# extract the outer surface of the tube and show it as a rectangular surface
**URL:** https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324
**Category:** ParaView Support
**Tags:** vtk
**Created:** [September 15, 2022, 11:32am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324 "2022-09-15T11:32:14Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@mohsen.rock](https://discourse.paraview.org/u/mohsen.rock)
#### Post date: [September 15, 2022, 11:32am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/1 "2022-09-15T11:32:14Z")
Dear experts,
I have a 3D domain in the form of a tube (see the following figure). I would like to know if there is a way to extract the outer boundary of my tube and show it in the form of a rectangular 2D surface. This will help a lot in demonstrating my results.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 15, 2022, 11:37am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/2 "2022-09-15T11:37:26Z")
Hi @mohsen.rock ,
A screenshot of what you want to do would be nice.
Maybe FeatureEdges ?
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### Author:  [@mohsen.rock](https://discourse.paraview.org/u/mohsen.rock)
#### Post date: [September 15, 2022, 11:43am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/3 "2022-09-15T11:43:51Z")
Hi @mwestphal
Thanks for the quick response. Here is a sketch of what I would like to do (sorry for the awful drawing).
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 15, 2022, 11:50am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/4 "2022-09-15T11:50:46Z")
You are looking for a Silhouette filter, sadly none have been integrated in ParaView yet. You can find an (old) discussion about it here: [[Paraview] Contribution : Silhouette edges filter](https://paraview.paraview.narkive.com/CRiGBBgD/contribution-silhouette-edges-filter)
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### Author:  [@mohsen.rock](https://discourse.paraview.org/u/mohsen.rock)
#### Post date: [September 15, 2022, 11:51am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/5 "2022-09-15T11:51:47Z")
Indeed, very sad. Thank you anyway.
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### Author:  [@spyridon97](https://discourse.paraview.org/u/spyridon97)
#### Post date: [September 16, 2022, 1:36pm UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/6 "2022-09-16T13:36:03Z")
It just needs to be exposed in ParaView? I see [https://vtk.org/doc/nightly/html/classvtkPolyDataSilhouette.html](https://vtk.org/doc/nightly/html/classvtkPolyDataSilhouette.html). If yes, @cory.quammen would you like me to do that?
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### Author:  [@cory.quammen](https://discourse.paraview.org/u/cory.quammen)
#### Post date: [September 16, 2022, 1:44pm UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/7 "2022-09-16T13:44:45Z")
Correct me if I am wrong, but this looks like you want to unwrap the cylinder, i.e., cut it down its length and then flatten it out.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 16, 2022, 1:57pm UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/8 "2022-09-16T13:57:12Z")
Maybe ? I’m not entirely sure.
@spyridon97 my understanding is that this filter needs access to the camera, which ParaView cant provide.
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### Author:  [@mohsen.rock](https://discourse.paraview.org/u/mohsen.rock)
#### Post date: [September 16, 2022, 4:30pm UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/9 "2022-09-16T16:30:36Z")
Yes exactly. I managed to do it by using the calculator and transforming the coordinates of the tube outer surface into a rectangular plane.
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### Author:  [@roland](https://discourse.paraview.org/u/roland)
#### Post date: [September 22, 2022, 10:41am UTC](https://discourse.paraview.org/t/extract-the-outer-surface-of-the-tube-and-show-it-as-a-rectangular-surface/10324/10 "2022-09-22T10:41:12Z")
Hi @mohsen.rock,
In this post I explain my steps whenever I need to unwrap cylinder. Maybe it is of use to you too.
> [@Unwrapping a cylinder](https://discourse.paraview.org/t/unwrapping-a-cylinder/8731/2):
>
> Can it be that your surface is folded back on it self because you use an atan function instead of atan2? I don’t know if atan2 is available now, but it wasn’t before, so I used to calculate it myself with a Calculator filter: if(coordsX\>0,atan(coordsY/coordsX), if(coordsX\<0, if(coordsY\<0,atan(coordsY/coordsX)-4\*atan(1),atan(coordsY/coordsX) +4 \*atan(1)), if(coordsY\>0, 2 \*atan(1), if(coordsY\<0, -2 \*atan(1),0)))) Then apply a [-pi, pi] threshold on the resulting angle (which I called theta). …
Kind regards,
Roland