[vtkusers] error message in subdividing a cell

[Jochen]

Okay, here we go. Should we ever meet the beers go on you. ;-)

Most of the things were correct.
The main problem was you missed one important thing.
When you create a vtkPolyData by hand from an vtkUnstructuredGrid you must
copy the cells as well, not only the points.
So the reason no triangles could have been found was simply that no
triangles did exist.



// Catch mouse events
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
    static MouseInteractorStyle* New();

    MouseInteractorStyle() {
        selectedMapper = vtkSmartPointer<vtkDataSetMapper>::New();
        selectedActor = vtkSmartPointer<vtkActor>::New();
        selected = vtkSmartPointer<vtkUnstructuredGrid>::New();

        // the next 5 lines can be done once here in the constructor. 
        // It's not necessary to do this with every pick
        selectedMapper->SetInput(selected);
        selectedActor->SetMapper(selectedMapper);
        selectedActor->GetProperty()->EdgeVisibilityOn();
        selectedActor->GetProperty()->SetEdgeColor(1,0,0);
        selectedActor->GetProperty()->SetLineWidth(3);
    }


    virtual void OnLeftButtonDown()
    {
        int* pos = this->GetInteractor()->GetEventPosition();
        vtkSmartPointer<vtkCellPicker> picker =
            vtkSmartPointer<vtkCellPicker>::New();
        picker->SetTolerance(0.0005);
        picker->Pick(pos[0], pos[1], 0, this->GetDefaultRenderer());
        double* worldPosition = picker->GetPickPosition();

        if(picker->GetCellId() != -1)
        {
            vtkSmartPointer<vtkIdTypeArray> ids =
                vtkSmartPointer<vtkIdTypeArray>::New();
            ids->SetNumberOfComponents(1);
            ids->InsertNextValue(picker->GetCellId());

            vtkSmartPointer<vtkSelectionNode> selectionNode =
                vtkSmartPointer<vtkSelectionNode>::New();
            selectionNode->SetFieldType(vtkSelectionNode::CELL);
            selectionNode->SetContentType(vtkSelectionNode::INDICES);
            selectionNode->SetSelectionList(ids);

            vtkSmartPointer<vtkSelection> selection =
                vtkSmartPointer<vtkSelection>::New();
            selection->AddNode(selectionNode);

            vtkSmartPointer<vtkExtractSelection> extractSelection =
                vtkSmartPointer<vtkExtractSelection>::New();

            extractSelection->SetInput(0, this->Data);
            extractSelection->SetInput(1, selection);
            extractSelection->Update();

            selected->ShallowCopy(extractSelection->GetOutput());

            vtkSmartPointer<vtkPolyData> newdata =
                vtkSmartPointer<vtkPolyData>::New();
            newdata->SetPoints(selected->GetPoints());

          *  // you missed to copy the cells
            // it's not enough to copy points only

           
/**********************************************************************/
            newdata->SetPolys(selected->GetCells());
           
/**********************************************************************/
*
            // the triangle filter is not necessary
            // but see my comment in the main function
            //vtkSmartPointer< vtkTriangleFilter > triangleFilter =
            //	vtkSmartPointer<vtkTriangleFilter>::New();
           
//triangleFilter->SetInputConnection(newdata->GetProducerPort());
            //triangleFilter->Update(); // not necessary

            int numberOfSubdivisions = 1;

            vtkSmartPointer< vtkLoopSubdivisionFilter >
subdivisionFilter =
                vtkSmartPointer<vtkLoopSubdivisionFilter>::New();
           
subdivisionFilter->SetNumberOfSubdivisions(numberOfSubdivisions);
            subdivisionFilter->SetInput(newdata);
           
//subdivisionFilter->SetInputConnection(triangleFilter->GetOutputPort());

            subdivisionFilter->Update(); // not necessary
            // show the subdivsions
           
selectedMapper.SetInputConnection(subdivisionFilter.GetOutputPort());
            // comment the line above and uncomment the next code line if
you prefer 
            // to show the selected cell as a whole
            // selectedMapper.SetInputConnection(selected.GetOutputPort());

            // ???
            //vtkSmartPointer<vtkIdTypeArray> id =
vtkSmartPointer<vtkIdTypeArray>::New();
            //id->SetNumberOfComponents(1);
        }

        vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
    }

    vtkSmartPointer<vtkPolyData> Data;
    vtkSmartPointer<vtkDataSetMapper> selectedMapper;
    vtkSmartPointer<vtkActor> selectedActor;
    vtkSmartPointer<vtkUnstructuredGrid> selected;
};

vtkStandardNewMacro(MouseInteractorStyle);


int main(int, char *[])
{
    vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
    sphereSource->Update(); // not necessary

    vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();

    // next commented lines are only necessary if you want to 
    // subdivide the complete sphere at once and not only the selected cell 
    /*
    vtkSmartPointer<vtkTriangleFilter> triangleFilter =
    vtkSmartPointer<vtkTriangleFilter>::New();
    triangleFilter->SetInputConnection(sphereSource->GetOutputPort());
    triangleFilter->Update();
    mapper->SetInputConnection(triangleFilter->GetOutputPort());
    */
    // instead use the spheresource directly as input
    mapper->SetInputConnection(sphere->GetOutputPort());

    vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
    actor->SetMapper(mapper);

    vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
    vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
    renderWindow->AddRenderer(renderer);

    vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor
=
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
    renderWindowInteractor->SetRenderWindow(renderWindow);
    renderWindowInteractor->Initialize();

    vtkSmartPointer<MouseInteractorStyle> style =
        vtkSmartPointer<MouseInteractorStyle>::New();
    style->SetDefaultRenderer(renderer);

    /* see my comment several lines above */
    //style->Data = triangleFilter->GetOutput();
    style->Data = sphere.GetOutput();
    renderWindowInteractor->SetInteractorStyle(style);

    renderer->AddActor(actor);
    renderer->ResetCamera();
    renderer->SetBackground(0,0,1); // Blue

    renderWindow->Render();
    renderWindowInteractor->Start();

    return EXIT_SUCCESS;
} 


with best regards
Jochen


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