A free gem cut simulator for jewellery design students. Shape a stone's crown, pavilion and table and watch light travel through it. A well-cut gem sends light back to your eye as brilliance and fire. A poor cut lets it leak out of the back.
Side view · light path
Move your pointer or finger across the stone to follow a single ray.
Face up · what the eye sees
Cutter's notes
Cut report
What you can do with Gem Cut Light Simulator.
Watch rays enter, reflect and exit a cross-section of the stone.
Diamond, moissanite, sapphire, emerald and more, each with real refractive index and dispersion.
Adjust table, crown angle, pavilion angle and girdle.
Live scores for light return, fire, scintillation and leakage.
Timed rounds with hints to reach an Excellent cut grade.
See how the stone would sparkle from the top.
Get started in a few steps.
Practical benefits for students and designers.
Total internal reflection is hard to picture. Here you watch it happen.
Learn why a few degrees on the pavilion decide whether a diamond sparkles.
See how refractive index changes the ideal cut for each gem.
The challenge turns proportion theory into a skill you can test.
Made for learners and working designers.
The ideas behind the simulator, in brief.
Brilliance is the white light that returns to the viewer after reflecting inside the stone.
Fire is the flash of rainbow colours caused by dispersion, when white light splits into its spectrum.
Light hitting a facet at more than the critical angle reflects back inside. Diamond's critical angle is about 24.4°, which is why it can trap and return so much light.
If the pavilion is too shallow or too deep, light escapes through the back of the stone and it looks dark or glassy.
Study these topics in depth at IMS Design & Innovation Academy, Noida.
More free labs from DIA Design Labs.
It is an interactive model that shows how a gemstone's proportions change the way light travels through it, affecting brilliance, fire and leakage.
Diamond, moissanite and several coloured stones, each using its own refractive index and dispersion values.
It is a simplified 2D teaching model. Real grading also considers symmetry, polish and 3D facet arrangement.
Around 40.6° to 41° is widely considered ideal for a round brilliant diamond.
Yes. It is free and works on phones, tablets and desktops.
Gemmology, gem setting and jewellery CAD are part of the B.Sc. Jewellery Design programme at IMS DIA.
Study design at IMS Design & Innovation Academy. Explore the course, take the DIA Design Aptitude Test (D-DAT) or apply now.