[vtkusers] How to get cell ids of duplicate points in vtkMergePoints?

[Kiran, P (CORP, GEITC)]

Hi all:

I have set of 3D points contained in vtkPolyData., in which some of them are
duplicated.
For my application, I want to find the ids of duplicated points.

I looked at vtkMergePoints,  where we can check whether point is duplicated
or not. 
If there are some duplicated points, is it possible to  get the id's of
those points?

Can someone thorugh some light on how to do this.

Thanks in advance for help
Kiran