# plot over line on a slice (vtu) doesn't work
**URL:** https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366
**Category:** ParaView Support
**Created:** [February 2, 2021, 2:02pm UTC](https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366 "2021-02-02T14:02:19Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@gbug](https://discourse.paraview.org/u/gbug)
#### Post date: [February 2, 2021, 2:02pm UTC](https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366/1 "2021-02-02T14:02:19Z")
Hi! I have a pretty large 3D dataset (vtu) and would like to speed-up postprocessing by making the slices (2D, vtu). Then I 'd like to make a plot over that slices however it doesn’t work – output data arrays are empty. The test data/state file are here: [https://drive.google.com/drive/folders/1kODCozNYlh9b65bqJPyWURzOUsWMsCEx?usp=sharing](https://drive.google.com/drive/folders/1kODCozNYlh9b65bqJPyWURzOUsWMsCEx?usp=sharing)
The problem looks the same as reported here [Plot over line gives NaN](https://discourse.paraview.org/t/plot-over-line-gives-nan/2207) but it doesn’t. The line could be anywhere across the dataset, not only near the boundary, the output still be empty.
ParaView 5.9.0 downloaded from the site. OS: Debian testing amd64, DE: KF5
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 2, 2021, 2:59pm UTC](https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366/2 "2021-02-02T14:59:15Z")
Definitely a bug in my opinion. I was able to obtain some results by using a polyline source and resample with dataset, but complex to use.
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [February 2, 2021, 9:24pm UTC](https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366/3 "2021-02-02T21:24:04Z")
I do believe this is the same problem. The issue is that you are sampling a 2D surface in a 3D space. I agree that it would be better to make the polygon probing less sensitive to these error, but I couldn’t get sampling by a polyline source to work for me.
I was able to get it to work by shifting your plane to the z=0 plane. Your plane is currently at z=0.001, a number that is not completely representable in IEEE floating points. Here is another state file that shifts your data and seems to make it work:
[translate-plane.pvsm](https://discourse.paraview.org/uploads/short-url/67GHbxW7EFVLmV8zIXuIjqYZb4j.pvsm) (457.2 KB)
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### Author:  [@gbug](https://discourse.paraview.org/u/gbug)
#### Post date: [February 4, 2021, 9:48am UTC](https://discourse.paraview.org/t/plot-over-line-on-a-slice-vtu-doesnt-work/6366/4 "2021-02-04T09:48:36Z")
Thanks, Kenneth and Mathieu! Both workarounds are acceptable (scripts do the work for me) however shifting is simpler to explain.