---
title: "Planar facet: meaning in gemology"
description: "A planar facet is a facet that lies exactly in one flat plane. Real cut stones and our models have planar facets; curved or smoothed display models do not."
url: https://digitalgemology.com/learn/glossary/planar-facet
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Cutting and files

# Planar facet

Also called flat facet

A planar facet is a facet that lies exactly in one flat plane. Real cut stones and our models have planar facets; curved or smoothed display models do not.

## In more detail

A gem refracts correctly only when its facets are truly flat. A flat facet keeps a beam together, and a curved one spreads it. So a rounded, smoothed or scanned model cannot be measured as a cut stone.

## How we measure it

Our tools group a model's triangles into facets by the plane they lie on. A model that breaks into more than 2,000 flat pieces counts as a scan or a smooth shape. The tools do not measure it as a cut.

## Related terms

- [Facet](https://digitalgemology.com/learn/glossary/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.
- [Mesh](https://digitalgemology.com/learn/glossary/mesh): A mesh describes a 3D surface as many small flat triangles joined at their edges. STL, OBJ, FBX and GLB files store a mesh.
- [Convex](https://digitalgemology.com/learn/glossary/convex): 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.
- [Measure your own stone](https://digitalgemology.com/learn/glossary/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.

## Learn more

- [Who uses our files](https://digitalgemology.com/about/files)
- [Your own file](https://digitalgemology.com/about/how-we-measure/your-own-file)
- [The 3D models](https://digitalgemology.com/about/how-we-measure/3d-models)

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