VTK: display subdivided polygon - vtk

Question

I have created an icosahedron and subdivided it, I am not trying to display it but it seems to be displaying it un-subdivided. Here is my code:
vtkSmartPointer<vtkPlatonicSolidSource> icosahedron = vtkSmartPointer<vtkPlatonicSolidSource>::New();
icosahedron->SetSolidTypeToIcosahedron();
icosahedron->Update();
cout << " Centre is " << icosahedron->GetOutput()->GetCenter()[0] << ", " << icosahedron->GetOutput()->GetCenter()[1] << ", " << icosahedron->GetOutput()->GetCenter()[2] << endl;
cout << " There are " << icosahedron->GetOutput()->GetNumberOfPolys() << " triangles." << endl;
cout << " there are " << icosahedron->GetOutput()->GetNumberOfPoints() << " points " << endl;
vtkSmartPointer<vtkPolyDataAlgorithm> subdivisionFilter;
subdivisionFilter = vtkSmartPointer<vtkLinearSubdivisionFilter>::New();
dynamic_cast<vtkLinearSubdivisionFilter *> (subdivisionFilter.GetPointer())->SetNumberOfSubdivisions(2);
subdivisionFilter->SetInput(icosahedron->GetOutput());
subdivisionFilter->Update();
cout << " After " << endl;
std::cout << " There are " << subdivisionFilter->GetOutput()->GetNumberOfPoints() << " points." << std::endl;
std::cout << " There are " << subdivisionFilter->GetOutput()->GetNumberOfPolys() << " triangles." << std::endl;
vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection(subdivisionFilter->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);
//Add the actors to the scene
renderer->AddActor(actor);
renderer->SetBackground(.1, .2, .3);
//Render and interact
renderWindow->Render();
renderWindowInteractor->Start();
The console output is:
Centre is 0, 0, 0
There are 20 triangles.
there are 12 points
After
There are 162 points.
There are 320 triangles.
Confirming that it has indeed been subdivided.

Answer 1

I can see the divisions after turning on wireframe mode:
#include <vtkProperty.h>
....
actor->GetProperty()->SetRepresentationToWireframe();
What you are seeing is that the algorithm is adding the new points in the same plane as the existing triangle, so when you render the result as a surface it does not look any different.