cell picker accuracy

[Brian Adams]

Hello All,
 
   I have a couple questions about the vtkCellPicker.

   First, how accurate is vtkCellPicker's GetPickPosition? We have been
trying to use it to draw contour lines on actors.  For a simple flat plane it
works perfectly,  the points collected (and hence the contour) is right on the
plane.  For a sphere, however, the picker isn't that nice to me.  The points
collected are elevated above the surface of the spear a certain distance.
(depending on how closely you were zoomed in when you picked them)  I thought
that changing the tolerance to something that seemed really small (like 0.0001)
would make a difference, but it doesn't seem to. Is there something about the
picker that I don't fully understand?

   My second question had to do with why changing the tolerance didn't work,
but I seem to have incorporated that into the first question. (too bad)

Thanks in advance for any way you can help,
Brian


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