# Isosurface extraction based on condition
**URL:** https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921
**Category:** ParaView Support
**Created:** [September 2, 2021, 6:22pm UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921 "2021-09-02T18:22:33Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Akash](https://discourse.paraview.org/u/Akash)
#### Post date: [September 2, 2021, 6:22pm UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/1 "2021-09-02T18:22:33Z")
These are isosurface with plot of alpha\_water on them. How to remove the surface that is fully blue(alpha\_water\<0.2). If the surface has mix of blue and red I need those surfaces. In “Find data” tool we can choose cells/points with a condition similarly is there a tool to choose a surface with a condition?
Here is the plot:
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 3, 2021, 8:05am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/2 "2021-09-03T08:05:36Z")
use Treshold filter.
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### Author:  [@Akash](https://discourse.paraview.org/u/Akash)
#### Post date: [September 3, 2021, 9:19am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/3 "2021-09-03T09:19:28Z")
Thanks but it also removes the surfaces having both air and water.
Here is before threshold:
Then after applying threshold 0.5 to 1, surfaces completely blue is removed but also the one with mix of red and blue which I need
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 3, 2021, 9:24am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/4 "2021-09-03T09:24:15Z")
What is your question here ?
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### Author:  [@Akash](https://discourse.paraview.org/u/Akash)
#### Post date: [September 3, 2021, 9:28am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/5 "2021-09-03T09:28:43Z")
Sorry, so in this plot I have multiple 3d surfaces. For coloring I plotted the alpha\_water on them. There are surface which has red and white colors which indicate pure water (category 1) , there are surfaces with blue and red which indicate water and air(category 2). Finally third category which is completely blue that is fully air. I have to remove last category surface and keep the other two.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 3, 2021, 9:36am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/6 "2021-09-03T09:36:28Z")
Uncheck “All Scalars”
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### Author:  [@Akash](https://discourse.paraview.org/u/Akash)
#### Post date: [September 3, 2021, 10:22am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/7 "2021-09-03T10:22:06Z")
Thanks, I think it worked. What does "All Scalar " do?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 3, 2021, 11:39am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/8 "2021-09-03T11:39:19Z")
> If the value of this property is 1, then a cell is only
> included in the output if the value of the selected array for all its
> points is within the threshold. This is only relevant when thresholding
> by a point-centered array.
Just hover with your mouse on the option to see the tooltip documentation.
Alternatively, click on the ? button.
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### Author:  [@Akash](https://discourse.paraview.org/u/Akash)
#### Post date: [September 3, 2021, 11:43am UTC](https://discourse.paraview.org/t/isosurface-extraction-based-on-condition/7921/9 "2021-09-03T11:43:20Z")
Sure, thank you