[vtkusers] Picking a point

[Robb Brown]

I've got a cube and I want to pick a point on it's surface.  
vtkPointPicker is kind of slow and when I use 
vtkPointPicker.GetMapperPosition() it returns the wrong position (I 
create a sphere centered on the coordinates and it is not under the 
mouse)

vtkPropPicker is a much nicer option -- very fast, and allows you to 
give it a subset of the props to pick.  However, 
vtkPropPicker.GetPickPosition() does not appear to return world 
coordinates.  To me, these look like view coordinates.  I tried 
multiplying by the camera's ViewTransformMatrix, but this doesn't 
produce good results.  I also asked the renderer to convert from view 
to world coordinates and this produced completely nonsensical numbers.

How can I do this?

Thanks,

Robb
_____________________________
Robb Brown
Seaman Family MR Center
Calgary, AB