The 3D Gemstone Simulator is a free Digital Gemology tool that renders a cut stone as a camera sees it. You choose the cut, gemstone, carat weight, color, clarity, cut grade and lighting.
In more detail
It is for seeing, not scoring. The only figures it reports are the Light Return shares, the cut grade proportions and the size. Its report is a simulation of the geometry, not a grading report.
How we measure it
The graphics card ray-traces each pixel with full Fresnel reflection, three-color dispersion and body color. Each path takes up to 14 bounces, and a still image refines over up to 64 samples per pixel. In doubly refractive stones it traces both rays, so moissanite's facet edges double. It has ten lighting scenes.
Related terms
- Light Return: Light Return sorts each point of a face-up stone by the direction its light came from. Its four classes, direct, indirect, contrast and leakage, together cover the whole face-up stone.
- Light map: A light map is a face-up picture of a cut stone, colored by the direction each point's light came from. Red is direct light, green is indirect light, blue is contrast, and a dark color is leakage.
- Ray tracing: Ray tracing follows straight lines of light through a model of a stone. At each facet it applies refraction and reflection, and it records where the light comes from or where it leaves.
- Fresnel reflection: Fresnel reflection is the share of light that a surface reflects instead of letting through. The Fresnel equations give that share from the two refractive indices, the angle and the polarization.
- Doubly refractive: A doubly refractive stone splits light into two rays that vibrate at right angles and travel at different speeds. Each ray has its own refractive index.
- Simulator cut grade: The simulator cut grade shows how a worse make of the same design looks. Each grade moves the crown angle, pavilion angle, girdle, table and culet by a fixed step.