# VTK file visualization and surface/volume mesh extraction

**URL:** https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757
**Category:** ParaView Support
**Tags:** vtk
**Created:** [January 11, 2022, 11:17pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757 "2022-01-11T23:17:20Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![Emil](https://discourse.paraview.org/user_avatar/discourse.paraview.org/emil/32/8340_2.png) [@Emil](https://discourse.paraview.org/u/Emil)
#### Post date: [January 11, 2022, 11:17pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757/1 "2022-01-11T23:17:20Z")

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Hello Gentle people

I am facing an issue when trying to create a stl surface from vtk file generated from a open source program. I am not an expert on the program that outputs the vtk file nor it has many parameters that i can control. Opening the file in paraview does show closed surfaces and is exactly what i need but in an stl format.

- Opened file in ParaView
- Used paraview to extract surface and then exported the surface file as stl.
- Open Stl in meshmixer

It seems the stl has alternating face normals. Please help me to solve this problem.

 ![1 (1)](https://discourse.paraview.org/uploads/default/original/2X/c/c4466b7a83d7d9c266d6803ecac027025a24ecfd.png)  
 ![2 (1)](https://discourse.paraview.org/uploads/default/original/2X/8/8a8aab92735153df6872894a4e62b82b46a6a6a0.jpeg)

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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: [January 11, 2022, 11:23pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757/2 "2022-01-11T23:23:14Z")

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GenerateSurfaceNormals filter maybe ?

This may be an issue in mesh mixer though.

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### Author: ![Emil](https://discourse.paraview.org/user_avatar/discourse.paraview.org/emil/32/8340_2.png) [@Emil](https://discourse.paraview.org/u/Emil)
#### Post date: [January 12, 2022, 2:30pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757/3 "2022-01-12T14:30:13Z")

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I have exported the stl in other programs (CFD solvers) and the alternating face normal strips are also shown there. So i do not think the problem is with meshmixer.

Could you please explain the step where i should apply the GenerateSurfaceNormals filter?

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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: [January 12, 2022, 2:38pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757/4 "2022-01-12T14:38:43Z")

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Filters - \> Alphabetical → GenerateSurfaceNormals → Apply

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### Author: ![Emil](https://discourse.paraview.org/user_avatar/discourse.paraview.org/emil/32/8340_2.png) [@Emil](https://discourse.paraview.org/u/Emil)
#### Post date: [January 18, 2022, 3:20pm UTC](https://discourse.paraview.org/t/vtk-file-visualization-and-surface-volume-mesh-extraction/8757/5 "2022-01-18T15:20:21Z")

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Thanks. i applied this filter after GenerateSurface filter and that solved the problem.