[vtkusers] Marching Cubes Problem

[Vinícius da Silva]

Hello, everybody.

I'm testing VTK marching cubes to know if this algorithm suits my needs. I'm
trying to make a simple example, using the vtkMarchingCubes in a
vtkImageData volumetric array, but the resulting vtkPolyData doesn't make
much sense for me. Am I doing something wrong? The code is below.

Thanks.

void calcIsoSurface(vtkPolyData *pPolyData){
    //create an image data
    vtkSmartPointer<vtkImageData> pImageData =
vtkSmartPointer<vtkImageData>::New();

    //specify the size of the image data
    pImageData->SetDimensions(I_XDIM , I_YDIM , I_ZDIM);
    pImageData->SetNumberOfScalarComponents(1);
    pImageData->SetScalarTypeToDouble();

    int* piDims = pImageData->GetDimensions();

    cout << "Dims: " << " x: " << piDims[0] << " y: " << piDims[1] << " z: "
<< piDims[2] << endl;
    cout << "Number of points: " << pImageData->GetNumberOfPoints() << endl;
    cout << "Number of cells: " << pImageData->GetNumberOfCells() << endl;

    for (int iZ = 0; iZ < piDims[2]; iZ++){
        for (int iY = 0; iY < piDims[1]; iY++){
            for (int iX = 0; iX < piDims[0]; iX++){
                double* pdPixel =
static_cast<double*>(pImageData->GetScalarPointer(iX , iY , iZ));
                if(iX < 1 || iY < 1 || iZ < 1 || iX > piDims[0] - 2 || iY >
piDims[1] - 2 || iZ > piDims[2] - 2){
                    pdPixel[0] = 10.0;
                }else if(iX < 2 || iY < 2 || iZ < 2 || iX > piDims[0] - 3 ||
iY > piDims[1] - 3 || iZ > piDims[2] - 3){
                    pdPixel[0] = 0.0;
                }
                else{
                    pdPixel[0] = -10.0;
                }
            }
        }
    }

    pImageData->Update();
    vtkMarchingCubes *pIso = vtkMarchingCubes::New();
    pIso->SetInput(pImageData);
    pIso->SetNumberOfContours(1);
    pIso->SetValue(0, 0.0);
    pIso->Update();

    vtkIndent indent;
    pIso->PrintSelf(cout , indent);
    g_pPolyData = vtkPolyData::New();
    g_pPolyData = pIso->GetOutput();
    g_pPolyData->Update();

    //writing the status of PolyData
    cout << endl << "isoSurface: lines: " << g_pPolyData->GetNumberOfLines()
<< " vertices: " << g_pPolyData->GetNumberOfVerts() << endl;
}

Best Regards,

Vinícius da Silva,
M. Sc. Student
Systems Engineering and Computation Program
PESC/COPPE/UFRJ
Rio de Janeiro - Brazil
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