[vtkusers] Polygon Selection by Mouse -- How?

[Tao Tao]

Hi, All:
   If I use the mouse to point to one polygon in my terrain model (which is
a simple vtkPolyData object) on screen, how can I map the mouse position
from the render window (x,y) coordinates to the terrain model (x,y)
cooordinates?

My objective is to highlight whatever polygon the mouse click on.

Thanks!