[vtkusers] How to make a filter operate on either mutable directed or mutable undirected graph

[David Doria]

On Wed, Mar 31, 2010 at 2:13 PM, Jeff Baumes <jeff.baumes at kitware.com> wrote:
> I see. Yes, in this case you need to specify the output type (directed
> or undirected graph) since the input is not a graph. I think you
> should override FillOutputPortInformation() to specify this, rather
> than overriding RequestDataObject(), although perhaps you should
> override both in this case.
>
> Jeff

Hi Jeff,

Yes, I forgot to mention that the input isn't always a vtkGraph to my
vtkGraphAlgorith m filters.

Case 1: The input IS a graph

You are right. In the case that FillInputInformation is not
re-implemented (the input is a vtkGraph) then you are correct, it
works as expected out of the box.

Case 2: The input is not a vtkGraph

I tried NOT re-implementing RequestData object and only
re-implementing FillOutputPortInformation as:

int vtkMeshToGraph::FillOutputPortInformation(
  int vtkNotUsed(port), vtkInformation* info)
{
  // now add our info
  info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkMutableUndirectedGraph");
  return 1;
}

but got the error:

vtkStreamingDemandDrivenPipeline (0x8a22a80): Algorithm
vtkMeshToGraph(0x8a229e8) returned failure for request: vtkInformation
(0x8a25e38)

With both FillOutputPortInformation AND RequestDataObject
re-implement, it worked fine. But it also worked fine with ONLY
RequestDataObject re-implemented.

Oh, the mysteries of the pipeline... haha

Thanks,

David