# Cannot create streamlines from groundwater heads .vtu-file
**URL:** https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102
**Category:** ParaView Support
**Created:** [September 30, 2021, 10:21am UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102 "2021-09-30T10:21:42Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@KristinaGum](https://discourse.paraview.org/u/KristinaGum)
#### Post date: [September 30, 2021, 10:21am UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/1 "2021-09-30T10:21:42Z")
Hi everyone,
I am having trouble to create stream lines from a vtu file which contains groundwater head values. It displays fine but the stream tracer filter is disabled. I researched online and found that it might be necessary to create the vectors first. To do that I tried to use the programmable filter (as advised here) but it gives me the error that U and V are unknown. When I look at the information tab at the file I noticed, that there are no data arrays and the dimensions (number of cells and points) are set to zero. This surprises me because the vtu is clearly displayed with the correct values. I have little experience working on vtu files, so I don’t know
what’s wrong with it. I also have a .pvd file created with the same code, however Paraview throws an error when I load it:
```auto
ERROR: In C:\glr\builds\paraview\paraview-ci\build\superbuild\paraview\src\VTKExtensions\IOCore\vtkXMLCollectionReader.cxx, line 444
vtkPVDReader (000001E4BA15BC90): Could not determine the data type for the first dataset. Please make sure this file format is supported.
ERROR: In C:\glr\builds\paraview\paraview-ci\build\superbuild\paraview\src\VTK\Common\ExecutionModel\vtkExecutive.cxx, line 753
vtkPVCompositeDataPipeline (000001E4B3873960): Algorithm vtkPVDReader(000001E4BA15BC90) returned failure for request: vtkInformation (000001E4AB30CB00)
Debug: Off
Modified Time: 2596371
Reference Count: 1
Registered Events: (none)
Request: REQUEST_DATA_OBJECT
FORWARD_DIRECTION: 0
ALGORITHM_AFTER_FORWARD: 1
```
So maybe the file is damaged? If needed I can provide the data via google drive or so…
Thanks!
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 30, 2021, 12:58pm UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/2 "2021-09-30T12:58:32Z")
please share the files
---
### Author:  [@KristinaGum](https://discourse.paraview.org/u/KristinaGum)
#### Post date: [September 30, 2021, 1:13pm UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/3 "2021-09-30T13:13:52Z")
should be available here
[https://drive.google.com/drive/folders/1l4qM24Bj06Ca3q8lpgt6jB8aGN7XF9kw?usp=sharing](https://drive.google.com/drive/folders/1l4qM24Bj06Ca3q8lpgt6jB8aGN7XF9kw?usp=sharing)
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [September 30, 2021, 1:55pm UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/4 "2021-09-30T13:55:52Z")
Here is your corrected .pvd file.
[spandau-flopy\_head.pvd](https://discourse.paraview.org/uploads/short-url/vtovhNEEUg6OqrSFpRlfZlQggcV.pvd) (287 Bytes)
The filename was not complete
---
### Author:  [@KristinaGum](https://discourse.paraview.org/u/KristinaGum)
#### Post date: [September 30, 2021, 5:14pm UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/5 "2021-09-30T17:14:57Z")
Thanks a lot!!
However, how do I solve the original issue now? I assumed that the files might be somehow connected - which I guess is not the case. Is it actually possible to apply the stream tracer filter on the .vtu file or am I making a mistake here?
---
### Author:  [@KristinaGum](https://discourse.paraview.org/u/KristinaGum)
#### Post date: [October 1, 2021, 8:24am UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/6 "2021-10-01T08:24:44Z")
When I follow these instructions on either of the two files I get the error message below. It seems to be related to the names of the vector. How do I find out which name would be the correct one for my file?
> [@Stream Tracer grayed out](https://discourse.paraview.org/t/stream-tracer-grayed-out/4338/3):
>
> Thank you Cory for the response. I just checked out and found that the Cell Data to Point Data filter is grayed out too! I guess I am doing some basic mistakes?!
```auto
Traceback (most recent call last):
File "C:\Program Files\ParaView 5.9.0-RC2-Windows-Python3.8-msvc2017-64bit\bin\Lib\site-packages\paraview\detail\calculator.py", line 203, in execute
retVal = compute(inputs, expression, ns=variables)
File "C:\Program Files\ParaView 5.9.0-RC2-Windows-Python3.8-msvc2017-64bit\bin\Lib\site-packages\paraview\detail\calculator.py", line 146, in compute
retVal = eval(subEx, globals(), mylocals)
File "", line 1, in
NameError: name 'U' is not defined
```
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 4, 2021, 8:03am UTC](https://discourse.paraview.org/t/cannot-create-streamlines-from-groundwater-heads-vtu-file/8102/7 "2021-10-04T08:03:00Z")
> [@KristinaGum](#):
>
> Is it actually possible to apply the stream tracer filter on the .vtu file or am I making a mistake here?
Your data does not contain any point based vectors, so you can’t apply a stream tracer on it.