---
title: "Ray tracing: meaning in gemology"
description: "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…"
url: https://digitalgemology.com/learn/glossary/ray-tracing
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · How we measure

# Ray tracing

Also called ray trace

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.

## In more detail

Ray tracing describes the geometry of a cut and the optics of its material. Each tracer leaves out some physics for speed, so results from different tracers differ.

## How we measure it

Our tools trace light in four ways. The simulator traces per pixel, with up to 64 samples and 14 bounces. The Brightness & Tilt Analysis uses a 132 × 132 grid and 12 bounces. The Cut Grading Tool's brilliance uses an 84 × 84 grid and 12 bounces. The light census uses 3,200 seeded rays and 12 bounces. All four treat total internal reflection as lossless.

## Related terms

- [Light census](https://digitalgemology.com/learn/glossary/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.
- [Snell's law](https://digitalgemology.com/learn/glossary/snells-law): Snell's law sets the direction of refracted light: n₁ sin θ₁ = n₂ sin θ₂. The angles are measured from the normal to the surface.
- [Fresnel reflection](https://digitalgemology.com/learn/glossary/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.
- [Total internal reflection](https://digitalgemology.com/learn/glossary/total-internal-reflection): Total internal reflection happens when light inside a stone meets a facet beyond the critical angle. The facet then acts as a perfect mirror, and all the light reflects back into the stone.
- [3D Gemstone Simulator](https://digitalgemology.com/learn/glossary/3d-gemstone-simulator): 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.

## Learn more

- [Four light measures, side by side](https://digitalgemology.com/about/how-we-measure/light-measures)
- [How we measure](https://digitalgemology.com/about/how-we-measure)
- [What we do not model](https://digitalgemology.com/about/how-we-measure/limits)

[All 328 terms](https://digitalgemology.com/learn/glossary)