# How to save selection as polydata vtk file instead of unstructured grid vtk file?
**URL:** https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625
**Category:** ParaView Support
**Tags:** vtk
**Created:** [October 27, 2022, 11:06pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625 "2022-10-27T23:06:14Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Gening\_Dong](https://discourse.paraview.org/u/Gening_Dong)
#### Post date: [October 27, 2022, 11:06pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/1 "2022-10-27T23:06:14Z")
Hi,
I want to extract some points from a tetrahedral mesh and save the selection as a `Polydata vtk` file. I used `Select Points Through` and then `Extract Selection`. I try to save it as `vtk` file, but it can only be saved as `Unstructured Grid vtk`. How can I save it as `Polydata vtk`?
Thanks!
Gening
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### Author:  [@jfausty](https://discourse.paraview.org/u/jfausty)
#### Post date: [October 28, 2022, 2:49pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/2 "2022-10-28T14:49:07Z")
Hi @Gening_Dong,
Welcome to the ParaView discourse and thanks for posting about your problem!
The “Extract Surface” filter will take you from a `vtkUnstructuredGrid` to a `vtkPolyData` keeping in mind that a `vtkPolyData` is necessarily a geometrical object with dimension inferior to 3.
Hope that helps!
Best regards,
Julien
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### Author:  [@jfausty](https://discourse.paraview.org/u/jfausty)
#### Post date: [November 2, 2022, 10:17am UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/4 "2022-11-02T10:17:42Z")
Hi @Gening_Dong,
May I ask why you need the extraction to be a `vtkPolyData` and not a `vtkUnstructuredGrid`?
If you are only interested in the points you can use the “Convert To Point Cloud” filter on the extracted `vtkUnstructuredGrid` to obtain a `vtkPolyData` containing only points.
Best regards,
Julien
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### Author:  [@Gening\_Dong](https://discourse.paraview.org/u/Gening_Dong)
#### Post date: [November 2, 2022, 2:28pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/5 "2022-11-02T14:28:14Z")
Hi, I’d like to make the extracted points into a separate surface for a specific boundary condition in a CFD/FSI simulation. I think I should select cells instead of points. Thanks for the suggestion.
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### Author:  [@jfausty](https://discourse.paraview.org/u/jfausty)
#### Post date: [November 2, 2022, 5:26pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/6 "2022-11-02T17:26:35Z")
Hi again @Gening_Dong,
I think I see what you would like to do.
You might want to select the cells, perform an `Extract Selection` and then an `Extract Surface` to only get the outside surface of that selection as a `vtkPolyData`.
Hope that helps!
Best regards,
Julien
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### Author:  [@Gening\_Dong](https://discourse.paraview.org/u/Gening_Dong)
#### Post date: [November 2, 2022, 9:10pm UTC](https://discourse.paraview.org/t/how-to-save-selection-as-polydata-vtk-file-instead-of-unstructured-grid-vtk-file/10625/7 "2022-11-02T21:10:31Z")
That’s exactly what I want to do and it works! Thanks so much for your help!