[vtkusers] Algorithm base class question

[Philippe P. Pebay]

Amy Squillacote wrote:
> Benjamin Schindler wrote:
>> Hi
>>
>> Thanks for the very quick response. The problem I have behind is, that
>> upon calling GetOutput on the Algorithm, I get a:
>>
>> vtkStreamingDemandDrivenPipeline (0x910fbb0): Algorithm
>> vtkSPHSliceFilter(0x91e0650) returned failure for request:
>> vtkInformation (0x914b438)
>>   Debug: Off
>>   Modified Time: 1918
>>   Reference Count: 1
>>   Registered Events: (none)
>>   Request: REQUEST_DATA_OBJECT
>>   ALGORITHM_AFTER_FORWARD: 1
>>   FORWARD_DIRECTION: 0
>>   FROM_OUTPUT_PORT: 0
>>
>> I guessed, that since vtkPointSetAlgorithm (according to the docs) takes
>> same input as output. I assumed this is the case even if you override
>> FillInputPortInformation. So switching over to vtkPointSetAlgorithm did
>>
> 
> No, the whole point of overriding FillInputPortInformation is to change
> the type of input an algorithm expects.

For an other example of that, using vtkTable (as opposed to vtkPointSetAlgorithm) for inputs as well as outputs, you may 
look at vtkStatisticsAlgorithms in VTK/Infovis. It will also show you how to distinguish between mandatory and optional 
ports while overriding FillInputPortInformation.

P.


> 
>> not solve my problems. I attached the source of the filter, but I'm not
>> sure it helps, because I put a breakpoint on every function in the
>> source file and never hit any before getting the error
>> Any ideas?
>>
>> Thanks
>> Benjamin
>>
>> On Mon, 2008-10-27 at 10:28 -0500, Amy Squillacote wrote:
>>
>>> Hi Benjamin,
>>>
>>> You could create a vtkPointSetAlgorithm and override its
>>> FillInputPortInformation method so that it takes a vtkMultiBlockDataSet
>>> rather than a vtkPointSetAlgorithm. Take a look at how this method is
>>> overridden in VTK/Graphics/vtkThreshold.cxx.
>>>
>>> - Amy
>>>
>>> Benjamin Schindler wrote:
>>>
>>>> Hi
>>>>
>>>> I'm writing for testing a filter that takes a MultiBlockDataSet and
>>>> outputs a PointSet. What base-class is most suitable for this kind of
>>>> filter? I looked at PointSetAlgorithm, but the doc says it must also
>>>> take a PointSet as input...
>>>>
>>>> Thanks
>>>> Benjamin
>>>>
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>>>>
>>>>
>>>>
> 
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> Amy Squillacote                    Phone: (256) 726-4839
> Computer Scientist                 Fax: (256) 726-4806
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-- 
Philippe Pebay
Sandia National Laboratories