# Error when using extract region surface filter

**URL:** https://discourse.paraview.org/t/error-when-using-extract-region-surface-filter/8312
**Category:** ParaView Support
**Tags:** vtk
**Created:** [November 3, 2021, 9:39am UTC](https://discourse.paraview.org/t/error-when-using-extract-region-surface-filter/8312 "2021-11-03T09:39:02Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Aminkb](https://discourse.paraview.org/user_avatar/discourse.paraview.org/aminkb/32/7867_2.png) [@Aminkb](https://discourse.paraview.org/u/Aminkb)
#### Post date: [November 3, 2021, 9:39am UTC](https://discourse.paraview.org/t/error-when-using-extract-region-surface-filter/8312/1 "2021-11-03T09:39:02Z")

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Hi,  
I have an unstructured grid data vtk file of a volumetric mesh. I’m trying to extract region surfaces from that mesh, but it’s returning an error saying what I have is polydata while this filter needs an unstructured grid.  
Anyone knows why this might be happening?

To give a bit of a context, the vtk file itself was generated by changing the points data of a template vtk file that has the connectivity list I need. The region surface extraction works fine in the template.

Can having more than one space (tap) between the coordinates cause this issue?

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### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [November 3, 2021, 9:50am UTC](https://discourse.paraview.org/t/error-when-using-extract-region-surface-filter/8312/2 "2021-11-03T09:50:25Z")

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please share data and name of the filter you are trying to use

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### Author: ![Aminkb](https://discourse.paraview.org/user_avatar/discourse.paraview.org/aminkb/32/7867_2.png) [@Aminkb](https://discourse.paraview.org/u/Aminkb)
#### Post date: [November 3, 2021, 11:47am UTC](https://discourse.paraview.org/t/error-when-using-extract-region-surface-filter/8312/3 "2021-11-03T11:47:15Z")

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@mwestphal Thanks for responding promptly. This is the data file [vtk file](https://leeds365-my.sharepoint.com/:u:/g/personal/mn15akb_leeds_ac_uk/ESGqiyYJb79EgPQmqIXpApIBrP-_pX96B5nsZHPYV6mO3g?e=KnRGQf).  
the filter name is Extract region surface. The problem was that I could not select the data I want to begin with (using the select data) tool.

An update…I found a way to make the coordinates closer with no extra whitespace, now I can use the filter correctly. It seems the extra whitespace was causing an issue.