[vtkusers] how to get output from a vtkTransformFilter ?

[Amy Squillacote]

Actually, vtkPoints is a concrete class, not an abstract one, and 
vtkPolyData is a subclass of vtkPointSet, not vtkPoints.

Did you call Update() on the vtkTransformFilter before trying to get the 
points from its output? If not, then the output was not filled in yet, 
which is necessary before asking for its points.

If your dataset if a vtkPolyData, then use vtkTransformPolyDataFilter 
because it is optimized for working with vtkPolyData.

- Amy

M.Salman at surrey.ac.uk wrote:
>
> Hi,
> I am not an expert in VTK just a normal user so my opinion may be 
> wrong.One problem I see is to use an instance of vtkPoints which is an 
> abstract class,I guess the output of the filter must be assigned to 
> some concrete instance of any of a class derived from vtkPoints such 
> as vtkPolyData.
> This is how I normally do this kind of stuff
>
>
> vtkTransformFilter* tf= vtkTransformFilter::New();
> vtkPolyData* data=vtkPolyData::New();//this polydata contains the 
> points which you need to change
> vtkPolyData* result=vtkPolyData::New();
> ......//Apply changes to the the transform instance
> .....
> .....
> vtkTranformPolyDataFilter * pdf= vtkTranformPolyDataFilter::New();
> pdf->SetInput(data);
> pdf->SetTransform(tf);
> pdf->Update();
>
> result= pdf->GetOutput();
>
> result contains the changed version of data you can use GetPoints 
> method to get changed points
>
> This is how I do it and I am sure there must be some more elegant and 
> short way to do it .
>
> Regards
> M.Salman
> University of Surrey,U.K.
>                         
>
>                                                                                                     
>
>
>
> -----Original Message-----
> From: vtkusers-bounces+m.salman=surrey.ac.uk at vtk.org on behalf of 
> Emmanouil Moschidis
> Sent: Thu 03/05/2007 3:09 PM
> To: vtkusers at vtk.org
> Subject: [vtkusers] how to get output from a vtkTransformFilter ?
>
> Hi
> i am using a vtkTransformFilter to change the coordinates of some 
> points. I apply the filter to the points and then i want to get the 
> output but when the following line is executed:
>
> vtkPoints *Tdata=Tf->GetOutput()->GetPoints(); //Tf is the 
> vtkTransformFilter
>
> i get this error:
>
> ERROR: In 
> /Users/antoinerosset/VTK/Filtering/vtkDemandDrivenPipeline.cxx, line 
> 635 vtkStreamingDemandDrivenPipeline (0x17bc1e50): Algorithm 
> vtkTransformFilter(0x1e61a790) did not create output for port 0 when 
> asked by REQUEST_DATA_OBJECT and does not specify a concrete 
> DATA_TYPE_NAME.
>
>
> Does Anyone know what's wrong? Is there any other way of getting 
> output (the modified points) from a vtkTransformFilter?
> thanks
>
>       
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-- 
Amy Squillacote
Kitware, Inc.
28 Corporate Drive
Clifton Park, NY 12065
Phone: (518) 371-3971 x106