[vtkusers] why does Updating scalars updates Delaunay Object too?

[David E DeMarle]

Since the pipeline cannot do it for you, I think you will have to
manually break the pipeline to keep Delauney from re-executing and
then manually copy the modified attributes into the right places in
your copy of Delauney's output data.

David E DeMarle
Kitware, Inc.
R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909



On Wed, Sep 14, 2011 at 10:41 AM, rakesh patil
<prakeshofficial at gmail.com> wrote:
> Hi,
>
> In the code above, the scalars contains depth information. Which is negative
> and positive both. So I want to convert positive values to negative. After
> converting that, when I say scalars modified, delaunay's object is executed.
> So is there any way to avoid the second time execution? Because when I load
> a big data of say 30-40lakhs points, first time triangulation itself takes
> ample amount of time. Then later when reversing the scalar, again
> triangulation consumes more time which I want to avoid. Is there any way to
> bypass it second time?
>
> Thanks
>
> Warm Regards
>
> Rakesh Patil
>
> On Wed, Sep 14, 2011 at 5:36 PM, David E DeMarle <dave.demarle at kitware.com>
> wrote:
>>
>> The pipeline isn't smart enough to differentiate between changes to
>> the geometry/topology and attributes (fairly easy to do) and to know
>> what matters to all of the downstream results (fairly hard to do). So
>> it takes the safe approach and says that if anything changes,
>> everything downstream must re-execute.
>>
>> David E DeMarle
>> Kitware, Inc.
>> R&D Engineer
>> 21 Corporate Drive
>> Clifton Park, NY 12065-8662
>> Phone: 518-881-4909
>>
>>
>>
>> On Wed, Sep 14, 2011 at 6:35 AM, rakesh patil <prakeshofficial at gmail.com>
>> wrote:
>> > Hello,
>> >
>> > vtkPoints *pnts = vtkPoints::New();
>> > pnts->SetNumberOfPoints(num);
>> >
>> > vtkDoubleArray *scalar = vtkDoubleArray::New();
>> > scalar->SetNumberOfTuples(num);
>> >
>> >
>> > vtkCellArray *pVertex = vtkCellArray::New();
>> >
>> > for (vtkIdType i = 0; i < num; i++)
>> > {
>> >    readFile >> xval >> yval >> zval;
>> >    pnts->InsertPoint(i, xval, yval, 0);
>> >    scalar->InsertTuple1(i, zval);
>> >
>> >    pVertex->InsertNextCell(1, &i);
>> > }
>> >
>> > vtkPolyData *pd = vtkPolyData::New();
>> > pd->SetPoints(pnts);
>> > pd->SetVerts(pVertex);
>> > pd->GetPointData()->SetScalars(scalar);
>> >
>> > vtkDelaunay2D *del = vtkDelaunay2D::New();
>> >
>> > del->SetInput(pd);
>> > del->SetTolerance(0.00001);
>> > del->Update();
>> >
>> > vtkPolyDataMapper *mapp = vtkPolyDataMapper::New();
>> > mapp->SetInputConnection( del->GetOutputPort() );
>> > mapp->ScalarVisibilityOn();
>> >
>> >
>> > vtkActor *actor = vtkActor::New();
>> > actor->SetMapper(mapp);
>> > actor->GetProperty()->SetColor(1, 0, 0);
>> > actor->GetProperty()->SetPointSize(3);
>> >
>> > renderer->AddActor(actor);
>> >
>> > After adding actor to the renderer, suppose I do some changes in the
>> > scalar
>> > array, and say modified, I observe that delaunay object is also updated
>> > and
>> > again triangulation takes place.
>> >
>> >
>> > Why is this so?
>> > ;
>> >
>> > _______________________________________________
>> > Powered by www.kitware.com
>> >
>> > Visit other Kitware open-source projects at
>> > http://www.kitware.com/opensource/opensource.html
>> >
>> > Please keep messages on-topic and check the VTK FAQ at:
>> > http://www.vtk.org/Wiki/VTK_FAQ
>> >
>> > Follow this link to subscribe/unsubscribe:
>> > http://www.vtk.org/mailman/listinfo/vtkusers
>> >
>> >
>
>