繪製四面體(切割後封閉)

參考url：https://lorensen.github.io/VTKExamples/site/Cxx/GeometricObjects/Cell3DDemonstration

效果圖：

實現：

vtkSmartPointer<vtkUnstructuredGrid> MakeTetrahedron(){
    // Make a tetrahedron.
    int numberOfVertices = 4;

    vtkSmartPointer<vtkCellArray> cellArray =
      vtkSmartPointer<vtkCellArray>::New();

    vtkSmartPointer< vtkPoints > points =
      vtkSmartPointer< vtkPoints > :: New();
    points->InsertNextPoint(0, 0, 0);
    points->InsertNextPoint(1, 0, 0);
    points->InsertNextPoint(0, 1, 0);
    points->InsertNextPoint(0, 0, 1);

    points->InsertNextPoint(3, 0, 0);
    points->InsertNextPoint(4, 0, 0);
    points->InsertNextPoint(3, 1, 0);
    points->InsertNextPoint(3, 0, 1);
    {
        vtkSmartPointer<vtkTetra> tetra =
          vtkSmartPointer<vtkTetra>::New();
        for (int i = 0; i < numberOfVertices; ++i)
        {
            tetra->GetPointIds()->SetId(i, i);
        }
        cellArray->InsertNextCell(tetra);
    }
    {
        vtkSmartPointer<vtkTetra> tetra =
          vtkSmartPointer<vtkTetra>::New();
        for (int i = 0; i < numberOfVertices; ++i)
        {
            tetra->GetPointIds()->SetId(i, i+4);
        }
        cellArray->InsertNextCell(tetra);
    }

    vtkSmartPointer<vtkUnstructuredGrid> unstructuredGrid =
      vtkSmartPointer<vtkUnstructuredGrid>::New();
    unstructuredGrid->SetPoints(points);
    unstructuredGrid->SetCells(VTK_TETRA, cellArray);
    //unstructuredGrid->InsertNextCell(VTK_TETRA, 4, )

    return unstructuredGrid;
}


int main(int argc, char *argv[])
{
    vtkSmartPointer<vtkUnstructuredGrid> test = MakeTetrahedron();
    vtkSmartPointer<vtkPlane> plane =
      vtkSmartPointer<vtkPlane>::New();
    plane->SetOrigin(0,0,0.5);
    plane->SetNormal(0.0, 0.0, -1.0);

    vtkSmartPointer<vtkClipDataSet> clipper =
      vtkSmartPointer<vtkClipDataSet>::New();
    clipper->SetInputData(test);
    clipper->SetClipFunction(plane);
    //clipper->SetValue(0);
    clipper->Update();

    vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
    mapper->SetInputData(clipper->GetOutput());

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

    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    renderer->AddActor(actor);

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

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

    vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
        vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
    renderWindowInteractor->SetInteractorStyle(style);
    renderWindowInteractor->Start();

    return 0;
}