The perception of egomotion.

Egomotion is defined as any environmental displacement of the observer. Twenty stationary observers viewed computer-generated films that simulated rectilinear egomotion of constant speed and altitude over an endless plain. The heading point could be 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, or 90 degrees to an observer's right of the screen center. The screen was 53 degrees wide. Hence, there was a constant heading toward a point on the horizon, but the heading point was not always in view. The typical observer's mean pointing bias was 5.56 degrees to his right and his SD pointing error was 5.18 degrees. The results indicate that these abstract view samples of a pure egomotion ambient optic array are equally effective in giving rise to a compelling perception of egomotion. The results also indicate that observers can perceive the direction of their heading whether or not the heading point is in the view, although accuracy did vary slightly with the specific view. A pointing control using linear perspective scenes whose vanishing points fell off-view showed the same pattern of pointing errors with an overall rightward pointing bias of 3.19 degrees and with an SD pointing error of 3.04 degrees.