# Extracting a surface

**URL:** https://discourse.paraview.org/t/extracting-a-surface/3386
**Category:** ParaView Support
**Created:** [January 23, 2020, 10:23am UTC](https://discourse.paraview.org/t/extracting-a-surface/3386 "2020-01-23T10:23:15Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![vishruthdilip](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/v/f9ae1b/32.png) [@vishruthdilip](https://discourse.paraview.org/u/vishruthdilip)
#### Post date: [January 23, 2020, 10:23am UTC](https://discourse.paraview.org/t/extracting-a-surface/3386/1 "2020-01-23T10:23:15Z")

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Hi,  
I need to create a surface across which I need to measure the mass flow rate.  
My geometry is such that I have two circular surfaces, the edges of which are concentric circles.

![image](https://discourse.paraview.org/uploads/default/original/2X/9/97051ee88e649d5b011006723c9d7530a9ec1786.png)

For instance, I need to extract the yellow surface in the above image. I need to plot the mass flow rate across this surface.  
What’s the best way to do this. And also, since I use the Lagrange approach, and my solver is Point based, I can not use Extract Selection and plot the data.  
Any help will be appreciated.

Thank you

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### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [January 23, 2020, 4:11pm UTC](https://discourse.paraview.org/t/extracting-a-surface/3386/2 "2020-01-23T16:11:47Z")

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I’m not sure I totally understand what you are trying to do. I don’t think you want to extract the yellow pixels in the image you sent. It would help if you sent a screenshot of the data in ParaView.

I assume you have a planar surface defined by polygons in the shape you described. I mocked something like that in ParaView that looks like this.

 ![Capture1](https://discourse.paraview.org/uploads/default/original/2X/9/95b23c5e2601b75ce64bb774c5c4b1da8b780b2c.png)

You can extract the yellow ring by using the `Clip` filter to remove the pink circle. Do this by adding the `Clip` ![pqClip24](https://discourse.paraview.org/uploads/default/original/2X/6/6a980e5ccc1ba5975c5813237bca3b488c0e3e2d.png) filter. Change `Clip Type` to `Sphere` and then adjust the `Center` and `Radius` so that the drawn sphere is over the pink circle and not the yellow ring.

 ![Capture2](https://discourse.paraview.org/uploads/default/original/2X/c/c9c6d303634dcec1dc235e3ca7923dfd49336bb1.png)

Now turn off the `Invert` option and finally click `Apply`. The pink circle will now be clipped out.

 ![Capture3](https://discourse.paraview.org/uploads/default/original/2X/7/7f7eb72c10be5e8291e52d06240c5c388960a571.png)

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### Author: ![Lemon](https://discourse.paraview.org/user_avatar/discourse.paraview.org/lemon/32/16166_2.png) [@Lemon](https://discourse.paraview.org/u/Lemon)
#### Post date: [May 16, 2025, 2:04am UTC](https://discourse.paraview.org/t/extracting-a-surface/3386/3 "2025-05-16T02:04:25Z")

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Sorry, I’m going to interrupt here. I want to know how to calculate the distance between the top and bottom of the yellow area, that is, the thickness?