[vtkusers] how to iterate over extracted edges?

[David Doria]

On Thu, Jan 14, 2010 at 4:14 PM,  <lynx.abraxas at freenet.de> wrote:
>
> On 12/01/10 14:55:11, David Doria wrote:
>> It may be helpful in cases like this for some of the experienced
>> members to give a "not that I've seen/heard of" type of response. A
>> few negative responses from some experienced members can be very
>> useful to decide if he should go ahead and write something himself.
>> What I'm imagining is happening if people don't know the answer, they
>> are just not responding in hopes that someone else will know the
>> answer and respond. However, sometimes the answer is "no one knows the
>> answer/ such a filter does not exist" and this can be inferred by a
>> few "I don't knows".
>>
>
> So  I'm  stuck  again:  I  want  to  iterate  over  the edges of the output of
> vtkDelaunay3D. I triede the following code but it never  reports  any  angles.
> Why's that? It seems there's no GetNextCell() ever.
>
> Thanks for any help or hints.
> Lynx
> _________________________________________
>
>
>        vtkExtractEdges *edges= vtkExtractEdges::New();
>        edges->SetInputConnection(delaunay3D->GetOutputPort());
>
>        //vtkCellArray *lines= delaunay3D->GetOutput()->GetLines(); //does this work as well?
>        vtkCellArray *lines= edges->GetOutput()->GetLines();
>        vtkPoints *epoints = edges->GetOutput()->GetPoints();
>
>        //unsigned int num_e= lines->GetNumberOfCells();
>
>        cout << "Computing angles... " << endl;
>        double angle;
> //         for(int i= 0; i << num_e; i++){
> //             angle= vtkMath::Dot(vtkMath::Normalize(lines->Get),
> //             }
>
>        vtkIdType npts, *pts;
>        double p0[3], p1[3];
>
>        lines->InitTraversal();
>        while(lines->GetNextCell(npts, pts)){
>            if (npts != 2){
>                cout << "Didn't get two points! Skipping edge!" << endl;
>                continue;
>                }
>            epoints->GetPoint(pts[0], p0);
>            epoints->GetPoint(pts[1], p1);
>            vtkMath::Normalize(p0);
>            vtkMath::Normalize(p1);
>            angle= acos(vtkMath::Dot(p0, p1)) * 180.0 / PI;
>            cout << angle << "; ";
>            }
>        cout << endl;

Lynx,

It seems to work for me...

Try the data file (cow.vtp) from here:
http://www.cmake.org/Wiki/VTK/Examples/Modelling/Cxx/Delaunay3D

with this example:
http://www.cmake.org/Wiki/VTK/Examples/ExtractEdges

Does it do what you needed?

Thanks,

David