[Paraview-developers] How to implement an identity filter ?

houssen houssen at ipgp.fr
Sun Jul 19 13:53:22 EDT 2015 

Still get the zero filter ?!... Don't understand !? If somebody has an 
idea ?... Something to check ? Verify ? Track ? Something missing ? Add 
tag in xml ? Missing rendering call ?

Now, I derive from vtkDataObjectAlgorithm, I re-implement only 
RequestDataObject. I tried without success to create a new instance 
(from pInputObj) to pass to pOutputInfo (with and without using 
DeepCopy) : finally I tried to pass directly pInputObj. In the GUI, in 
the information tab, I get the expected type but zero point / cell. When 
I delete the filter, the initial data are still here (tab info indicates 
non zero number of points / cells) but the 3D viewpoint is empty : can 
this be a clue of some problem ?

Franck

int myFilter::RequestDataObject ( vtkInformation * ipRequest, 
vtkInformationVector ** ipInputVector, vtkInformationVector * 
opOutputVector )
{
   if ( !ipRequest ) return 0;

   vtkInformation * pInputInfo = ( ipInputVector ) ? ipInputVector[0] -> 
GetInformationObject ( 0 )            : NULL;
   vtkDataObject  * pInputObj  = ( pInputInfo    ) ? pInputInfo       -> 
Get ( vtkDataObject::DATA_OBJECT () ) : NULL;
   if ( pInputObj )
   {
     vtkInformation * pOutputInfo = ( opOutputVector ) ? opOutputVector 
-> GetInformationObject ( 0 )            : NULL;
     vtkDataObject  * pOutputObj  = ( pOutputInfo    ) ? pOutputInfo    
-> Get ( vtkDataObject::DATA_OBJECT () ) : NULL;
     if ( !pOutputObj )
     {
       _OutputDataType = pInputObj -> GetClassName (); // For later call 
to FillOutputPortInformation
       pOutputInfo -> Set ( vtkDataObject::DATA_OBJECT (), pInputObj );
       return 1;
     }
   }
   return 0;
}

int myFilter::FillOutputPortInformation ( int iPort, vtkInformation * 
ipInfo )
{
   if ( ipInfo ) ipInfo -> Set ( vtkDataObject::DATA_TYPE_NAME (), 
_OutputDataType.c_str () ); // Output data type to create (called after 
ProcessRequest)
   return 1;
}

