[vtkusers] How can I use vtkWorldPointPicker?

[cuckoo]

Hi,

I want find the x,y,z world coordinate of a screen x,y with a specified zBuffer value(between 0 and 1). when I use vtkWorldPointPicker as vtkCellPicker showed by the example "annotatePick.tcl", there is no annotation in the screen.
 
I just want use vtk to realize the function of "gluUnProject()" in OpenGL. But I don't know how to do it and how can I use vtkWorldPointPicker to obtain the world 
coordinate.

Hope you will respond. Thank you in advance.

cuckoo
 　　　　　　   　　　　　　　　　　　　　　 

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