# "Requires an input" error on all filter options with vtk data file (that has data)

**URL:** https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295
**Category:** ParaView Support
**Tags:** vtk
**Created:** [November 1, 2021, 12:31am UTC](https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295 "2021-11-01T00:31:11Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![Robert\_H](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/r/b9bd4f/32.png) [@Robert\_H](https://discourse.paraview.org/u/Robert_H)
#### Post date: [November 1, 2021, 12:31am UTC](https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295/1 "2021-11-01T00:31:11Z")

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Hi all,

I have a VTK dataset contaning 3D velocity from a simulation and I have just used the GUI “open” file button to load the data. I am able to represent the data using all the “surface”, “Points”, “Points Gaussian” options, however I can’t do any computations with the data.

 ![ParaviewScreenshot](https://discourse.paraview.org/uploads/default/original/2X/c/c3938ea39a29b1061234c31fe0171ffaa206c825.png)

Every filter is greyed out and if I hover over the calculator or ‘contour’ or other computed representations I get the error “Requires an input”. However there is data in the vtk, as I can see it colored in points mode.

Is there some step I’m missing or some way to force paraveiw to use the velocity data?

Best regards,  
Robert H.

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### 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: [November 2, 2021, 8:31am UTC](https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295/2 "2021-11-02T08:31:04Z")

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Press Apply

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### 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: [November 2, 2021, 8:31am UTC](https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295/3 "2021-11-02T08:31:24Z")

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> [@I've just opened my dataset. I can't add filters, and everything is greyed out](https://discourse.paraview.org/t/ive-just-opened-my-dataset-i-cant-add-filters-and-everything-is-greyed-out/4511):
>
> Make sure your dataset is selected in the Pipeline Browser Click apply (in the Properties tab) if the apply button is green

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### Author: ![Robert\_H](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/r/b9bd4f/32.png) [@Robert\_H](https://discourse.paraview.org/u/Robert_H)
#### Post date: [November 5, 2021, 6:10am UTC](https://discourse.paraview.org/t/requires-an-input-error-on-all-filter-options-with-vtk-data-file-that-has-data/8295/4 "2021-11-05T06:10:55Z")

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Wow that worked… Thank you! 😅 !