GemDiagram Docs

Presets

Presets are finished designs you can load and use as a starting point. GemDiagram ships with a few well-known cuts; you can load them, edit them, and save your variants.

Loading a preset

Click the Presets dropdown in the top bar (or when you click New Design and pick Manual Mode, it opens blank). The list shows:

  • Round Brilliant: 57 facets, 4-fold symmetry, the most common diamond cut.
  • Step Cut Octagon: 25 facets, 8-fold symmetry with step facets instead of brilliant facets.
  • Portuguese Round: 69 facets, 32-fold/16-fold pavilion, more facets for extra sparkle.

Pick one, and the design loads. You can now:

  • Edit it: Adjust any tier's angle, distance, or indices.
  • Change the material: Swap to a different gem from the Material dropdown.
  • Save it: Click Save to keep your edits as a new .facet file.

Why start with a preset?

Building a cut from scratch is hard — you need to know typical angles, how many facets to use, symmetry patterns, and the geometry. A preset gives you a known-good starting point:

  • The Round Brilliant pavilion angles are optimized for Diamond to avoid windowing.
  • The Step Cut proportions are tuned to the 8-fold grid and the table size.
  • The Portuguese Round uses denser faceting for maximum light return.

Tweak any of these, and you have a personal variant tailored to your stone or design taste.

Importing your own designs

You can also load a .facet file you've saved before, or import a .asc, .gem, or .gcs file from another tool. See Import an Existing Design.

Making a preset-derived design

A common workflow:

  1. Load the Round Brilliant preset.
  2. Change the Material from Corundum (the default) to your stone (say, Moissanite).
  3. Check the Critical angle stat tile — if the pavilion mains angle is now too shallow, increase it slightly.
  4. Adjust the Crown scale slider to make the crown shallower or deeper.
  5. Save as my-moissanite-round.facet.

You now have a Round Brilliant tuned to Moissanite's higher refractive index, without reworking every tier by hand.

Sharing presets

Presets are just .facet files — save a design and share it with another GemDiagram user. They can load it and edit from there. There's no "preset library" yet, but your saved files are your personal library.