# About 3D Models Types

> The difference between CAD and polygonal 3D models in Asset Transformer Studio

![CAD vs Mesh](/api/media?file=/asset-transformer-studio/2026.5.0/media/PiXYZ-Software_CADvsMesh.jpg)

CAD models inherited from CAD software (CATIA, NX, SolidWorks, Alias, STEP…) are not [tessellated](./about-tessellation.md). They contain exact parametric geometries, also called BRep, NURBS, CSG…

A CAD body (closed volume) or CAD surface (open shell surface) is composed of CAD faces (also called patches), delimited by boundaries (see [Glossary](./glossary.md)).

> **Note:**
>
> Useful links about CAD vocabulary: [CAD](https://en.wikipedia.org/wiki/Computer-aided_design), [BRep](https://en.wikipedia.org/wiki/Boundary_representation), [NURBS](https://en.wikipedia.org/wiki/Non-uniform_rational_B-spline), [PMI](https://en.wikipedia.org/wiki/Product_and_manufacturing_information), [CAD Data Exchange](https://en.wikipedia.org/wiki/CAD_data_exchange).

To be displayed in a 3D application, **CAD faces need to be translated into tessellated surfaces, also called meshes**.

A mesh is composed of multiple connected polygons, or triangles (1 polygon generally equals 2 coplanar triangles), forming a discretized geometry that is understandable by a GPU, to be rendered in a 3D application.

Moreover, CAD models can contain additional engineering and design data (Metadata, PMI…), which can be very useful to perform a targeted data preparation process based on targeted properties.

DCC software (Maya, 3DS Max, Blender, Modo…) natively create **tessellated geometries** (often referred to as polygonal models), which can be exported as FBX files for example, to be reimported in Asset Transformer Studio for further optimization.

Note that these meshes often come with attributes like normals and UVs (texture coordinates used to display textures on meshes), which can either be kept or recreated in Asset Transformer Studio.

> **Note:**
>
> To learn about a mesh and its attributes, have a look at the page [Anatomy of a Mesh](https://docs.unity3d.com/Manual/AnatomyofaMesh.html) in Unity documentation! See also [Polygon Mesh](https://en.wikipedia.org/wiki/Polygon_mesh) and [About Face and Vertex Normals](./about-face-and-vertex-normals.md).

## Related topics

* [Supported File Formats](../supported-file-formats)
* [About the Product Structure (Tree)](./about-the-product-structure-tree.md)
* [About Tessellation](./about-tessellation.md)
* [About Decimation](./about-decimation.md)
* [About Face and Vertex Normals](./about-face-and-vertex-normals.md)