[vtkusers] Cut slices out of polydata

[Marc Huber]

Hi,

I wanted to cut a polydata object in several slices

When I apply this example it works all fine:
http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataContourToImageData

But I have a polydata object and no sphere and I want to produce a *.jpg 
file.
My result is just a black image and I'm wondering what the problem might be.
Has anyone an idea?

Here is my code (Original code commented out and mine in red):

//ORIGINAL CODE
     //vtkSmartPointer<vtkSphereSource> sphereSource = 
vtkSmartPointer<vtkSphereSource>::New();
     //    sphereSource->SetPhiResolution(30);
     //    sphereSource->SetThetaResolution(30);
     //    sphereSource->SetCenter(40, 40, 0);
     //    sphereSource->SetRadius(20);

     //MY CODE
     vtkSmartPointer<vtkPolyData> polydata = 
vtkSmartPointer<vtkPolyData>::New();
polydata->ShallowCopy(stlActor->GetMapper()->GetInputAsDataSet());

     vtkSmartPointer<vtkCutter> circleCutter = 
vtkSmartPointer<vtkCutter>::New();
//circleCutter->SetInputConnection(sphereSource->GetOutputPort()); 
//ORIGINAL
circleCutter->SetInputConnection(polydata->GetProducerPort()); //MY CODE
     vtkSmartPointer<vtkPlane> cutPlane = vtkSmartPointer<vtkPlane>::New();
//cutPlane->SetOrigin(sphereSource->GetCenter()); //ORIGINAL
cutPlane->SetOrigin(polydata->GetCenter()); //MY CODE
         cutPlane->SetNormal(0, 0, 1);
     circleCutter->SetCutFunction(cutPlane);
     vtkSmartPointer<vtkStripper> stripper = 
vtkSmartPointer<vtkStripper>::New();
stripper->SetInputConnection(circleCutter->GetOutputPort()); // valid circle
         stripper->Update();
     // that's our circle
     vtkSmartPointer<vtkPolyData> circle = stripper->GetOutput();

     // write circle out
     vtkSmartPointer<vtkXMLPolyDataWriter> polyDataWriter = 
vtkSmartPointer<vtkXMLPolyDataWriter>::New();
         polyDataWriter->SetInput(circle);
         polyDataWriter->SetFileName("circle.vtp");
         polyDataWriter->SetCompressorTypeToNone();
         polyDataWriter->SetDataModeToAscii();
         polyDataWriter->Write();

     // prepare the binary image's voxel grid
     double bounds[6];
     circle->GetBounds(bounds);
     double spacing[3]; // desired volume spacing
     spacing[0] = 0.5;
     spacing[1] = 0.5;
     spacing[2] = 0.5;
     vtkSmartPointer<vtkImageData> whiteImage = 
vtkSmartPointer<vtkImageData>::New();
         whiteImage->SetSpacing(spacing);

     // compute dimensions
     int dim[3];
     for (int i = 0; i < 3; i++)
     {
         dim[i] = static_cast<int>(ceil((bounds[i * 2 + 1] - bounds[i * 
2]) /spacing[i])) + 1;
         if (dim[i] < 1){ dim[i] = 1;}
     }
     whiteImage->SetDimensions(dim);
     whiteImage->SetExtent(0, dim[0] - 1, 0, dim[1] - 1, 0, dim[2] - 1);
     double origin[3];
     // NOTE: I am not sure whether or not we had to add some offset!
     origin[0] = bounds[0];// + spacing[0] / 2;
     origin[1] = bounds[2];// + spacing[1] / 2;
     origin[2] = bounds[4];// + spacing[2] / 2;
     whiteImage->SetOrigin(origin);
     whiteImage->SetScalarTypeToUnsignedChar();
     whiteImage->AllocateScalars();
     // fill the image with foreground voxels:
     unsigned char inval = 255;
     unsigned char outval = 0;
     vtkIdType count = whiteImage->GetNumberOfPoints();
     for (vtkIdType i = 0; i < count; ++i)
     {
whiteImage->GetPointData()->GetScalars()->SetTuple1(i, inval);
     }

     // sweep polygonal data (this is the important thing with contours!)
     vtkSmartPointer<vtkLinearExtrusionFilter> extruder =
         vtkSmartPointer<vtkLinearExtrusionFilter>::New();
         extruder->SetInput(circle);
         extruder->SetScaleFactor(1.);
         extruder->SetExtrusionTypeToNormalExtrusion();
         extruder->SetVector(0, 0, 1);
         extruder->Update();

     // polygonal data --> image stencil:
     vtkSmartPointer<vtkPolyDataToImageStencil> pol2stenc = 
vtkSmartPointer<vtkPolyDataToImageStencil>::New();
         pol2stenc->SetTolerance(0); // important if 
extruder->SetVector(0, 0, 1) !!!
pol2stenc->SetInputConnection(extruder->GetOutputPort());
         pol2stenc->SetOutputOrigin(origin);
         pol2stenc->SetOutputSpacing(spacing);
pol2stenc->SetOutputWholeExtent(whiteImage->GetExtent());
         pol2stenc->Update();

     // cut the corresponding white image and set the background:
     vtkSmartPointer<vtkImageStencil> imgstenc = 
vtkSmartPointer<vtkImageStencil>::New();
         imgstenc->SetInput(whiteImage);
         imgstenc->SetStencil(pol2stenc->GetOutput());
         imgstenc->ReverseStencilOff();
         imgstenc->SetBackgroundValue(outval);
         imgstenc->Update();

     //ORIGINAL CODE
     //vtkSmartPointer<vtkMetaImageWriter> imageWriter =
     //  vtkSmartPointer<vtkMetaImageWriter>::New();
     //imageWriter->SetFileName("labelImage.mhd");
//imageWriter->SetInputConnection(imgstenc->GetOutputPort());
     //imageWriter->Write();

     //MY CODE
       vtkSmartPointer<vtkJPEGWriter> cutWriter = 
vtkSmartPointer<vtkJPEGWriter>::New();
         cutWriter->SetFileName("cut1.jpg");
cutWriter->SetInputConnection(imgstenc->GetOutputPort());
         cutWriter->Write();

-- 
Best regards / Mit freundlichen Grüßen
Marc Huber

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