The Rolling Ball

Interactive graphics systems often need techniques that allow the user to rotate graphical objects freely in three-dimensional space using commonly-available two-dimensional input devices such as a mouse. Achieving this goal is hampered by the fact that there is no single natural mapping from the two parameters of the input device to the three-parameter space of orientations. Here we i n troduce the rolling-ball method for mouse-driven three-dimensional orientation control, along with some of its interesting extensions to other scientiic visualization problems. This technique exploits a continuous two-dimensional motion modeled after that of a ball rolling without slipping on a at table to reach a n y arbitrary three-dimensional orientation. Unlike a v ariety of other methods, the rolling-ball approach has only a single state and is completely context-free: one can turn oo the mouse cursor and ignore 1