[vtk-developers] vtkAssignAttributes doesn't pass NumComponents?

[Julien Finet]

Hi all,

I'm trying to process a tensors vtkImageData by a filter that only accept
scalars.
However, I think that vtkAssignAttribute doesn't pass the number of
components in the output information.

Indeed, looking at vtkAssignAttribute::RequestInformation(), I don't see how
it could pass the "number of components". Maybe it's done later in
RequestData, but wouldn't it be too late when vtkAssignAttribute output is
connected as an input of another filter?

Here is my pipeline:

// Create Data:
  VTK_CREATE(vtkImageData,image);
  image->SetDimensions(2,1,1);

  VTK_CREATE(vtkFloatArray, tensors);
  tensors->SetName("tensors");
  tensors->SetNumberOfComponents(9);
  // 2 tuples, identity matrices
  tensors->InsertNextTuple9(1.,0.,0.,0.,1.,0.,0.,0.,1.);
  tensors->InsertNextTuple9(1.,0.,0.,0.,1.,0.,0.,0.,1.);

  image->GetPointData()->SetTensors(tensors);

// Move tensors into scalars
  VTK_CREATE(vtkAssignAttribute, assign);
  assign->Assign(vtkDataSetAttributes::TENSORS,
vtkDataSetAttributes::SCALARS, vtkAssignAttribute::POINT_DATA);
  assign->SetInput(image);

// Cast scalars
  VTK_CREATE(vtkImageCast, cast); // here I use cast but it could be any
other image filter that just process scalars
  cast->SetOutputScalarTypeToDouble();
  cast->SetInput(imageOut);
  cast->Update();

Unfortunately, the output of the cast filter is not a scalar image with 9
components but only 1.

  vtkImageData* imageOut = vtkImageData::SafeDownCast(assign->GetOutput());
  vtkImageData* imageCasted = vtkImageData::SafeDownCast(cast->GetOutput());
  if (imageCasted->GetPointData()->GetNumberOfComponents() != 9)
    {
    cerr << "Input: \n";
    image->GetPointData()->Print(cerr);
    cerr << "Intermediate: \n";
    imageOut->GetPointData()->Print(cerr);
    cerr << "Casted: \n";
    imageCasted->GetPointData()->Print(cerr);
    }

produces the output:

Input:
vtkPointData (0398BBF8)
  Debug: Off
  Modified Time: 29
  Reference Count: 1
  Registered Events: (none)
  Number Of Arrays: 1
  Array 0 name = tensors
  Number Of Components: 9
  Number Of Tuples: 2
  Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 )
  Interpolate Flags: ( 1 1 1 1 1 0 0 1 )
  Pass Through Flags: ( 1 1 1 1 1 1 1 1 )
  Scalars: (none)
  Vectors: (none)
  Normals: (none)
  TCoords: (none)
  Tensors:
    Debug: Off
    Modified Time: 26
    Reference Count: 3
    Registered Events: (none)
    Name: tensors
    Data type: float
    Size: 27
    MaxId: 17
    NumberOfComponents: 9
    Information: 00000000
    Name: tensors
    Number Of Components: 9
    Number Of Tuples: 2
    Size: 27
    MaxId: 17
    LookupTable: (none)
    Array: 0398C450
  GlobalIds: (none)
  PedigreeIds: (none)
  EdgeFlag: (none)

Intermediate:
vtkPointData (0398F5B0)
  Debug: Off
  Modified Time: 338
  Reference Count: 1
  Registered Events: (none)
  Number Of Arrays: 1
  Array 0 name = tensors
  Number Of Components: 9
  Number Of Tuples: 2
  Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 )
  Interpolate Flags: ( 1 1 1 1 1 0 0 1 )
  Pass Through Flags: ( 1 1 1 1 1 1 1 1 )
  Scalars:
    Debug: Off
    Modified Time: 26
    Reference Count: 3
    Registered Events: (none)
    Name: tensors
    Data type: float
    Size: 27
    MaxId: 17
    NumberOfComponents: 9
    Information: 00000000
    Name: tensors
    Number Of Components: 9
    Number Of Tuples: 2
    Size: 27
    MaxId: 17
    LookupTable: (none)
    Array: 0398C450
  Vectors: (none)
  Normals: (none)
  TCoords: (none)
  Tensors:
    Debug: Off
    Modified Time: 26
    Reference Count: 3
    Registered Events: (none)
    Name: tensors
    Data type: float
    Size: 27
    MaxId: 17
    NumberOfComponents: 9
    Information: 00000000
    Name: tensors
    Number Of Components: 9
    Number Of Tuples: 2
    Size: 27
    MaxId: 17
    LookupTable: (none)
    Array: 0398C450
  GlobalIds: (none)
  PedigreeIds: (none)
  EdgeFlag: (none)

Casted:
vtkPointData (037C2A30)
  Debug: Off
  Modified Time: 394
  Reference Count: 1
  Registered Events: (none)
  Number Of Arrays: 1
  Array 0 name = tensors
  Number Of Components: 1
  Number Of Tuples: 2
  Copy Tuple Flags: ( 1 1 1 1 1 1 1 1 )
  Interpolate Flags: ( 1 1 1 1 1 1 1 1 )
  Pass Through Flags: ( 1 1 1 1 1 1 1 1 )
  Scalars:
    Debug: Off
    Modified Time: 391
    Reference Count: 1
    Registered Events: (none)
    Name: tensors
    Data type: double
    Size: 2
    MaxId: 1
    NumberOfComponents: 1
    Information: 00000000
    Name: tensors
    Number Of Components: 1
    Number Of Tuples: 2
    Size: 2
    MaxId: 1
    LookupTable: (none)
    Array: 037C6DC8
  Vectors: (none)
  Normals: (none)
  TCoords: (none)
  Tensors: (none)
  GlobalIds: (none)
  PedigreeIds: (none)
  EdgeFlag: (none)

So is it a bug or a misuse? Any idea ?

Thanks,
Julien.
p.s. doing the following doesn't help neither.
     assign->Assign("tensors", vtkDataSetAttributes::SCALARS,
vtkAssignAttribute::POINT_DATA);
instead of
     assign->Assign(vtkDataSetAttributes::TENSORS,
vtkDataSetAttributes::SCALARS, vtkAssignAttribute::POINT_DATA);
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