hello, could someone briefly describe the diferences between the various ROS navigation packages? There's at least http://wiki.ros.org/navigation, http://wiki.ros.org/3d_navigation, and http://wiki.ros.org/nav2d. The description of http://wiki.ros.org/navigation says its a A 2D navigation stack but the video (with the PR2) shows it avoiding a 3D obstacle (person holding a plank). If it is indeed a 2D navigation stack what is nav2d for? If it is indeed a 3D navigation stack then what is 3d_navigation for?

thanks!