[vtkusers] avoiding/removing non-manifold parts from the result of vtkMarchingCubes

[Dr. Roman Grothausmann]

On 02/08/13 16:06, Bill Lorensen wrote:
> Marching Cubes should not generate non-manifold surfaces. The offending triangle
> looks suspicious. What does the rest of your pipeline look like?

Thanks Bill for looking into this. I get the very same output using paraview and 
its contour filter when ticking "Generate Triangles" or using vmtkmarchingcubes 
(which seems to use only vtkMarchingCubes in vmtkmarchingcubes.py). To check it 
trice I used the simple program below and got the same output again. Only 
paraview and its contour filter without ticking "Generate Triangles" yields a 
different result.

_____________________________

#include <vtkSmartPointer.h>
#include <vtkMetaImageReader.h>
//#include <vtkImageConstantPad.h>
#include <vtkMarchingCubes.h>
#include <vtkXMLPolyDataWriter.h>//for vtp-files

#include <vtkCallbackCommand.h>
#include <vtkCommand.h>


void ProgressFunction ( vtkObject* caller, long unsigned int eventId, void* 
clientData, void* callData )
      {

      vtkAlgorithm *d= static_cast<vtkAlgorithm*>(caller);
      fprintf(stderr, "\rFilter progress: %5.1f%%", 100.0 * d->GetProgress());
      std::cerr.flush();

      }

int main(int argc, char* argv[]){
      if( argc != 5 )
	{
	std::cerr << "Usage: " << argv[0];
	std::cerr << " inputImage";
	std::cerr << " outputMesh";
	std::cerr << " level normals";
	std::cerr << std::endl;
	return EXIT_FAILURE;
	}

      if(!(strcasestr(argv[1],".mhd"))) {
	std::cout << "The input should end with .mhd" << std::endl;
	return -1;
	}

      if(!(strcasestr(argv[2],".vtp"))) {
	std::cout << "The input should end with .vtp" << std::endl;
	return -1;
	}

      vtkSmartPointer<vtkCallbackCommand> progressCallback = 
vtkSmartPointer<vtkCallbackCommand>::New();
      progressCallback->SetCallback(ProgressFunction);

      vtkSmartPointer<vtkMetaImageReader> reader =
          vtkSmartPointer<vtkMetaImageReader>::New();

      reader->SetFileName(argv[1]);
      reader->Update();

      vtkSmartPointer<vtkMarchingCubes> mc= 
vtkSmartPointer<vtkMarchingCubes>::New();

      mc->SetInputConnection(reader->GetOutputPort());
      mc->SetValue(0, atof(argv[3]));
      //mc->ComputeNormalsOn();
      mc->SetComputeNormals(atoi(argv[4]));
      //mc->ComputeGradientsOn();
      //mc->ComputeScalarsOn();
      std::cout << "Executing discrete marching cubes..." << std::endl;
      mc->AddObserver(vtkCommand::ProgressEvent, progressCallback);
      mc->Update();
      std::cout  << std::endl << "done." << std::endl;

      vtkSmartPointer<vtkXMLPolyDataWriter> Pwriter = 
vtkSmartPointer<vtkXMLPolyDataWriter>::New();
      Pwriter->SetFileName(argv[2]);
      Pwriter->SetInputConnection(mc->GetOutputPort());

      Pwriter->Update();

      return EXIT_SUCCESS;
      }


>
>
>
> On Fri, Aug 2, 2013 at 8:23 AM, Dr. Roman Grothausmann
> <grothausmann.roman at mh-hannover.de <mailto:grothausmann.roman at mh-hannover.de>>
> wrote:
>
>     Dear mailing list members,
>
>
>     Recently, I came across a voxel-dataset that when meshed with
>     vtkMarchingCubes results in a mesh that contains non-manifold edges (magenta
>     line in attached image).
>     How can this be avoided?
>     Using paraview's contour filter and switching off "Generate Triangles"
>     creates a slightly different surface mesh that does not contain non-manifold
>     edges. However vtkMarchingCubes does not seem to have any option concerning
>     triangulation.
>     What filter/option do I have to use to get the same result just with pure VTK?
>
>     As a workaround: Is it possible to split the mesh at non-manifold edges?
>     vtkIntersectionPolyDataFilter sounds promising but seems to need surfaces
>     not just the edges.
>
>     Any help or hints are very much appreciated
>     Roman
>
>
>
> --
> Unpaid intern in BillsBasement at noware dot com

-- 
Dr. Roman Grothausmann

Tomographie und Digitale Bildverarbeitung
Tomography and Digital Image Analysis

Institut für Funktionelle und Angewandte Anatomie, OE 4120
Medizinische Hochschule Hannover
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D-30625 Hannover

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