A convex stone has no inward corners: a straight line between any two points inside it stays inside. Most cut stones are convex; a heart, with its notch, is not.
In more detail
A convex stone is the space on the inner side of every facet plane. That makes it fast to trace. A ray enters at the last plane it crosses and leaves at the first plane it meets.
How we measure it
Our light tools trace each convex cut as an intersection of half-spaces, one per facet. The census does not score the heart. A file of your own must be convex to within 0.1% of its size, or 0.2% for STEP.
Related terms
- Facet: A facet is one flat, polished face of a cut gemstone. Its angle and its direction around the stone decide where it sends light.
- Watertight: A watertight model is a closed surface with no holes, so it encloses a solid. In a closed mesh, exactly two triangles share every edge.
- Light census: The light census is our ray tracer behind the Cut Performance Wheel, the cut-page scores and the Cut Performance Index. It drops a fixed set of rays on a stone from above and counts where each one leaves.
- Measure your own stone: “Measure your own stone” lets three of our tools measure your own cutting file or 3D model. They use the same code and settings as for our cuts.