[vtk-developers] [vtkusers] vtkDataSetSurfaceFilter - Cell Picking

[Bhanu Hariharan]

David,
As you suggested, I got it to work using SetGlobalIds and then retrieving
that using GetGlobalIds. Many thanks for your patience and help.


-Bhanu

On Wed, Mar 6, 2013 at 11:41 AM, Bhanu Hariharan <bhanu at petrotel.com> wrote:

> David,
>
> I am using vtk 5.2 - is it possible that this function was not defined in
> that version.
>
> I get the error that SetOriginalCellIdsName is not a member of
> vtkDataSetSurfaceFilter   :(
>
> Bhanu
>
>
>
> On Wed, Mar 6, 2013 at 10:36 AM, David E DeMarle <dave.demarle at kitware.com
> > wrote:
>
>> Give DSF a name for the array.
>> SetOriginalCellIdsName("idsintoDSForsomething")
>> Then retrieve it from the output like
>> DSF->GetOutput()->GetCellData()->GetArray("idsintoDSForsomething")
>>
>>
>> David E DeMarle
>> Kitware, Inc.
>> R&D Engineer
>> 21 Corporate Drive
>> Clifton Park, NY 12065-8662
>> Phone: 518-881-4909
>>
>>
>> On Wed, Mar 6, 2013 at 11:29 AM, Bhanu Hariharan <bhanu at petrotel.com>wrote:
>>
>>>
>>> David,
>>>
>>> I had turned on PassThroughCell. But I do not know how to access the new
>>> Ids array after the fact.
>>> VTK Doc says something about a 'OrginalCellIds' but I am not sure how to
>>> access this.
>>> So I extracted the output of DSF to a vtkPolyData but still cant figure
>>> out how to get to that new Ids array.
>>> Any help with that is really appreciated.
>>>
>>> I will try your other suggestion in the meantime.
>>>
>>> Thanks,
>>> Bhanu
>>>
>>>
>>> On Wed, Mar 6, 2013 at 9:25 AM, David E DeMarle <
>>> dave.demarle at kitware.com> wrote:
>>>
>>>> Sorry for the confusion, it has been a long time since I added that
>>>> code the DataSetSurfaceFilter. Turning PassThroughCell/PointIds in fact
>>>> generates a new Ids array, which you can retrieve after the fact to do the
>>>> lookups into the data that is input to the DSF and extract particular
>>>> cells/points by their offset (n'th cell in the cell array, n'th point in
>>>> the point array)
>>>>
>>>> However I still recommend making your own ids array and using that
>>>> instead of PassThrough. vtkIdFilter will generate them for you. The array
>>>> marked as the active global ids array is treated specially by most filters
>>>> in that they try to preserve it across operations (including threshold and
>>>> DSF). We added this to VTK a few years ago specifically for this case of
>>>> finding out where particular result values come from (and in particular for
>>>> surface selection). So the Threshold and surface filter will push globalIDS
>>>> forward just fine. Once you get a result, grab the active globaIDs array,
>>>> look for the values in it, and look them up in the original data. The
>>>> extract selections filter will do the job of looking them up in the
>>>> original data and pulling them out as a new dataset.
>>>>
>>>>
>>>> David E DeMarle
>>>> Kitware, Inc.
>>>> R&D Engineer
>>>> 21 Corporate Drive
>>>> Clifton Park, NY 12065-8662
>>>> Phone: 518-881-4909
>>>>
>>>>
>>>> On Wed, Mar 6, 2013 at 10:02 AM, Bhanu Hariharan <bhanu at petrotel.com>wrote:
>>>>
>>>>> David,
>>>>> Thanks for replying. However I have a doubt.
>>>>> Are you suggesting the VTKUnstructuredgrid should have an globalids
>>>>> array? Is that what the member is called - globalIds? I actually pass
>>>>> VTKUnstructuredgrid  to a VTKThreshold filter and then pass that filter to
>>>>> VTKdatasetsurfacefilter.
>>>>>
>>>>> Perhaps you can post a couple lines of code. That would be very
>>>>> helpful.
>>>>> Thanks,
>>>>> Bhanu
>>>>>
>>>>>
>>>>>
>>>>> On Tue, Mar 5, 2013 at 6:55 PM, David E DeMarle <
>>>>> dave.demarle at kitware.com> wrote:
>>>>>
>>>>>> The input data should have a globalids array containing a unique
>>>>>> value for each cell. If it does, extract will preserve it. After the
>>>>>> extraction, use that array in the polydata to do the look up to the
>>>>>> original cell in the unstructured grid.
>>>>>> On Mar 5, 2013 6:00 PM, "Bhanu Hariharan" <bhanu at petrotel.com> wrote:
>>>>>>
>>>>>>> Hi All,
>>>>>>>
>>>>>>> I need some help doing the following. Please could one of you guide
>>>>>>> me on how.
>>>>>>>
>>>>>>> I use a vtkDataSetSurfaceFilter on VTKUnstructuredGrid to render
>>>>>>> skin of that grid. That works fine and I can see the number of surfaces
>>>>>>> shown by grabbing the
>>>>>>> dataSetSurfaceFilter->GetOutput()->GetNumberOfCells().
>>>>>>>
>>>>>>>
>>>>>>> I need a way to map the surface back to the original cell id. That
>>>>>>> is if I have 2 cells and I render just skin, number of surfaces rendered
>>>>>>> are 10. I need to be able to pick on any of these 10 surfaces and map them
>>>>>>> back to either of the the 2 grid cells.
>>>>>>>
>>>>>>>
>>>>>>> http://www.vtk.org/doc says :
>>>>>>>
>>>>>>> If PassThroughCellIdsOn is 1, then the output polygonal dataset will
>>>>>>> have a celldata array that holds the cell index of the original 3D cell
>>>>>>> that produced each output cell. This is useful for cell picking.
>>>>>>> I turned the PassThroughCellIds On and I have UseStrips turned off.
>>>>>>>
>>>>>>> Then I did
>>>>>>> vtkPolyData *surfacePolyData = dataSetSurfaceFilter->GetOutput();
>>>>>>>
>>>>>>> But I do not see how I can access that celldata array that holds the
>>>>>>> original 3D cells for the surfaces.
>>>>>>>
>>>>>>> Please can anyone advise on how.
>>>>>>>
>>>>>>> Thanks in advance.
>>>>>>> Bhanu
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>
>>>
>>
>
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