# Unstructured Grid Individual Face Areas
**URL:** https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606
**Category:** ParaView Support
**Created:** [March 3, 2021, 8:11pm UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606 "2021-03-03T20:11:24Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 3, 2021, 8:11pm UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/1 "2021-03-03T20:11:24Z")
I am trying to extract the individual area of each face on an unstructured surface grid from OpenFOAM. I have tried using both the PythonCalculator (area(input[0])) and Quality features but this seems to be limited to just quad and tri elements. All the elements with 5 or more sides are just given an area of -1 (see figure). Is there away to calculate the area of the irregular polygons within paraview?
Thanks in advance,
Ian
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 4, 2021, 8:33am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/2 "2021-03-04T08:33:46Z")
I’m afraid area is only implemented for quad and tri. This could be implemented though.
[https://vtk.org/doc/nightly/html/classvtkMeshQuality.html](https://vtk.org/doc/nightly/html/classvtkMeshQuality.html)
Alternatively, you could triangulate your dataset first.
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### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 4, 2021, 8:46am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/3 "2021-03-04T08:46:22Z")
Thank you for your reply Mathieu.
I was curious how the integrate variables command works when you can’t extract the areas to integrate over.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 4, 2021, 8:52am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/4 "2021-03-04T08:52:12Z")
What do you mean ?
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### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 4, 2021, 9:10am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/5 "2021-03-04T09:10:59Z")
As an example, if you have a body and want to integrate the pressure over the whole surface and multiply by normals to get lift and drag (not what I am doing in this case but an example). I assumed it was calculating:
Lift = sum of (face pressure \* face area \* Normal.z)
Drag = sum of (face pressure \* face area \* Normal.x)
If ParaView doesn’t currently extract the face area, does it use some other algorithm to do the integration?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 4, 2021, 9:18am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/6 "2021-03-04T09:18:05Z")
Which filter are you using to perform this integration ?
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### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 4, 2021, 9:23am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/7 "2021-03-04T09:23:01Z")
Filters \> Data Analysis \> Integrate Variables
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [March 4, 2021, 9:34am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/8 "2021-03-04T09:34:34Z")
Looks like vtkIntegrateAttributes and vtkMeshQuality both contains area computation code.
vtkIntegrateAttributes implementation seems more complete:
[https://gitlab.kitware.com/vtk/vtk/-/blob/master/Filters/Parallel/vtkIntegrateAttributes.cxx](https://gitlab.kitware.com/vtk/vtk/-/blob/master/Filters/Parallel/vtkIntegrateAttributes.cxx)
IMO, this should be fixed the this method of cell computation should be added to vtkCell.
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### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 4, 2021, 9:42am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/9 "2021-03-04T09:42:49Z")
Mathieu,
Looking at the IntegratePolygon it looks like it is just breaking each polygon down in to triangles to calculate the areas. I have used this functionality in the past to get an idea whether my lift and drag calculations were close and was concerned that it was missing out all the polygons.
I am using v5.2.0 currently and I saw [this](https://discourse.paraview.org/t/how-to-get-force-distribution-on-body/5815) post, and wondered if the cellsize was a feature in a newer version that solves this problem.
Thank you for your help, Ian
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### Author:  [@Ian\_Roberts](https://discourse.paraview.org/u/Ian_Roberts)
#### Post date: [March 4, 2021, 10:21am UTC](https://discourse.paraview.org/t/unstructured-grid-individual-face-areas/6606/10 "2021-03-04T10:21:11Z")
I have used 5.2.9 now and the cellSize variable works well.
The function should probably be included in the area(inputs[0]) function in the python calculator too.