[vtkusers] How to use vtkCellDerivatives with unstructured grid image

[Seth Gilchrist]

Hello,
I have the unstructured grid image printed at end of this email, with two
point data sets "Dispamcement" (vectors) and "Optimizer Value" (scalors).  I
want to use vtkCellDerivatives to calculate the strain tensors from the
"Displacement" point data.  I can't figure out how to input the data into
vtkCellDerivatives.  I have tried:

vtkCellDerivatives  *dCalc = vtkCellDerivatives::New();
dCalc->SetTensorModeToComputeStrain();
dCalc->SetInput( image->GetPointData()->GetArray("Displacement") );
dCalc->Update();

and

vtkCellDerivatives  *dCalc = vtkCellDerivatives::New();
dCalc->SetTensorModeToComputeStrain();
dCalc->SetInput(image);
dCalc->SetInputArrayToProcess( [uh...I get lost here, I've tried a lot of
things]  );
dCalc->Update();

I either can't get it to compile, or the output of the filter is the same as
the input.

Can anybody point me in the right direction?

Thanks,
Seth

The cells in the image are quadratic tets.

image->Print( std::cout )...

vtkUnstructuredGrid (0x10f1150)
  Debug: Off
  Modified Time: 268
  Reference Count: 1
  Registered Events: (none)
  Source: (none)
  Information: 0x10e6130
  Data Released: False
  Global Release Data: Off
  UpdateTime: 269
  Release Data: Off
  UpdateExtent: Not Initialized
  Update Number Of Pieces: 1
  Update Piece: 0
  Update Ghost Level: 0
  MaximumNumberOfPieces: 1
  RequestExactExtent: Off
   Field Data:
    Debug: Off
    Modified Time: 252
    Reference Count: 1
    Registered Events: (none)
    Number Of Arrays: 0
    Number Of Components: 0
    Number Of Tuples: 0
  Number Of Points: 81
  Number Of Cells: 30
  Cell Data:
    Debug: Off
    Modified Time: 259
    Reference Count: 1
    Registered Events: (none)
    Number Of Arrays: 0
    Number Of Components: 0
    Number Of Tuples: 0
    Copy Tuple Flags: ( 1 1 1 1 1 0 1 )
    Interpolate Flags: ( 1 1 1 1 1 0 0 )
    Pass Through Flags: ( 1 1 1 1 1 1 1 )
    Scalars: (none)
    Vectors: (none)
    Normals: (none)
    TCoords: (none)
    Tensors: (none)
    GlobalIds: (none)
    PedigreeIds: (none)
  Point Data:
    Debug: Off
    Modified Time: 268
    Reference Count: 1
    Registered Events: (none)
    Number Of Arrays: 2
    Array 0 name = Displacement
    Array 1 name = Optimizer Value
    Number Of Components: 4
    Number Of Tuples: 81
    Copy Tuple Flags: ( 1 1 1 1 1 0 1 )
    Interpolate Flags: ( 1 1 1 1 1 0 0 )
    Pass Through Flags: ( 1 1 1 1 1 1 1 )
    Scalars: (none)
    Vectors: (none)
    Normals: (none)
    TCoords: (none)
    Tensors: (none)
    GlobalIds: (none)
    PedigreeIds: (none)
  Bounds:
    Xmin,Xmax: (57.5, 67.3)
    Ymin,Ymax: (45.7, 56.7)
    Zmin,Zmax: (41.7, 59.1)
  Compute Time: 283
  Number Of Points: 81
  Point Coordinates: 0x10e7890
  Locator: 0
  Number Of Pieces: 1
  Piece: 0
  Ghost Level: 0
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20110613/17aa3a74/attachment.htm>