[vtkusers] How to pick a 3D point without the z-buffer?

[Mathieu Coursolle]

Hi VTK-Users,

I am using VTK on OSX with Core-Animation enabled. Therefore, I am  
unable to use any picking
algorithm that use the glReadPixel to retrieve the z-buffer, as the  
openGL scene seems to be flattened
at the end of the drawing process.

I am trying to figure out a way to pick a 3D point in space from a  
list of known pickable actors.

So let's say I have a collection of actors I know I can pick from, and  
a 2D view coordinate where the
mouse was clicked;
Is there a class/function in VTK that could be used to detect the  
intersection of the
vector going from the near plane to the far plane in parallel  
projection, and the nearest actor from the
list of pickable ones?

Thanks!

Mathieu