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

Mon Mar 11 17:30:15 EDT 2013

One related question though. I started using Surface Filter really only for
performance reasons.

I was thinking if I rendered just surface cells, the rendering and rotation
etc would be must faster.
However I do not find it any different than when I render all cells. What
am I missing?
Any reasons anyone can think of, please let me know.

Thanks,
Bhanu

On Mon, Mar 11, 2013 at 4:12 PM, Bhanu Hariharan <bhanu at petrotel.com> wrote:

> 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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