1. A method, comprising: detecting, by a computer executing a non-tactile three dimensional (3D) user interface, a focus gesture made by a hand positioned within a field of view of a sensing device coupled to the computer; upon detecting the focus gesture, conveying a prompt to unlock the user interface; subsequently, receiving, by the computer, a set of multiple 3D coordinates representing a gesture by the hand, the gesture comprising a rising motion along a vertical axis in space; and transitioning the non-tactile 3D user interface from a locked state to an unlocked state upon detecting completion of the gesture.