[vtkusers] QuadraticHexahedra

[James C. Robinson]

Dear All,

Before I begin - I don't have simple example code to demonstrate the
problem, but I still cannot implement the vtkQuadraticHexahedra properly. (I
am using v4.2.). I have my code set up for multiple builds, so I can choose
which version to compile with, as well as which element (cell)
representation to use in VTK. When I use the linear hexahedra, both the
vtkCutter probe and the vtkStreamTracer are behaving well. However, when I
change to vtkQuadraticHexahedra, neither work - that is, the cut surface is
not there and the streamtube (which is based on the vtkStreamTracer) is not
there either.

Here are some simple snippets:
  vtkUnstructuredGridReader *pMeshReader ;
  vtkUnstructuredGrid       *pUnstructuredGrid ;
  vtkGeometryFilter         *pGeometry ;

  vtkPlane          *pPlane ;
  CPlane            *pCutPlane ;
protected:
  vtkCutter         *pCrossSection ;
  vtkClipPolyData   *pXSectionClipper ;
  vtkAppendPolyData *pCutMeshData ;
  vtkPolyDataMapper *pXSectionPressureMapper;
  vtkActor          *pCrossSectionPressureActor ;
  vtkPolyDataMapper *pXSectionMaterialMapper;
  vtkActor          *pCrossSectionMaterialActor ;
  vtkFeatureEdges   *pCutWireFrame ;
  vtkPolyDataMapper *pCutWireFrameMapper;
  vtkActor          *pCutEdgeActor;

// A plane and cross section
  pMeshReader   = vtkUnstructuredGridReader::New();
   pGeometry     = vtkGeometryFilter::New() ;
// The file is linked to the vtkUnstructuredGridReader in here
  pUnstructuredGrid = pMeshReader->GetOutput() ;
   pGeometry->SetInput(pUnstructuredGrid) ;


  pPlane = vtkPlane::New() ;
  pCrossSection = vtkCutter::New() ;
  pXSectionClipper = vtkClipPolyData::New() ;
  pCutMeshData = vtkAppendPolyData::New() ;

  pXSectionPressureMapper = vtkPolyDataMapper::New() ;
  pXSectionMaterialMapper = vtkPolyDataMapper::New() ;
  pCrossSectionPressureActor = vtkActor::New();
  pCrossSectionMaterialActor = vtkActor::New();
  pCrossSectionPressureActor->VisibilityOff();
  pCrossSectionMaterialActor->VisibilityOff();

  pCutWireFrame = vtkFeatureEdges::New() ;
  pCutWireFrameMapper = vtkPolyDataMapper::New() ;
  pCutEdgeActor = vtkActor::New();
  pCutEdgeActor->VisibilityOff();

  pCutPlane = new CPlane() ;  // My own class
  pMyFlowPlane = new CPlane() ;

// The plane used to cut the mesh
    pPlane->SetOrigin(0.0,0.0,0.0) ; // Mid point of the wellbore
    
   pPlane->SetNormal(0.0,1.0,0.0) ;

// The actual plane surface
    pCrossSection->SetInput(pMeshReader->GetOutput()) ;
	pCrossSection->SetCutFunction(pPlane) ;

// What is left after the cut is made
    pXSectionClipper->SetInput(pGeometry->GetOutput()) ;
	pXSectionClipper->SetClipFunction(pPlane) ;

    pCutMeshData->AddInput(pXSectionClipper->GetOutput()) ;
    pCutMeshData->AddInput(pCrossSection->GetOutput()) ;


    if (CreateLookUpTable) pXSectionPressureMapper->SetLookupTable(pLut) ;
	pXSectionPressureMapper->SetInput(pCutMeshData->GetOutput()) ;

    if (CreateLookUpTable) pXSectionMaterialMapper->SetLookupTable(pMatLut)
;
	pXSectionMaterialMapper->SetInput(pCutMeshData->GetOutput()) ;
	pXSectionMaterialMapper->SetScalarModeToUseCellData() ;

    pCrossSectionPressureActor->SetMapper(pXSectionPressureMapper);
    pCrossSectionMaterialActor->SetMapper(pXSectionMaterialMapper);

    pCutWireFrame->SetInput(pCutMeshData->GetOutput()) ;
    pCutWireFrame->ManifoldEdgesOn() ;
	pCutWireFrameMapper->SetInput(pCutWireFrame->GetOutput()) ;
	pCutWireFrameMapper->ScalarVisibilityOff() ;

    pCutEdgeActor->SetMapper(pCutWireFrameMapper);
    (pCutEdgeActor->GetProperty())->SetColor(0.0,0.0,0.0) ;

I give up... trying to extract the pertinent bits is a little arduous.
Instead, think of it this way... Have any of you successfully used vtkCutter
to slice through a quadhex mesh? If yes, have you examples of code.
Similarly on examples of vtkStreamTracer with quad hexes.

Many thanks,

Jim
______________________

James C. Robinson, PhD,
Chartered Engineer,
Kepler Simulation Systems Ltd.,
42 Rivergrove, 
Glanmire, Co. Cork,
Eire

Tel:         +353-21-4822028
Tel:         +353-87-2393010
Fax:        +353-21-4822028
E-mail:     j.robinson at kepler-systems.com
______________________

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