# pvd collection of pvtu files gives blank output

**URL:** https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483
**Category:** ParaView Support
**Created:** [February 2, 2020, 4:01pm UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483 "2020-02-02T16:01:50Z")
**Posts on this page:** 6
**Page:** 1

<div class="post-metadata">

### Author: ![vachan-potluri](https://discourse.paraview.org/user_avatar/discourse.paraview.org/vachan-potluri/32/2919_2.png) [@vachan-potluri](https://discourse.paraview.org/u/vachan-potluri)
#### Post date: [February 2, 2020, 4:01pm UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/1 "2020-02-02T16:01:50Z")

</div>

Hello,

I have many `*.pvtu.*` files which I am able to open and view as a set. I now want to combine this and form a single time series dataset. I have used the following `.pvd` file.

```auto
<?xml version="1.0"?>
<VTKFile type="Collection" version="0.1" byte_order="LittleEndian" compressor="vtkZLibDataCompressor">
<Collection>
<Dataset timestep="0.0" part="0" file="output.pvtu.0"/>
<Dataset timestep="2.28407e-09" part="1" file="output.pvtu.1"/>
<Dataset timestep="4.56808e-09" part="2" file="output.pvtu.2"/>
<Dataset timestep="6.85196e-09" part="3" file="output.pvtu.3"/>
<Dataset timestep="9.13562e-09" part="4" file="output.pvtu.4"/>
<Dataset timestep="1.1419e-08" part="5" file="output.pvtu.5"/>
<Dataset timestep="1.37021e-08" part="6" file="output.pvtu.6"/>
<Dataset timestep="1.59847e-08" part="7" file="output.pvtu.7"/>
<Dataset timestep="1.82664e-08" part="8" file="output.pvtu.8"/>
<Dataset timestep="2.05473e-08" part="9" file="output.pvtu.9"/>
<Dataset timestep="2.28271e-08" part="10" file="output.pvtu.10"/>
<Dataset timestep="2.51059e-08" part="11" file="output.pvtu.11"/>
<Dataset timestep="2.73836e-08" part="12" file="output.pvtu.12"/>
<Dataset timestep="2.96601e-08" part="13" file="output.pvtu.13"/>
</Collection>
</VTKFile>

```

When I read this with Paraview 5.6, I get a blank output. I also tried adding `group=""` in the specification of `Dataset` but couldn’t succeed. What is wrong with my `.pvd` file? What changes should I make to get the desired output?

---

<div class="post-metadata">

### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 3, 2020, 3:01am UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/2 "2020-02-03T03:01:48Z")

</div>

Here is a working .pvd file :

```
<VTKFile type="Collection" version="1.0" byte_order="LittleEndian" header_type="UInt64">
  <Collection>
    <DataSet timestep="0" part="0" file="pvdoutput/pvdoutput_0_0.pvtu"/>
    <DataSet timestep="0.000100074" part="0" file="pvdoutput/pvdoutput_0_1.pvtu"/>
    <DataSet timestep="0.000199905" part="0" file="pvdoutput/pvdoutput_0_2.pvtu"/>
    <DataSet timestep="0.000299964" part="0" file="pvdoutput/pvdoutput_0_3.pvtu"/>
    <DataSet timestep="0.000400087" part="0" file="pvdoutput/pvdoutput_0_4.pvtu"/>
    <DataSet timestep="0.000499919" part="0" file="pvdoutput/pvdoutput_0_5.pvtu"/>
    <DataSet timestep="0.000599935" part="0" file="pvdoutput/pvdoutput_0_6.pvtu"/>
    <DataSet timestep="0.000700049" part="0" file="pvdoutput/pvdoutput_0_7.pvtu"/>
    <DataSet timestep="0.000800035" part="0" file="pvdoutput/pvdoutput_0_8.pvtu"/>
    <DataSet timestep="0.000900061" part="0" file="pvdoutput/pvdoutput_0_9.pvtu"/>
    <DataSet timestep="0.00100001" part="0" file="pvdoutput/pvdoutput_0_10.pvtu"/>
    <DataSet timestep="0.00109998" part="0" file="pvdoutput/pvdoutput_0_11.pvtu"/>
    <DataSet timestep="0.00119993" part="0" file="pvdoutput/pvdoutput_0_12.pvtu"/>
    <DataSet timestep="0.00129999" part="0" file="pvdoutput/pvdoutput_0_13.pvtu"/>
    <DataSet timestep="0.00140009" part="0" file="pvdoutput/pvdoutput_0_14.pvtu"/>
    <DataSet timestep="0.00150004" part="0" file="pvdoutput/pvdoutput_0_15.pvtu"/>
    <DataSet timestep="0.00159992" part="0" file="pvdoutput/pvdoutput_0_16.pvtu"/>
    <DataSet timestep="0.0017" part="0" file="pvdoutput/pvdoutput_0_17.pvtu"/>
    <DataSet timestep="0.00180007" part="0" file="pvdoutput/pvdoutput_0_18.pvtu"/>
    <DataSet timestep="0.00190002" part="0" file="pvdoutput/pvdoutput_0_19.pvtu"/>
    <DataSet timestep="0.00199999" part="0" file="pvdoutput/pvdoutput_0_20.pvtu"/>
    <DataSet timestep="0.00209993" part="0" file="pvdoutput/pvdoutput_0_21.pvtu"/>
    <DataSet timestep="0.00219992" part="0" file="pvdoutput/pvdoutput_0_22.pvtu"/>
    <DataSet timestep="0.00229999" part="0" file="pvdoutput/pvdoutput_0_23.pvtu"/>
    <DataSet timestep="0.00240005" part="0" file="pvdoutput/pvdoutput_0_24.pvtu"/>
    <DataSet timestep="0.00249994" part="0" file="pvdoutput/pvdoutput_0_25.pvtu"/>
    <DataSet timestep="0.00259992" part="0" file="pvdoutput/pvdoutput_0_26.pvtu"/>
    <DataSet timestep="0.00269998" part="0" file="pvdoutput/pvdoutput_0_27.pvtu"/>
    <DataSet timestep="0.0028" part="0" file="pvdoutput/pvdoutput_0_28.pvtu"/>
    <DataSet timestep="0.00289991" part="0" file="pvdoutput/pvdoutput_0_29.pvtu"/>
    <DataSet timestep="0.00300002" part="0" file="pvdoutput/pvdoutput_0_30.pvtu"/>
    <DataSet timestep="0.00309998" part="0" file="pvdoutput/pvdoutput_0_31.pvtu"/>
    <DataSet timestep="0.00319999" part="0" file="pvdoutput/pvdoutput_0_32.pvtu"/>
    <DataSet timestep="0.00329994" part="0" file="pvdoutput/pvdoutput_0_33.pvtu"/>
    <DataSet timestep="0.00340002" part="0" file="pvdoutput/pvdoutput_0_34.pvtu"/>
    <DataSet timestep="0.00349997" part="0" file="pvdoutput/pvdoutput_0_35.pvtu"/>
    <DataSet timestep="0.00359999" part="0" file="pvdoutput/pvdoutput_0_36.pvtu"/>
    <DataSet timestep="0.00369996" part="0" file="pvdoutput/pvdoutput_0_37.pvtu"/>
    <DataSet timestep="0.00379999" part="0" file="pvdoutput/pvdoutput_0_38.pvtu"/>
    <DataSet timestep="0.00389998" part="0" file="pvdoutput/pvdoutput_0_39.pvtu"/>
    <DataSet timestep="0.00399999" part="0" file="pvdoutput/pvdoutput_0_40.pvtu"/>
    <DataSet timestep="0.00410001" part="0" file="pvdoutput/pvdoutput_0_41.pvtu"/>
    <DataSet timestep="0.00419997" part="0" file="pvdoutput/pvdoutput_0_42.pvtu"/>
    <DataSet timestep="0.00429999" part="0" file="pvdoutput/pvdoutput_0_43.pvtu"/>
  </Collection>
</VTKFile>

