[Paraview] questions concerning vtkFloatArray

[Burlen Loring]

Hi Natalie,
Some comments follow:

>  int dims[3],i,j,k;
>  // pointer for casting
>  vtkRectilinearGrid *rect_input = vtkRectilinearGrid::New();
>  vtkStructuredGrid *structgrid_input = vtkStructuredGrid::New();
>
>
>  vtkDataArray *scaldat = this -> 
> vtkAlgorithm::GetInputArrayToProcess(0,input);
>  vtkDataArray *new_scaldat;
>
>  vtkFloatArray *scalars = vtkFloatArray::New();
>  vtkFloatArray *new_scalars = vtkFloatArray::New();
>
>  scalars = vtkFloatArray::SafeDownCast(scaldat); //this is now the 
> input as vtkFloatArray

This is going to create a memory leak. You New()'d a vtkFloatArray and 
never called Delete() before reassigning.

>  if((DataSetType == VTK_RECTILINEAR_GRID) && (rect_input = 
> vtkRectilinearGrid::SafeDownCast(input)))
>   {
>    rect_input -> GetDimensions(dims);
>   }
>
>  else if((DataSetType == VTK_STRUCTURED_GRID )&& (structgrid_input = 
> vtkStructuredGrid::SafeDownCast(input)))
>  {
>  structgrid_input->GetDimensions(dims);
>  }
>

Also these are going to create leaks. You never call Delete() on the 
data sets you New()'d before reassigning.

> My first problem occurs in the part, where I already got the input 
> Scalar array and casted it to vtkFloatArray. In order to perform 
> arithmetic operations with the data in it, I want to assign each point 
> of the vtkFloatArray to a "real" float array, but to do that, I need 
> to get the vtkIDList of the vtkFloatArray , so I can use the 
> GetPoint(vtkId x)-method.
>
> How do I get a vtkIDList of my vtkFloatArray?
There is no GetPoint() method for a vtkFloatArray. Do you mean GetTuple? 
The Tuples are ordered such the tuple 0 is associated with point/cell 0 
for point/cell data arrays. Are you looking to get the points associated 
with the data set or the scalar values associated with the points?
>
> secondly,
> i don´t really now how to set the output correctly.
> I want to use a method like CopyStructure() so that the grid is copied 
> from input to output, but as the input is a DataSet and the output 
> StructuredGrid, does this method compute points and so for the 
> structuredGrid Format or do I have to assign them manually?
CopyStructure, does copy the geometry. Both the source and destination 
data set have to be the same type.

>
> Thirdly, I don´t know how to assign my new vtkFloatArray as Attribute 
> Data to the output. SetScalars() does not work here, the compiler says 
> that this is not a member function of vtkStructuredGrid. But surely 
> there must be a method to assign attribute data to a structured grid?
if you have point data then you can:

output->GetPointData()->AddArray(someArray);

There are similar calls for CellData and FieldData.

I would advise taking a close look at the examples in the vtk user 
guide. In the filters I have seen you will implement RequestData and get 
the input and output from an instance of vtkInformation. here is an 
example using unstructured grids:

int MyPv3Filter::RequestData(
        vtkInformation *req,
        vtkInformationVector **input,
        vtkInformationVector *output)
{
  vtkDataObject *tmpDataObj;
  // Get the inputs
  tmpDataObj
    = input[0]->GetInformationObject(0)->Get(vtkDataObject::DATA_OBJECT());
  vtkUnstructuredGrid *usgIn
    = dynamic_cast<vtkUnstructuredGrid *>(tmpDataObj);
  // Get the outputs
  tmpDataObj
    = output->GetInformationObject(0)->Get(vtkDataObject::DATA_OBJECT());
  vtkUnstructuredGrid *usgOut
    = dynamic_cast<vtkUnstructuredGrid *>(tmpDataObj);
 
  // do stuff here

  return 1;
}

In regard to the input arrays, they can be easily obtained from 
PointData, CellData, or FieldData via a call such as

usgIn->GetPointData()->GetArray(x).
>
> thx,
> Natalie
>
> ------------------------------------------------------------------------
> Express yourself instantly with MSN Messenger! MSN Messenger 
> <http://clk.atdmt.com/AVE/go/onm00200471ave/direct/01/>
> ------------------------------------------------------------------------
>
> _______________________________________________
> ParaView mailing list
> ParaView at paraview.org
> http://www.paraview.org/mailman/listinfo/paraview
>   


-- 
Burlen Loring
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x137