# Help in creating a simple filter using vtkQuadricDecimation()

**URL:** https://discourse.paraview.org/t/help-in-creating-a-simple-filter-using-vtkquadricdecimation/4378
**Category:** ParaView Support
**Created:** [May 20, 2020, 10:12pm UTC](https://discourse.paraview.org/t/help-in-creating-a-simple-filter-using-vtkquadricdecimation/4378 "2020-05-20T22:12:22Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![yw5aj](https://discourse.paraview.org/user_avatar/discourse.paraview.org/yw5aj/32/60_2.png) [@yw5aj](https://discourse.paraview.org/u/yw5aj)
#### Post date: [May 20, 2020, 10:12pm UTC](https://discourse.paraview.org/t/help-in-creating-a-simple-filter-using-vtkquadricdecimation/4378/1 "2020-05-20T22:12:22Z")

</div>

Hi all,

I tried to follow the guide and create a simple filter using vtkQuadricDecimation. However, I keep getting the paraview crashing and could not figure out why (I did select an input before applying this filter). Could anyone please help?

```
from vtkmodules.vtkCommonDataModel import vtkDataSet
from vtkmodules.util.vtkAlgorithm import VTKPythonAlgorithmBase
from vtkmodules.numpy_interface import dataset_adapter as dsa
import vtkmodules

from paraview.util.vtkAlgorithm import smproxy, smproperty, smdomain

@smproxy.filter(label="Quadratic Decimation Filter")
@smproperty.input(name="PolyDataInput", port_index=0)
@smdomain.datatype(dataTypes=["vtkPolyData"])
class QuadricDecimationFilter(VTKPythonAlgorithmBase):

    def __init__ (self):
        VTKPythonAlgorithmBase. __init__ (self, nInputPorts=1)
        self._realAlgorithm = vtk.vtkQuadricDecimation()
        
    def RequestData(self, request, inInfo, outInfo):
        self.Update()

        from vtkmodules.vtkCommonDataModel import vtkPolyData
        mesh = vtkPolyData.GetData(inInfo[0])

        self._realAlgorithm.SetInputData(mesh)
        self._realAlgorithm.VolumePreservationOn()
        self._realAlgorithm.Update()

        output = vtkPolyData.GetData(outInfo, 0)
        output.ShallowCopy(self._realAlgorithm.GetOutput())
    
    @smproperty.doublevector(name="Reduction", default_values=0.5)
    @smdomain.doublerange(min=0, max=1)    
    def SetReductionRatio(self, reduction):
        self._realAlgorithm.SetTargetReduction(reduction)
        self.Modified()

```

Thank you,  
Shawn