# FAQ: How does Exchange handle tessellation data while reading a CAD file?

**URL:** <https://forum.techsoft3d.com/t/faq-how-does-exchange-handle-tessellation-data-while-reading-a-cad-file/1498>\
**Category:** HOOPS Exchange\
**Tags:** faq, import, export\
**Created:** [February 22, 2022, 5:00am UTC](https://forum.techsoft3d.com/t/faq-how-does-exchange-handle-tessellation-data-while-reading-a-cad-file/1498 "2022-02-22T05:00:00Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![gabriel.peragine](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.techsoft3d.com/gabriel.peragine/32/1535_2.png) [@gabriel.peragine](https://forum.techsoft3d.com/u/gabriel.peragine)\
**Post date:** [February 22, 2022, 5:00am UTC](https://forum.techsoft3d.com/t/faq-how-does-exchange-handle-tessellation-data-while-reading-a-cad-file/1498/1 "2022-02-22T05:00:00Z")

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HOOPS Exchange supports different modes for reading B-rep and tessellation data from native CAD files, but not all file formats have their data read the same way. In some cases, the tessellation data that exists in the CAD file is read and translated into the PRC data model structure, but in other cases, the tessellation data is generated from the B-rep data.

Read more about [supported file formats](https://docs.techsoft3d.com/exchange/latest/start/supported-formats.html) with HOOPS Exchange.

This table summarizes the different behaviors.

| **File Format** | **Behavior** |
| --- | --- |
| CATIA | If [import options](https://docs.techsoft3d.com/exchange/latest/build/group __a3d__ read.html#ga224bb061827a61351f3c4df119e1b54f) are set to use `kA3DReadTessOnly`, Exchange uses CATIAs internal CGR data for tessellation. |
| Creo | Exchange never reads file tessellation if only tessellation is required, it tessellates then removes geometry. |
| JT | Can support multiple levels of detail of tessellation. One level can be set and read by Exchange. |
| NX | Can have multiple RIs, and tessellation is generated by Exchange. |
| Parasolid | Always tessellates. |
| SolidEdge | Tessellation generated by Exchange. |
| SolidWorks | If [import options](https://docs.techsoft3d.com/exchange/latest/api/A3DSDKEnums_8h.html?highlight=a3dereadgeomtessmode#_CPPv420A3DEReadGeomTessMode) are set to `kA3DReadTessOnly`, Exchange uses file tessellation. |
| STEP | Tessellation generated by Exchange. |