[vtkusers] Why does a vtkFeatureEdge return non-scalar output?

[Cory Quammen]

On Tue, May 1, 2018 at 10:52 PM pnt1614 <minpu.code at gmail.com> wrote:

> I am using a vtkFeatureEdge to extract a boundary edges and everything
> works
> fine. Now I want to render points on the boundary edge so I try to use
> vtkEdgePoints but there is an "No scalar data to contour
> " error. I found out that the boundary edge has no scalars. Is there
> something missing? or is this a bug?
>

vtkFeatureEdges does indeed copy data arrays to its output, so that is not
the problem. vtkEdgePoints expects a point data array to use for
interpolating points along edges. However, vtkSTLReader does not create any
point data arrays - I'm not sure STL files can even store data arrays.

If you just want to render the points in the vtkPolyData extracted from
vtkFeatureEdges, call

edgeActor->GetProperty()->SetRepresentationToPoints();

HTH,
Cory


>
>
>                 // Load a stl file
>                 //...
>                 vtkSmartPointer<vtkPolyData> data =
> pSTLReader->GetOutput();                            //
> vtkPolyData 형식으로 받아오기
>
>
>                                                   // Create a mapper and
> actor
>                 vtkSmartPointer<vtkPolyDataMapper> mapper =
> vtkSmartPointer<vtkPolyDataMapper>::New();
>                 mapper->SetInputData(data);
>
>                 vtkSmartPointer<vtkActor> actor =
> vtkSmartPointer<vtkActor>::New();
>                 actor->SetMapper(mapper);
>
>
>                 //---------------edges-----------
>                 vtkSmartPointer<vtkFeatureEdges> edges =
> vtkSmartPointer<vtkFeatureEdges>::New();
>                 edges->SetInputConnection(pSTLReader->GetOutputPort());
>                 edges->BoundaryEdgesOn();
>                 edges->FeatureEdgesOff();
>                 edges->ManifoldEdgesOff();
>                 edges->NonManifoldEdgesOff();
>                 edges->Update();
>
>                 int test = edges->GetColoring(); // the result is 1
>
>                 vtkSmartPointer<vtkPolyDataMapper> edgeMapper =
> vtkSmartPointer<vtkPolyDataMapper>::New();
>                 edgeMapper->SetInputConnection(edges->GetOutputPort());
>
>                 vtkSmartPointer<vtkActor> edgeActor =
> vtkSmartPointer<vtkActor>::New();
>                 edgeActor->SetMapper(edgeMapper);
>                 edgeActor->GetProperty()->SetLineWidth(3.0);
>
>
>                 vtkSmartPointer<vtkEdgePoints> e_points =
> vtkSmartPointer<vtkEdgePoints>::New();
>                 e_points->SetInputConnection(edges->GetOutputPort());
>                 e_points->SetValue(1150);
>                 e_points->Update();
>
>                 vtkSmartPointer<vtkActor> e_a =
> make_an_actor(e_points->GetOutputPort());
>
>                 vtkSmartPointer<vtkRenderer> renderer =
> vtkSmartPointer<vtkRenderer>::New();
>                 renderer->AddActor(e_a);
>
>
>
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-- 
Cory Quammen
Staff R&D Engineer
Kitware, Inc.
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