Odd normals pt1

unstructured_grid = vtk.vtkUnstructuredGrid()
unstructured_grid.SetPoints(points)
unstructured_grid.InsertNextCell(vtk.VTK_POLYHEDRON, face_stream)

# Get cube normals
cell = unstructured_grid.GetCell(0)
normals = vtk.vtkPolyDataNormals()
normals.SetInputData(cell.GetPolyData())
normals.ComputePointNormalsOff()
normals.ComputeCellNormalsOn()
normals.Update()
print
for i in xrange(cell.GetNumberOfFaces()):
    print i, "=>", normals.GetOutput().GetCellData().GetNormals().GetTuple(i)
# 0 => (-1.0, 0.0, 0.0)
# 1 => (1.0, 0.0, 0.0)
# 2 => (0.0, -1.0, 0.0)
# 3 => (0.0, 1.0, 0.0)
# 4 => (0.0, 0.0, -1.0)
# 5 => (0.5773502588272095, -0.5773502588272095, 0.5773502588272095) -> Odd Result