about number of facets, dimensions, yield from rough, etc, and also includes something to show what the gem looks like after each cut is made.

The "Transform" tab contains tools for centering, translating, rotating, reflecting, and scaling the model. Scaling can be used to create oval shapes from round shapes, for example. (This may not always work, and sometimes can lead to non-planar facets, which will cause all sorts of other problems, so be careful using it.)

There are also some other useful features, like tangent ratio scaling. Select a facet, then go to "Tangent ratio scaling..." in the "Tools" part of the top menu bar. You can then enter a new angle, and it will scale the whole crown and pavilion so that that facet is at the angle you entered, and the meetpoints are preserved. This allows you to easily edit models to work for different refractive index materials.