[vtkusers] Create a circle in a polydata

[David Doria]

I noticed that there is not a "vtkCircleSource". What is the best way
to create a circle in a polydata? I am trying to make varying size
circles for the vtkVoxelContoursToSurfaceFilter example. Should I use
vtkSphereSource and vtkCutter? Does it make sense to add a
vtkCircleSource class?

Thanks,

David