[vtkusers] creating a vtkSpline to transform within a pipeline

[David Gobbi]

Hi Anant,

The example program that you are trying to run was made for VTK 6.  If
you have a copy of the VTK 5.10 source code, look for
Hybrid/Testing/Cxx/TestBSplineWarp.cxx and use that instead.

The vtkBSplineTransform doesn't manage missing points.  For that,
someone would need to add an algorithm to VTK like the one described
in this paper:

Seungyong Lee, George Wolberg, and Sung Yong Shin,
Scattered Data Interpolation with Multilevel B-Splines
IEEE Transactions on Visualization and Computer Graphics,
Vol. 3, pp. 228-244, 1997

 - David

On Mon, Sep 17, 2012 at 2:03 AM, Anant Vemuri <ajar108 at gmail.com> wrote:
> Hi David,
>
> Thanks... that is exactly what I want to do. I was wondering, how does it
> manage missing points.
>
> Another thing, I tried to compile the test program on vtk documentation
> website
>
> http://vtk.org/gitweb?p=VTK.git;a=blob_plain;f=Filters/Hybrid/Testing/Cxx/TestBSplineWarp.cxx
>
> and I get an error as,
>
> error: ‘class vtkBSplineTransform’ has no member named ‘SetCoefficientData’.
>
> Thanks,
> Anant.
>
>
> On Fri, Sep 14, 2012 at 2:37 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>
>> Hi Anant,
>>
>> If you recompute the spline coefficients within the transform's
>> Update() method, then it should provide the sort of pipeline behavior
>> that you are looking for.  The following paper describes the VTK
>> transform update mechanism:
>> http://www.ncbi.nlm.nih.gov/pubmed/12631510
>>
>> I added a vtkBSplineTransform to VTK 5.10.  It might satisfy your
>> needs, and if not, you might be able to re-use parts of it:
>> http://hdl.handle.net/10380/3252
>>
>>  - David
>>
>> On Fri, Sep 14, 2012 at 4:02 AM, Anant Vemuri <ajar108 at gmail.com> wrote:
>> > I am currently creating a spline using vtkSplineFilter. The points in
>> > the
>> > spline are changing as new positions for points are generated. However,
>> > now
>> > I want to put the position information into a vtkTransform and connect
>> > the
>> > Spline being created within a pipeline so that, it gets updated when the
>> > the
>> > transform changes.
>> >
>> > currently I am doing this whenever I get new positions. Is it possible
>> > to
>> > put this in a pipeline so that the points are updated using a
>> > vtktransform
>> > when the transform changes. In vtkTransform there is a function called
>> > "MultiplyPoint" and "TransformPoint", however both are not indicated to
>> > be
>> > pipelined.
>> >
>> > I am curious if anyone has tried to do this, or if anyone has
>> > suggestions on
>> > this issue.
>> >
>> > myspline is a class containing vtkPoints, vtkPolyLine, vtkPolyData etc.
>> >
>> >
>> >     //   In the constructor for my spline class
>> >     _points       = vtkSmartPointer< vtkPoints >::New();
>> >     _polyLine     = vtkSmartPointer< vtkPolyLine >::New();
>> >     _cells        = vtkSmartPointer< vtkCellArray >::New();
>> >     _polyData     = vtkSmartPointer< vtkPolyData >::New();
>> >     _splineFilter = vtkSmartPointer< vtkSplineFilter >::New();
>> >     _tubeFilter   = vtkSmartPointer< vtkTubeFilter >::New();
>> >
>> >     //   PIPELINE
>> >     _cells->InsertNextCell(_polyLine);
>> >     _polyData->SetPoints(_points);
>> >     _polyData->SetLines(_cells);
>> >     _splinefilter->SetInput( _polyData );
>> >     _splinefilter->SetMaximumNumberOfSubdivisions( 48 );
>> >     _tubeFilter->SetInputConnection( _splineFilter->GetOutputPort());
>> >     _tubeFilter->SetNumberOfSides( 12 );
>> >     _tubeFilter->SetRadius( 5.0 );
>> >     _tubeFilter->SetCapping(true);
>> >     _mapper->SetInputConnection( _tubeFilter->GetOutputPort() );
>> >     _actor->SetMapper(_mapper);
>> >     _actor->GetProperty()->SetLineWidth(4);
>> >
>> >     //----------------------------------------------------------------
>> >     // Updating for new vtkpoints
>> >
>> >     // I want to put this part into the pipeline if possible so that
>> >     // i can apply a vtkTransform to lets say the _points and the spline
>> >     // gets updated automatically. The updated _points that I get are
>> >
>> >     // absolute positions so I cannot appl
>> >     splineObj->getPoints()->Reset();
>> >     splineObj->getPolyLine()->GetPointIds()->Reset();
>> >     vtkIdType k = 0;
>> >
>> >     // __scanorder contains the order in which the points need to be put
>> > into a spline
>> >     // __positions contains the updated point locations
>> >     for (int j = 0; j < __scanOrder.size(); j++)
>> >     {
>> >          unsigned int __idx = __scanOrder[i][j]-1;
>> >          double &__coord = __positions[__idx]->getCoordinate();
>> >
>> >
>> >
>> > splineObj->getPoints()->InsertNextPoint(__coord[0],__coord[1],__coord[2]);
>> >          splineObj->getPolyLine()->GetPointIds()->InsertNextId( k );
>> >          k++;
>> >     }
>> >     splineObj->getCellArray()->Reset();
>> >     splineObj->getCellArray()->InsertNextCell(splineObj->getPolyLine());
>> >     splineObj->getPolyData()->Modified();
>> >
>> >
>> > Thank you,
>> >
>> > Anant.
>
>