# How to use Eigen inside VTK

**URL:** https://discourse.vtk.org/t/how-to-use-eigen-inside-vtk/10047
**Category:** Support
**Created:** [December 2, 2022, 2:38pm UTC](https://discourse.vtk.org/t/how-to-use-eigen-inside-vtk/10047 "2022-12-02T14:38:36Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Ruooo](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@Ruooo](https://discourse.vtk.org/u/Ruooo)
#### Post date: [December 2, 2022, 2:38pm UTC](https://discourse.vtk.org/t/how-to-use-eigen-inside-vtk/10047/1 "2022-12-02T14:38:36Z")

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Hi, I’m trying to use Eigen for some geometry computing, but I don’t know how to use the VTK third-party module and how to include the Eigen header.  
For now, In CMakeLists, I put vtkeigen in the find\_package, and include vtk\_eigen.h. But still quite confused about what’s next. Please share some advice about how to use Eigen. Thank you in advance 😃

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### Author: ![Ruooo](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@Ruooo](https://discourse.vtk.org/u/Ruooo)
#### Post date: [December 5, 2022, 4:08pm UTC](https://discourse.vtk.org/t/how-to-use-eigen-inside-vtk/10047/2 "2022-12-05T16:08:34Z")

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update, I got the solution, just build vtk with -DVTK\_MODULE\_USE\_EXTERNAL\_vtkeigen=ON