# Exposing VTK filter through plugin fails
**URL:** https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248
**Category:** ParaView Support
**Created:** [May 18, 2021, 8:35pm UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248 "2021-05-18T20:35:26Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@bbellster](https://discourse.paraview.org/u/bbellster)
#### Post date: [May 18, 2021, 8:35pm UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/1 "2021-05-18T20:35:26Z")
Hi, new paraview user here. In searching for a way to uncover existing VTK filters I found this page:
[https://kitware.github.io/paraview-docs/latest/cxx/PluginHowto.html](https://kitware.github.io/paraview-docs/latest/cxx/PluginHowto.html)
I tried following the example with multiple inputs - vtkLandmarkRegistrationFilter which is perfect because this is actually one of the filters I’d like to use. The problem is that this causes the application to crash.
Steps:
1. copy the xml from the webpage and save as .xml
2. Tools-\>Manage Pulgins-\> Load New → file I just saved
3. So far so good
4. type lmReg = LandmarkTransformFilter() into shell , hit enter and it crashes
Help troubleshooting this is much appreciated.
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### Author:  [@ben.boeckel](https://discourse.paraview.org/u/ben.boeckel)
#### Post date: [May 19, 2021, 1:48am UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/2 "2021-05-19T01:48:12Z")
Hmm. It looks like that class never existed (at least in the VTK repository). I wonder if it is missing some references from elsewhere. The `vtkLandmarkTransform` class is missing a `SourceDataSet` though, so it’s not quite that easy.
That said, crashing is also not good.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 19, 2021, 8:23am UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/3 "2021-05-19T08:23:40Z")
`vtkLandmarkRegistrationFilter` does not exist in google.
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### Author:  [@bbellster](https://discourse.paraview.org/u/bbellster)
#### Post date: [May 19, 2021, 12:32pm UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/4 "2021-05-19T12:32:00Z")
I should have mentioned that I changed the class as follows:
class=“vtkLandmarkTransform”
Looking at the error logs, I see:
( 50.101s) [paraview]vtkPVAlgorithmPortsInfo:55 ERR| . vtkPVAlgorithmPortsInformation (0000023256E3C580): Could not downcast vtkAlgorithm.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 19, 2021, 12:45pm UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/5 "2021-05-19T12:45:53Z")
> [@bbellster](#):
>
> vtkLandmarkTransform
This is not a filter (a vtkAlgorithm). You can’t use it as if it was one.
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### Author:  [@bbellster](https://discourse.paraview.org/u/bbellster)
#### Post date: [May 19, 2021, 12:49pm UTC](https://discourse.paraview.org/t/exposing-vtk-filter-through-plugin-fails/7248/6 "2021-05-19T12:49:07Z")
That would make sense. Thanks