Controlling Graphic Objects Naturally: Use Your Head

Roger A. Browse, James C. Rodger, Ian Sewell, and Jeffrey Brooke

Abstract

During normal viewing of an object, a human observer will typically make small movements in the position of the head resulting in small parallax-related image changes. The significance of these changes is apparent when viewing a static stereographic display. Since the observer expects modifications in viewing direction that accompany side to side head movements, the lack of such changes in viewing stereographic displays creates the striking illusion that the static display is rotating in a compensatory direction. Using head tracking, we generate the appropriate pairs of images on a stereographic display device in order to maintain a stable virtual stereo object for the viewer. Unnatural, but learnable mappings from input devices such as a mouse or a joystick are typically used to bring about changes in the viewing direction and viewing distance in graphic displays. As an alternative to these techniques, we have extended the use of the monitored head position, resulting in a display system that permits control of graphic objects with subtle head movements. The device permits a zone of small head movements for which there is no rotation or scaling of the virtual object, but only parallax-related images changes as projected to each eye. A slightly exaggerated head movement initiates rotation and/or scaling of the scene that terminates when the head returns to a central viewing position. We are carrying out experiments to test the performance of human subjects in tasks that require head movements to control the rotation of graphic objects. A preliminary study that only examines rotation around a single axis suggests that it may be a very effective and natural technique.