Disconnect endpoints in vtkPolyData

Support
1

Hi All,

I am trying to create an arc suing vtkPolyData and it works well
except I don’t want the ends to be connected. I just want ti to be
like ‘C’. I tried to remove the last point but it still connects the
ends.

Here is the code:

double startAngle=0;
double stopAngle=270;
double radius=400;

vtkSmartPointer<vtkPoints>points =
        vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkCellArray> cells =
        vtkSmartPointer<vtkCellArray>::New();
points->SetNumberOfPoints(270);
cells->InsertNextCell(270);

for(double curAngle=startAngle;curAngle<stopAngle;curAngle++)
{
    cells->InsertCellPoint(curAngle);
}

for(double curAngle=startAngle;curAngle<stopAngle;curAngle++)
{
    double xCord=radius*cos(vtkMath::RadiansFromDegrees(curAngle));
    double yCord=radius*sin(vtkMath::RadiansFromDegrees(curAngle));
    points->SetPoint(curAngle,xCord,yCord,0);
    qDebug()<<curAngle;
}


vtkSmartPointer<vtkPolyData>arc=
        vtkSmartPointer<vtkPolyData>::New();
arc->Initialize();
arc->SetPolys(cells);
arc->SetPoints(points);

vtkSmartPointer<vtkPolyDataMapper>rectangleMapper=
        vtkSmartPointer<vtkPolyDataMapper>::New();
rectangleMapper->SetInputData(arc);
vtkSmartPointer<vtkActor>arcActor=
        vtkSmartPointer<vtkActor>::New();
arcActor->SetMapper(rectangleMapper);
arcActor->GetProperty()->SetColor(1,1,0);
arcActor->GetProperty()->SetLineWidth(5.0);
arcActor->GetProperty()->SetRepresentationToWireframe();
arcActor->SetOrigin(0,0,0);
arcActor->RotateZ(-90);
arcActor->GetProperty()->EdgeVisibilityOff();

Any hints?

Thanks,
Jothy

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2

Jothy,

A polygon is by definition a closed set of line segments. If you want to create a ‘C’ shape, this is a polyline. Then you have to store it in the Lines structure of the vtkPolyData. Technically you have to replace the call to arc->SetPolys(cells); by arc->SetLines(cells);.

Hope this helps,
Joachim

3

Thanks a lot, will try.