    aPolygon = vtkPolygon()

    aPolygon.GetPointIds().InsertNextId(22)
    aPolygon.GetPointIds().InsertNextId(23)
    aPolygon.GetPointIds().InsertNextId(24)
    aPolygon.GetPointIds().InsertNextId(25)
--
    polygon = vtkPolygon()
    polygon.GetPointIds().SetNumberOfIds(number_of_vertices)
    for i in range(0, number_of_vertices):
        polygon.GetPointIds().SetId(i, i)

    ug = vtkUnstructuredGrid()
--
    polygon = vtkPolygon()
    polygon.GetPoints().DeepCopy(points)
    polygon.GetPointIds().SetNumberOfIds(4)  # The 4 corners of the square
    for i in range(4):
        polygon.GetPointIds().SetId(i, i)

--
    polygon = vtkPolygon()
    polygon.GetPointIds().SetNumberOfIds(4)  # make a quad
    polygon.GetPointIds().SetId(0, 0)
    polygon.GetPointIds().SetId(1, 1)
    polygon.GetPointIds().SetId(2, 2)
    polygon.GetPointIds().SetId(3, 3)
--
    polygon = vtkPolygon()
    polygon.GetPointIds().SetNumberOfIds(numberOfVertices)
    for i in range(0, numberOfVertices):
        polygon.GetPointIds().SetId(i, i)

    ug = vtkUnstructuredGrid()
--
    polygon = vtkPolygon()
    polygon.GetPointIds().SetNumberOfIds(numberOfVertices)
    for i in range(0, numberOfVertices):
        polygon.GetPointIds().SetId(i, i)

    ug = vtkUnstructuredGrid()
