[vtkusers] Visualizing populated voxels

[Thommen Korah]

Hi Bill,
Thanks for the reply. I made the change as you suggested. It does something now. The resulting scene has 10-20 polygonal structures that seem to be randomly located. They definitely don't represent the data. If I replace the thresholding and geometryfilter construction with a contourfilter, everything works fine; I get a surface reconstruction of the underlying cell population generated by marching cubes. What I need now is a visualization of the actual voxels that are ON, and to convert that to a polydata. Is vtkGeometryFilter the right class for that?
Any ideas?
Thanks,Thommen

Date: Tue, 10 May 2011 19:49:13 -0400
Subject: Re: [vtkusers] Visualizing populated voxels
From: bill.lorensen at gmail.com
To: thkorah at hotmail.com
CC: vtkusers at vtk.org

Try,
vtkDataObject::FIELD_ASSOCIATION_POINTS
instead of
vtkDataObject::FIELD_ASSOCIATION_CELLS





On Tue, May 10, 2011 at 5:26 PM, Thommen Korah <thkorah at hotmail.com> wrote:






Hi,
I have a voxel grid (stored as vtkImageData). I would like to visualize the cells that are populated (greater than a particular threshold). I then want to convert the resulting surface into a polydata and write it as a PLY file. My code below that uses vtkThreshold followed by GeometryFilter doesn't work for some reason. Could anyone suggest a possible fix?

Thanks.Thommen

int VtkScene::addVoxelSurface( short* sampleGrid, double isoValue,

                              int dimX, int dimY, int dimZ,

                              double voxX, double voxY, double voxZ,

                              int minX, int minY, int minZ )

{
  
  vtkShortArray* sampleData = vtkShortArray::New();

  int numSamples = dimX * dimY * dimZ;

  sampleData->SetArray( sampleGrid, numSamples, 1 );

  sampleData->SetNumberOfComponents( 1 );

  sampleData->SetNumberOfTuples( numSamples );

  sampleData->SetName( "values" );



  // Set up sampled data space

  vtkImageData* sampledSpace = vtkImageData::New();

  sampledSpace->SetDimensions( dimX, dimY, dimZ );

  sampledSpace->SetScalarTypeToShort();

  sampledSpace->GetPointData()->SetScalars( sampleData );

  sampledSpace->SetSpacing( voxX, voxY, voxZ );  // set dimensions of a voxel

  sampledSpace->SetOrigin( (double)minX,

                           (double)minY,

                           (double)minZ );       // set lower left corner location


  vtkThreshold* threshold = vtkThreshold::New();

  threshold->SetInput(sampledSpace);

  threshold->SetInputArrayToProcess(0,0,0,vtkDataObject::FIELD_ASSOCIATION_CELLS,vtkDataSetAttributes::SCALARS);

  threshold->ThresholdBetween(5,100);

  threshold->Update();


  vtkGeometryFilter* geomFilter = vtkGeometryFilter::New();

  geomFilter->SetInput(threshold->GetOutput());

  geomFilter->Update();


  // Create mapper and actor, and add to renderer

  vtkPolyDataMapper* voxelMapper = vtkPolyDataMapper::New();

  voxelMapper->SetInput( geomFilter->GetOutput() );

  //voxelMapper->SetScalarRange(5,100);
  voxelMapper->SetScalarModeToUseCellData();

  //voxelMapper->SetColorModeToMapScalars();

  vtkActor* impGeoActor = vtkActor::New();

  impGeoActor->SetMapper( voxelMapper );

  //impGeoActor->GetProperty()->SetColor( 1.0, 0, 0 );

  //impGeoActor->GetProperty()->SetOpacity( alpha );



  int actorId = addActor( impGeoActor );



  voxelMapper->Delete();

  geomFilter->Delete();
  threshold->Delete();
  sampledSpace->Delete();
  sampleData->Delete();

  return actorId;

}
 		 	   		  

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