[vtkusers] Using vtkImplicitDataSet to clip data

[Roger Mason]

Hello,

I'm trying to use a vtkImplicitDataSet to apply an arbitrary surface as
a clipping function.  A minimal version of the code is given below:

[ -- read in data from file -- ]

  vtkSmartPointer<vtkPlane> plane 
    = vtkSmartPointer<vtkPlane>::New();
  plane->SetOrigin(0,0,0);
  plane->SetNormal(0,0,1);

  vtkSmartPointer<vtkImplicitSum> sum 
    = vtkSmartPointer<vtkImplicitSum>::New();
  sum->AddFunction(plane);

  vtkSmartPointer<vtkSampleFunction> sample
    = vtkSmartPointer<vtkSampleFunction>::New();
  sample->SetImplicitFunction(sum);
  sample->SetSampleDimensions(10, 10, 20);

  vtkSmartPointer<vtkContourFilter> surface
    = vtkSmartPointer<vtkContourFilter>::New();
  surface->SetInputConnection(sample->GetOutputPort());
  surface->SetValue(0, 0.0);

  vtkSmartPointer<vtkImplicitDataSet> cutfunction
    = vtkSmartPointer<vtkImplicitDataSet>::New();
  cutfunction->SetDataSet(surface->GetOutput());

  // Clip on the cut surface
  vtkSmartPointer<vtkClipPolyData> clipper =
    vtkSmartPointer<vtkClipPolyData>::New();
  clipper->SetInput(polyData);
  clipper->SetClipFunction(cutfunction);
  clipper->GenerateClipScalarsOn();
  clipper->GenerateClippedOutputOn();
  clipper->InsideOutOn();
  clipper->Update();
  polyData = clipper->GetClippedOutput();

  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInput(polyData);

  vtkSmartPointer<vtkActor> actor
    = vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);

  // Graphics
  vtkSmartPointer<vtkRenderer> ren =
    vtkSmartPointer<vtkRenderer>::New();
  ren->SetBackground(.1, .2, .3);
 
  vtkSmartPointer<vtkRenderWindow> renWin =
    vtkSmartPointer<vtkRenderWindow>::New();
  renWin->AddRenderer(ren);
  renWin->SetSize(512,512);
 
  vtkSmartPointer<vtkRenderWindowInteractor> iren =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  iren->SetRenderWindow(renWin);

  actor->GetProperty()->SetColor(1,0,0);
  actor->GetProperty()->SetInterpolationToFlat();
  ren->AddActor(actor);

  ren->ResetCamera();
  iren->Initialize();
  iren->Start();

The program compiles and runs and I have verified that the input data
are read correctly and the clipping surface is generated.  However, the
results obtained with GetClippedOutput() are not displayed.  I have
inserted a writer to write the clipped data as ascii to a file.  On
opening the file in a test program I see the error:

"Generic Warning: In /home/rmason/Software/VTK/IO/vtkDataReader.cxx, line 1383
Error reading ascii data. Possible mismatch of datasize with
declaration."

If anyone can suggest how to debug this further, I'd appreciate the
help.

Thanks,
Roger