Abstract
Our previous reports indicate that the severity of visually induced motion sickness, (VIMS), can be predicted, to some extent, by a total amount of visual rotation, such as yaw, pitch, and roll, in a limited period in a consistent viewing condition. The visual rotation, however, is not uncertain as to whether it is in terms of optic flow, a pattern of apparent motion of a visual scene caused by relative motion between an observer and a scene, or retinal flow. To clarify this, we conducted an experiment, in which five-minute CG moving image with a first person point of view was presented three times with five-minute break between them using head-mounted display (Oculus VR, Oculus Rift cv1). There were two conditions: (i) Head-movement condition, in which observers move their heads so that visual target moving right/left or upward/downward relative to the display was aligned with display-fixed visual alignment, and (ii) Head-stationary condition, in which observers fixed their heads so that visual target being stationary relative to the display was, again, aligned with display-fixed visual alignment. Observers answered Simulator Sickness Questionnaire, (SSQ), four times: just before viewing the moving image, at the first and second break, and just after finishing the viewing. The results showed that SSQ total score significantly increase every measurement time (p < 0.01), while there’s no significant difference between the conditions (p < 0.1). This suggests that the severity of VIMS can be predicted in terms of optic flow, but not retinal flow.