[fernanor]

Hello all,

I'm not sure this is the correct forum for this, but here goes anyway.

So I wrote a couple of ParaView filters in C++, namely a reader A for a custom file format deriving from vtkUnstructuredGridAlgorithm, and a filter B that takes two of these outputs as input and does some calculation on them.

Everything is working fine, but now I noticed that I need to pass a single string value (and 3-4 numbers) from each reader to the actual filter B doing stuff.
A use case would be, for example, passing the input data filename from a reader to a filter on to a writer plugin, which can use it to come up with an appropriate output filename.

Now the work-around I'm using at the moment to pass these data to the filter B is abusing CellData or PointData arrays of the vtkUnstructuredGrid generated in A. Needles to say this is not very elegant and creates other problems too.

I think that somehow I need to create an appropriate vtkInformationKey storing the data.
However, for everything I tried, the key seems to disappear in the pipeline between the filters.

Here is some pseudocode snippet to show what I tried to add a value to an vtkInformation.
Here the reader class A:

class A : vtkUnstructuredGridAlgorithm {
  static vtkInformationStringKey* MYSTRING();
   ...
}

vtkInformationKeyMacro(A, MYSTRING, String);

A::RequestInformation(...) {
  vtkSmartPointer<vtkInformation> outInfo = outputVector->GetInformationObject(0);
  outInfo->Set(A::MYSTRING(),"test");
}

And the filter class B:

#include "classA.h"
class B : vtkUnstructuredGridAlgorithm {
   ...
}

B::RequestInformation(...) {
  vtkSmartPointer<vtkInformation> inInfo = inputVector[0]->GetInformationObject(0);
  if (!inInfo->Has(A::MYSTRING()))
     std::cout << "fail" std::endl;

}

I keep getting fails printed to my console

So here is the question(s):
Is this the correct approach using vtkInformation?
If yes, what am I doing wrong? The ImageFoo example on the wiki page does exactly the same. Can someone give me a detailed explanation on the step necessary, or a well commented example?

If no,is there a better, or more paraviewesque way to do it, and can I get hint at what I need to look at please?
Any other comments on how to pass user defined data along the pipeline?

Thanks alot for the help,
Oli

P.S.: I'm using ParaView 5.0.0