```

I would suggest using ParaView to open your timeseries and then save as a pvd file.

---

<div class="post-metadata">

### Author: ![vachan-potluri](https://discourse.paraview.org/user_avatar/discourse.paraview.org/vachan-potluri/32/2919_2.png) [@vachan-potluri](https://discourse.paraview.org/u/vachan-potluri)
#### Post date: [February 3, 2020, 4:17am UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/3 "2020-02-03T04:17:22Z")

</div>

Hi Mathieu,

Thanks for the response. In my case, timestep data is written to a single separate file which only contains two columns corresponding to output counter and time. I have written a python script to read this file and generate a `.pvd` file. So if I open `*.pvtu.*` files as a set and save the data as `.pvd`, I will still be missing on the time data. Is there a way to read the timestep file along with `*.pvtu.*` file set? I would then not require the `.pvd` file.

---

<div class="post-metadata">

### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 3, 2020, 4:19am UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/4 "2020-02-03T04:19:05Z")

</div>

No, but you will be able to generate a correctly formated .pvd file and you could then add your timestep in.

---

<div class="post-metadata">

### Author: ![vachan-potluri](https://discourse.paraview.org/user_avatar/discourse.paraview.org/vachan-potluri/32/2919_2.png) [@vachan-potluri](https://discourse.paraview.org/u/vachan-potluri)
#### Post date: [February 3, 2020, 4:30am UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/5 "2020-02-03T04:30:53Z")

</div>

I made a silly mistake! I used `Dataset` with a small ‘s’ and hence paraview was ignoring all these elements. Sorry for not checking my format.

But now I have another issue. It seems like paraview is unable to ascertain the format of the files since they have an extension `.pvtu.n` rather than just `.pvtu`. These are the first two lines of the error message.

```auto
ERROR: In /home/ubuntu/OpenFOAM/ThirdParty-dev/ParaView-5.6.0/ParaViewCore/VTKExtensions/Default/vtkXMLCollectionReader.cxx, line 444
vtkPVDReader (0x560858045d20): Could not determine the data type for the first dataset. Please make sure this file format is supported.

```

In the `DataSet` element, is there a way to specify explicitly that this file is a `.pvtu` file? How can I resolve this?

Thanks for the quick response and sorry for my negligence in previous post.

---

<div class="post-metadata">

### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [February 3, 2020, 4:34am UTC](https://discourse.paraview.org/t/pvd-collection-of-pvtu-files-gives-blank-output/3483/6 "2020-02-03T04:34:51Z")

</div>

`filename.pvtu.n` is not a valid file format.

use this numbering instead.  
`filename_n.pvtu`