[vtkusers] Marching Cubes Problem

[David Doria]

2010/7/22 Vinícius da Silva <dsilva.vinicius at gmail.com>:
> 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
>

Have you seen the wiki examples? http://www.vtk.org/Wiki/VTK/Examples

There is an example of marching cubes there:
http://www.vtk.org/Wiki/VTK/Examples/Medical/GenerateModelsFromLabels

Let us know if you still have any problems.

Thanks,

David