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