# volume rendering for unstructured grid returns error, how to solve that?
**URL:** https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993
**Category:** ParaView Support
**Created:** [April 18, 2021, 12:28pm UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993 "2021-04-18T12:28:39Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@IrinaZhuang](https://discourse.paraview.org/u/IrinaZhuang)
#### Post date: [April 18, 2021, 12:28pm UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/1 "2021-04-18T12:28:39Z")
Hi,
I created a vtu file, which originally was csv-like file, its format: x y z + point data. However, when trying to do volume rendering, I encountered error: vtkOpenGLProjectedTetrahedraMapper (000002413E153CE0): Encountered non-tetrahedra cell!
How can I fixed this problem except doing interpolator? Doing this will lose some high frequency information. And is the method paraview use is pre-integrated transfer function? Someone told me this generate higher quality result than other method.Thanks!
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 19, 2021, 8:09am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/2 "2021-04-19T08:09:40Z")
Use Tetrahadralize filter ?
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### Author:  [@IrinaZhuang](https://discourse.paraview.org/u/IrinaZhuang)
#### Post date: [April 19, 2021, 8:25am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/4 "2021-04-19T08:25:03Z")
I’ve tried, but the error is still there.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 19, 2021, 8:30am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/5 "2021-04-19T08:30:18Z")
Please share your data.
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### Author:  [@IrinaZhuang](https://discourse.paraview.org/u/IrinaZhuang)
#### Post date: [April 19, 2021, 8:39am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/6 "2021-04-19T08:39:54Z")
[mine.vtu](https://discourse.paraview.org/uploads/short-url/tTghk2csiTrD3akNyL1kNbNH37J.vtu) (7.3 KB)
This is part of the complete version and shares all the problem I met in the complete one
Original one is too big to upload and test
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 19, 2021, 8:45am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/7 "2021-04-19T08:45:01Z")
Your dataset contains only points with all the same scalars values.
You cannot volume render this.
You can convert your points into a volumic datasets using Delaunay3D filter, that will fix your initial issue, but your data is still identical everywhere, which cant be volume renderered.
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### Author:  [@IrinaZhuang](https://discourse.paraview.org/u/IrinaZhuang)
#### Post date: [April 19, 2021, 9:04am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/8 "2021-04-19T09:04:28Z")
sorry, that part was too small to show the differences, this is a larger sample[mine2.vtu](https://discourse.paraview.org/uploads/short-url/iDJVi6ELWfVFP7nh3sqyEJpQYGa.vtu) (3.7 MB)
And the original one has over 10 million points, is delaunay3d possible to produce result? Or are there lighter way?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 19, 2021, 9:05am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/9 "2021-04-19T09:05:53Z")
> is delaunay3d possible to produce result?
It should work. But ResampleToImage could be a more efficient way.
> Or are there lighter way?
Providing the topology in your original dataset if you already have it
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 19, 2021, 9:07am UTC](https://discourse.paraview.org/t/volume-rendering-for-unstructured-grid-returns-error-how-to-solve-that/6993/10 "2021-04-19T09:07:57Z")
Actually, I’m looking at your second dataset, delaunay 3d will give you unsatisfactory results with this kind of disconnected unstrucutred grid.
Even Resampling to an image wont work great.
In order to volume render, you need to provide a topology.
Allternatively, do not use vol