[vtkusers] vtk picking

[Tracy]

Hello Everyone,

It is my first time to use vtkPicker and its subclasses. Unfortunately, I 
never get any code works well
for me regardless of writing by myself or downloading from Internet. One 
example is from
http://public.kitware.com/pipermail/vtkusers/2004-April/073344.html, but it 
looks that
"vtkCommand::EndPickEvent" doesn't show any effect, if I use 
"LeftButtonPressEvent"
instead of "EndPickEvent" , the printed value is always "-1" ,which means I 
never picked
any point. Anybody can tell me why?

Actually what I want to do is to pick a specific cell, retrieve the position 
of picked cell
and change the colour and property based on the user requirements.I think it 
shouldn't be difficult,
but don't know why I get so much trouble.

Anyone can give me a rough C++ programming structure to implement this 
function?
Your help is greatly appreciated!


Regards
Tracy