# VtkPolyData clip

**URL:** https://discourse.vtk.org/t/vtkpolydata-clip/7006
**Category:** Support
**Created:** [October 28, 2021, 7:04pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006 "2021-10-28T19:04:04Z")
**Posts on this page:** 6
**Page:** 1

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### Author: ![Hanxin\_Hua](https://discourse.vtk.org/user_avatar/discourse.vtk.org/hanxin_hua/32/3787_2.png) [@Hanxin\_Hua](https://discourse.vtk.org/u/Hanxin_Hua)
#### Post date: [October 28, 2021, 7:04pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/1 "2021-10-28T19:04:04Z")

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Hi everyone,  
 ![1635447638(1)](https://discourse.vtk.org/uploads/default/original/2X/6/68557ce711b93eec04882a522258bd1ac24afc10.jpeg)  
I have a problem. So in the image, the white part is a polydata of an iso surface. And I defined the implicit function of a sphere and cut it.

```
    vtkNew<vtkClipPolyData> isoClip;
skinClip->SetInputData(m_IsoSurfacePolyData);
skinClip->SetClipFunction(sphere);
skinClip->SetValue(0);
skinClip->GenerateClipScalarsOn();
skinClip->Update();

```

And it worked well, the sphere is cut from the iso surface.  
But I don’t want it to be hollow. Can I add the interaction part’s surface.  
I used vtlProbeFilter, but it did not work right.

Thank you!

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<div class="post-metadata">

### Author: ![Charles\_Gueunet](https://discourse.vtk.org/user_avatar/discourse.vtk.org/charles_gueunet/32/239_2.png) [@Charles\_Gueunet](https://discourse.vtk.org/u/Charles_Gueunet)
#### Post date: [October 29, 2021, 8:00am UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/2 "2021-10-29T08:00:34Z")

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The isosurface of a scalar field in a 3D mesh is expected to be a surface, and not necessarily a watershed one. If you want to extract region with a scalar value above a given threshold, you may use the threshold filter. This way, you will have a dense result.

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<div class="post-metadata">

### Author: ![Hanxin\_Hua](https://discourse.vtk.org/user_avatar/discourse.vtk.org/hanxin_hua/32/3787_2.png) [@Hanxin\_Hua](https://discourse.vtk.org/u/Hanxin_Hua)
#### Post date: [October 29, 2021, 2:37pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/4 "2021-10-29T14:37:12Z")

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Thank you for the reply.  
What I really want is something like this [https://kitware.github.io/vtk-examples/site/Cxx/Medical/TissueLens/#description](https://kitware.github.io/vtk-examples/site/Cxx/Medical/TissueLens/#description)  
But apparently this is not working

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<div class="post-metadata">

### Author: ![Charles\_Gueunet](https://discourse.vtk.org/user_avatar/discourse.vtk.org/charles_gueunet/32/239_2.png) [@Charles\_Gueunet](https://discourse.vtk.org/u/Charles_Gueunet)
#### Post date: [October 29, 2021, 2:41pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/5 "2021-10-29T14:41:24Z")

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Can you also show how you use the probe filter ?  
In the given example there are these lines to create the sphere with the right geometry, probe the values and cut it to match the whole.

```auto
  // Define a model for the "lens". Its geometry matches the implicit
  // sphere used to clip the isosurface
  vtkNew<vtkSphereSource> lensModel;
  lensModel->SetRadius(50);
  lensModel->SetCenter(73, 52, 15);
  lensModel->SetPhiResolution(201);
  lensModel->SetThetaResolution(101);

  // Sample the input volume with the lens model geometry
  vtkNew<vtkProbeFilter> lensProbe;
  lensProbe->SetInputConnection(lensModel->GetOutputPort());
  lensProbe->SetSourceConnection(reader->GetOutputPort());

  // Clip the lens data with the isosurface value
  vtkNew<vtkClipDataSet> lensClip;
  lensClip->SetInputConnection(lensProbe->GetOutputPort());
  lensClip->SetValue(500);
  lensClip->GenerateClipScalarsOff();
  lensClip->Update();

```

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<div class="post-metadata">

### Author: ![Hanxin\_Hua](https://discourse.vtk.org/user_avatar/discourse.vtk.org/hanxin_hua/32/3787_2.png) [@Hanxin\_Hua](https://discourse.vtk.org/u/Hanxin_Hua)
#### Post date: [October 29, 2021, 2:57pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/6 "2021-10-29T14:57:57Z")

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Here it is  
m\_IsoSurfaceMapperBR has the input of the iso surface  
m\_BoneReductionImageBR is the imagedata used to generate the iso surface

```
vtkSmartPointer<vtkSphere> sphere = vtkSmartPointer<vtkSphere>::New();
vtkSmartPointer<vtkSphereSource> spherePoly = vtkSmartPointer<vtkSphereSource>::New();
double tip[3];
m_drillModel->GetDrillTip(tip);
sphere->SetCenter(tip);
sphere->SetRadius(6.0);
spherePoly->SetCenter(tip);
spherePoly->SetRadius(6.0);
spherePoly->SetPhiResolution(200);
spherePoly->SetThetaResolution(200);

vtkNew<vtkClipPolyData> isoClip;
skinClip->SetInputData(m_IsoSurfaceMapperBR->GetInput());
skinClip->SetClipFunction(sphere);
skinClip->SetValue(0);
skinClip->GenerateClipScalarsOn();
skinClip->Update();

vtkNew<vtkProbeFilter> probe;
probe->SetInputData(spherePoly);
probe->SetSourceData(m_BoneReductionImageBR);
probe->Update();

vtkNew<vtkClipPolyData> probeClip;
probeClip->SetInputConnection(probe->GetOutputPort());
probeClip->SetValue(30);
probeClip->GenerateClipScalarsOff();
probeClip->Update();

vtkSmartPointer<vtkAppendPolyData> appendData = vtkSmartPointer<vtkAppendPolyData>::New();
appendData->AddInputData(isoClip->GetOutPut());
appendData->AddInputData(probeClip->GetOutPut());
appendData->Update();
vtkSmartPointer<vtkCleanPolyData> clean = vtkSmartPointer<vtkCleanPolyData>::New();
clean->SetInputData(appendData->GetOutput());
clean->Update();

m_IsoSurfaceMapperBR->SetInputData(clean->GetOutput());
m_IsoSurfaceMapperBR->ScalarVisibilityOff();
m_IsoSurfaceMapperBR->Update();
```

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<div class="post-metadata">

### Author: ![Hanxin\_Hua](https://discourse.vtk.org/user_avatar/discourse.vtk.org/hanxin_hua/32/3787_2.png) [@Hanxin\_Hua](https://discourse.vtk.org/u/Hanxin_Hua)
#### Post date: [October 29, 2021, 3:04pm UTC](https://discourse.vtk.org/t/vtkpolydata-clip/7006/7 "2021-10-29T15:04:58Z")

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I append the two polydata to a single one and use the same mapper for that