Le 2015-07-15 23:49, houssen a écrit :
> Shawn, Joachim, thanks.
> After a quick look at the code, if I got you right, on a
> REQUEST_DATA_OBJECT request, I still need to create a new instance of
> the input and to set it as the DATA_OBJECT of the vtkInfo of the
> output. I still have to test this, but, I got the idea !
>
> Franck
>
> Le 2015-07-15 15:47, Shawn Waldon a écrit :
>> You might want to take a look at inheriting from
>> vtkPassInputTypeAlgorithm[1] if you want the output type to be the
>> same as the input type.  It already implements RequestDataObject the
>> way that I think Joachim is suggesting.
>>
>> HTH,
>> Shawn
>>
>> [1]:
>> 
>> http://www.vtk.org/doc/nightly/html/classvtkPassInputTypeAlgorithm.html
>> [14]
>>
>> On Wed, Jul 15, 2015 at 7:27 AM, Joachim Pouderoux
>> <joachim.pouderoux at kitware.com [15]> wrote:
>>
>>> Franck,
>>>
>>> You will have to override the RequestDataObject() method in order
>>> to make your filter generic. This method is the one called to
>>> generate the output data object.
>>> Take a look at vtkGenerateIndexArray.cxx for instance, I think you
>>> can just copy it in your class (which should be derivated from
>>> vtkDataObjectAlgorithm).
>>>
>>> Best,
>>>
>>> JOACHIM POUDEROUX
>>>
>>>> _PhD, Technical Expert_
>>>
>>> 2015-07-15 11:57 GMT+02:00 houssen <houssen at ipgp.fr [9]>:
>>>
>>>> Seems that it is not possible to filter on vtkDataObject type.
>>>> But with less generic types (like vtkUnstrucutredGrid for
>>>> instance), the myFilter works : no error occur, but, viewpoint
>>>> ends up to be empty. I get "zero" instead of "identity" : why ?!
>>>>
>>>> Franck
>>>>
>>>> Le 2015-07-14 23:38, houssen a écrit :
>>>>
>>>>> How to write an identity filter ? (1 input port, 1 output port,
>>>>> output = input whatever input may be)
>>>>>
>>>>> I need to write a custom filter. I am used to VTK "from
>>>>> outside"
>>>>> (creating/handling vtk pipelines/scene/object from a main
>>>>> program)
>>>>> that is basically without the need to understand all internal
>>>>> VTK
>>>>> mechanics (except the SetInputConnection concept). I am not
>>>>> yet used
>>>>> to VTK internal mechanics that is necessary for writing a
>>>>> ParaView
>>>>> plugin.
>>>>>
>>>>> I need my filter to do "complex" stuffs. As I couldn't make it
>>>>> work,
>>>>> I simplified as much as possible to obtain finally an identity
>>>>> filter
>>>>> (!) : this is still not working. I feel I still miss something
>>>>> from
>>>>> VTK internal mechanics.
>>>>>
>>>>> As far as I understand, in the constructor, I need :
>>>>> myFilter::myFilter () { SetNumberOfInputPorts  ( 1 );
>>>>> SetNumberOfOutputPorts ( 1 ); }
>>>>>
>>>>> So then I need to implement the FillXXXPortInformation :
>>>>> int myFilter::FillInputPortInformation ( int vtkNotUsed (
>>>>> iPort ),
>>>>> vtkInformation * ipInfo )
>>>>> {
>>>>>   if ( ipInfo ) ipInfo -> Set (
>>>>> vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE (), "vtkDataObject" );
>>>>> //
>>>>> Filter allowed data types
>>>>>   return 1;
>>>>> }
>>>>> int myFilter::FillOutputPortInformation ( int vtkNotUsed (
>>>>> iPort ),
>>>>> vtkInformation * ipInfo )
>>>>> {
>>>>>   if ( ipInfo ) ipInfo -> Set ( vtkDataObject::DATA_TYPE_NAME
>>>>> (),
>>>>> "vtkDataObject" ); // Output data type to be created
>>>>>   return 1;
>>>>> }
>>>>>
>>>>> So, now I only need to implement the ProcessRequest gateway:
>>>>> int myFilter::ProcessRequest ( vtkInformation * ipRequest,
>>>>> vtkInformationVector ** ipInputVector, vtkInformationVector *
>>>>> opOutputVector )
>>>>> {
>>>>>   if ( ipRequest && ipRequest -> Has (
>>>>> vtkDemandDrivenPipeline::REQUEST_DATA () ) )
>>>>>     if ( ipInputVector && opOutputVector ) opOutputVector =
>>>>> ipInputVector[0];
>>>>>    return Superclass::ProcessRequest ( ipRequest,
>>>>> ipInputVector,
>>>>> opOutputVector );
>>>>> }
>>>>>
>>>>> I believed that I would be the only steps to proceed to get an
>>>>> identity filter. When I use my identity filter in Paraview, I
>>>>> get
>>>>> errors like :
>>>>> ERROR: In
>>>>>
>>>>>
>>>>>
>>>>
>>>
>> 
>> /.../ParaView-v4.3.1-source/VTK/Common/ExecutionModel/vtkDemandDrivenPipeline.cxx,
>>>>> line 810
>>>>> vtkPVPostFilterExecutive : Input for connection index 0 on
>>>>> input port
>>>>> index 0 for algorithm vtkPVPostFilter(0x16d0ec0) is of type
>>>>> vtkDataObject, but a vtkPolyData is required.
>>>>>
>>>>> Some logic is still missing here : could somebody explain me
>>>>> what and why ?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Franck
>>>>>
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>>
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>> http://www.vtk.org/doc/nightly/html/classvtkPassInputTypeAlgorithm.html
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