The Picker-Element picks with a point, a ray or with a line segment into the space and send a %pick-event% if it collide with a 3d object.
The picking and its duration in frames starts with %picking-activate-command%. 
The Picker-Element must be a child of a %group3D-element%.
See also %pick-ray-command%, %pick-line-segment-command% and %Pick-Point-Command%.