# About Face and Vertex Normals

> How face and vertex normals work in Asset Transformer Studio meshes

![Normals illustration](/api/media?file=/asset-transformer-studio/2026.5.0/media/NewItem130.png)

When talking about meshes in Asset Transformer Studio (be it mesh generation using [Tessellation](./about-tessellation.md), or mesh optimization with [Decimation](./about-decimation.md) for example), it is important to understand how a mesh is built.

Basically, a mesh is made of a collection of polygons (triangles, quadrangles, n-gons…), delimited by edges and vertices.

A closed polygon defines a **face**, which can be facing in one direction or the other. The **face normal** defines its direction.

A closed polygon has **vertices** at each corner, and each vertex has its own normal. The **vertex normal** defines how virtual light will bounce off the mesh, defining a smoothing for the underlying mesh.

The normals of the vertices are attributes of the mesh.

Additionally to normals, a mesh can have other attributes like UVs, tangents, binormals, etc. that define how it will behave when rendered in a 3D application.

Please have a look at the following pages to learn more about meshes and mesh attributes:

* [Anatomy of a Mesh](https://docs.unity3d.com/Manual/AnatomyofaMesh.html) in Unity documentation
* [Introduction to normal maps](https://docs.unity3d.com/Documentation/Manual/StandardShaderMaterialParameterNormalMap.html) in Unity documentation
* [Polygon Mesh](https://en.wikipedia.org/wiki/Polygon_mesh) on Wikipedia