[Paraview-developers] Replacement of SetInput with SetInputData (VTK5 vs. 6)

[Berk Geveci]

Sounds good.

>> Finally, store the results in the output vtkDataObject

This should be done by copying the output of the inner filter to the output
of the outer filter. I would advise against directly setting the internal
output as the DATA_OBJECT() in the output information of the outer filter.
It will probably work but you may run into weird issues downstream
depending on what you do.

Best,
-berk

On Thu, Apr 30, 2015 at 1:13 AM, Schlottke, Michael <
M.Schlottke at aia.rwth-aachen.de> wrote:

>  Hi Berk,
>
>  Ah, that is good to know. So my typical setup in RequestData for a
> custom filter should be something like the following:
>
>  - connect the first internal filter to the input vtkDataObject using
> SetInputData()
> - use SetInputConnection() to chain up any internal filters I use (if
> possible)
> - finally, store the results in the output vtkDataObject
>
>  Is this a good approach to follow under normal circumstances or am I
> missing something here?
>
>  Michael
>
>   On 28 Apr 2015, at 15:50 , Berk Geveci <berk.geveci at kitware.com> wrote:
>
>  Replace that Update() with cp->Update().
>
>  The rule for internal filters is that you should never use
> SetInputConnection() to connect anything to an external filter from within
> RequestData(). You don't want internal pipeline executions to propagate to
> external filters as it may cause all kinds of problems. SetInputData() does
> not create a pipeline connection so it is safe to use in such
> circumstances. SetInputConnection() is safe to connect internal filters to
> each other.
>
>  Best,
> -berk
>
> On Tue, Apr 28, 2015 at 2:54 AM, Schlottke, Michael <
> M.Schlottke at aia.rwth-aachen.de> wrote:
>
>> Hi Utkarsh,
>>
>> Thank you very much for this answer, it clears things up a lot. Am I
>> right to sum this up as a rule of thumb to
>>
>> “use SetInputConnection whenever possible, resort to SetInputData where
>> it isn’t”
>>
>> for most use cases?
>>
>> On a related note, I’ve encountered a few filters with code like this:
>>
>> //////////////////////////////////////////////////////////////
>> vtkMyFilter::RequestData(….)
>> {
>>   …
>>   vtkCellDataToPointData* cp = vtkCellDataToPointData::New();
>>   ...
>>   vtkUnstructuredGrid* pdata = cp->GetUnstructuredGridOutput();
>>   pdata->GetPointData()->RemoveArray(“arrayname");
>>   pdata->GetPointData()->Update();
>>   pdata->Update(); // will not compile with VTK6 (******)
>>
>>   vtkInformation *outInfo = outputVector->GetInformationObject(0);
>>   vtkUnstructuredGrid *output =
>> vtkUnstructuredGrid::SafeDownCast(outInfo->Get(vtkDataObject::DATA_OBJECT()));
>>   output->SetPoints(pdata->GetPoints());
>>   output->CopyStructure(pdata);
>>   output->GetCellData()->PassData(pdata->GetCellData());
>>
>>   return 1;
>> }
>> //////////////////////////////////////////////////////////////
>>
>> I am wondering about the line marked with (******). Is it obsolete with
>> VTK6 (as there is no Update() method for non-vtkAlgorithm objects), should
>> I call cp->Update() instead, or is there something entirely different to do
>> to make this code work properly?
>>
>> Regards,
>>
>> Michael
>>
>> > On 27 Apr 2015, at 19:53 , Utkarsh Ayachit <utkarsh.ayachit at kitware.com>
>> wrote:
>> >
>> >> Now I am wondering: ifinside the RequestData method of a filter, do I
>> *ever*
>> >> need  to use SetInputConnection, and if yes, how?
>> >
>> >
>> > Here's an example:
>> >
>> > vtkMyFilter::RequestData(....)
>> > {
>> >   vtkDataSet* myinput = vtkDataSet::GetData(inputInformation[0], 0);
>> >
>> >   vtkNew<vtkSomeFilter> filter1;
>> >   filter1->SetInputData(myinput);
>> >
>> >   vtkNew<vtkSomeFilter> filter2;
>> >   filter2->SetInputConnection(filter1->GetOutputPort());
>> >   ...
>> >
>> >   filter2->Update()
>> > }
>> >
>> > Thus, for internal pipelines, it makes sense to use SetInputConnection.
>> >
>> >> It seems like all filters
>> >> I’ve had a look at always access the input data object (which I can
>> only
>> >> pass on using SetInputData, not SetInputConnection), not the input
>> port.
>> >> However, as a user with little VTK experience it seems like this might
>> >> “break” the aforementioned pipeline?
>> >
>> > It the example I gave, for example, if you use SetInputData() to pass
>> > the output of filter1 to filter2, you'll need to call
>> > filter1->Update() before doing that. Otherwise, filter1 has not
>> > execute and hence doesn't have valid data to pass to filter2. Unlike
>> > the old SetInput(), setting the dataset using SetInputData() doesn't
>> > preserve the pipeline information i.e. filter2 will not update filter1
>> > just because you called filter2->Update() if SetInputData() is used to
>> > pass the data.
>> >
>> > Hope that clarifies it a little.
>>
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