Frustum View Angle, Observer View Angle and VE Navigation

The issue of screen size is discussed with respect to the task of navigating in 3D computer graphics environments. Two variables are isolated, the observer’s visual field of view (observer VA) subtended by a screen, and the viewing frustum angle (frustum VA) determined by the computer graphics geometry. It is possible to have these set to be identical, which according to one hypothesis should lead to a stronger sense of situational awareness in the virtual environment. Another plausible hypothesis is that a wide (frustum VA) field of view will be the most important factor in situational awareness with the correct viewpoint being largely irrelevant. Two experiments are reported that examine these issues with respect to different tasks requiring situation awareness. The task in the first experiment was to find targets by navigating over a digital terrain model. The result showed that frustum field of view (frustum VA) was the most important predictor of search time. In the second experiment subjects were asked to rotate left or right by 45, 90 or 180 deg. For this task we predicted that having the correct viewpoint would be important but the results showed (contrary to our hypothesis) that a medium (60 deg.) frustum width gave the most accurate performance with viewpoint being a minor factor. These results exemplify the “robustness of visual perspective” phenomenon that has been reported by vision researchers.