# Extracting data on a surface
**URL:** https://discourse.paraview.org/t/extracting-data-on-a-surface/9084
**Category:** ParaView Support
**Created:** [February 28, 2022, 8:58am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084 "2022-02-28T08:58:20Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@spillai](https://discourse.paraview.org/u/spillai)
#### Post date: [February 28, 2022, 8:58am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/1 "2022-02-28T08:58:20Z")
Hello
I have a CFD solution on an unstructured grid and I want to extract the data on one of the bounding surfaces. I did the following steps.
ExtractSurface \> Clip in X normal \> Clip in Y normal \> Clip at an Z, so that I should have got the bottom surface which is curved.
But I ended up with this
How can I resolve this issue?
Thank you.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 28, 2022, 9:07am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/2 "2022-02-28T09:07:08Z")
> [@spillai](#):
>
> data on one of the bounding surfaces
How do you define this surface mathematically ?
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### Author:  [@spillai](https://discourse.paraview.org/u/spillai)
#### Post date: [February 28, 2022, 9:18am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/3 "2022-02-28T09:18:31Z")
The surface is given by z = quadratic function of x, for x in (0,x0)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 28, 2022, 9:26am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/4 "2022-02-28T09:26:00Z")
Can you use FindData to extract the corresponding Cells then ?
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### Author:  [@spillai](https://discourse.paraview.org/u/spillai)
#### Post date: [February 28, 2022, 9:43am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/5 "2022-02-28T09:43:14Z")
Can I use Find Data to extract all points on the surface? The surface can have millions of solution points.
I should have made it more clear. The surface can be considered as three segments: z=z1 for x\<0; z=f(x^2) in (0,x0); z=z2 for x\>x0.
I tried the SliceAlongPolyLine filter as well. But that did not get me what I wanted.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 28, 2022, 9:47am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/6 "2022-02-28T09:47:59Z")
> [@spillai](#):
>
> Can I use Find Data to extract all points on the surface?
Yes it should
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### Author:  [@spillai](https://discourse.paraview.org/u/spillai)
#### Post date: [March 1, 2022, 5:59am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/8 "2022-03-01T05:59:03Z")
Could you please elaborate on how this can be done? I’d appreciate it.
Also, I am curious why the steps followed my did not work.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 2, 2022, 7:37am UTC](https://discourse.paraview.org/t/extracting-data-on-a-surface/9084/9 "2022-03-02T07:37:29Z")
This how to do it with pvpython.
```auto
QuerySelect(QueryString='your mathematical expression here', FieldType='POINT', InsideOut=0)
```