[away3d] How can I find if an object is on screen?

[jeff]

Is there a simple way to find out is an object is visible on the
screen (in the FOV and in front of the camera).  I tried using
camera.scene( ) method to get the actual x and y coordinates on the
screen, but objects behind the camera can have the same x and y as
objects in front of the camera.  I would use this in conjunction with
the Z of the object and camera, but my camera moves so the Z does not
help.  Any suggestions?  Thanks