[vtkusers] Another vtkMarchingCubes question

[Luca Pamparana]

Hello everyone,

I have a question about vtkDiscreteMarchingCubes object.

What I am doing is as follows:

- Load an input 3D volume (a binary mask).
- Apply the vtkDiscreteMarchingCubes filter.
- Cut through the resulting dataset using a vtkCutter.
- Use a vtkStripper to generate closed loop polygons
- Visualize these polygons.

The problem is that the tip of my input dataset is missing. The structures
at the tip are quite small and I am guessing that not enough triangles are
being generated and it is clipping my dataset somehow. I was wondering if
someone has had the same problem and would know how to avoid this.

My code looks more or less as follows:

void ExtractBinaryMask(vtkImageData * in)
{
    if (in)
    {
        // Pass this to the marching cube filter
        discreteMarchingCubes->ComputeNormalsOff();
        discreteMarchingCubes>ComputeGradientsOff();
        discreteMarchingCubes->SetInput(in);

          // Get the scalar range
          double * range = in->GetScalarRange();
          // We set the contour surface value to the greatest value
          discreteMarchingCubes->SetValue(0, range[1]);

          vtkPlane * plane = vtkPlane::New();
          vtkCutter * cutter = vtkCutter::New();
          vtkStripper * stripper = vtkStripper::New();

          plane->SetOrigin(in->GetOrigin());
          plane->SetNormal(0, 0, 1);

          cutter->SetInput(discreteMarchingCubes->GetOutput());
          cutter->SetCutFunction(plane);
          cutter->Update();

          stripper->SetInput(cutter->GetOutput());
          stripper->Update();

          // poly is vtkPolyData
          poly->SetPoints(stripper->GetOutput()->GetPoints());
          poly->SetPolys(stripper->GetOutput()->GetLines());

          // we have the points now
    }
}


I shift the plane along the length of the whole volume and do this
extraction for the whole set. However, the top tip does not return any
polygons :(

Any help would be greatly appreciated!

Thanks,
Luca
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