The effect of rest frames on simulator sickness reduction

With increasing prevalence and capabilities of Virtual Reality (VR) as a part of education, entertainment, data analysis and industrial applications, the consideration of constructing a more user-friendly virtual environment becomes more important, which requires the reduction or elimination of simulator sickness (SS) -- a discomfort caused in simulated environment. As a form of motion sickness (MS) -- caused by movement in travel, some signs and symptoms of SS are the same as those of MS's, such as pallor, cold sweating, nausea, and vomiting. Several convincing theories or hypothesis to explain the cause of SS have been advanced, such as Sensory Conflict Theory, Postural Instability Theory and Rest Frames Hypothesis. Based on the first two theories aforementioned, high-quality tracking systems and modification of field of view (FOV) have been proposed to reduce the mismatch between visual perception and vestibular system in virtual environment (VE). Two main drawbacks exist in these techniques: (1) They will make uses weary in VE needs long distance physical navigation; (2) Modifying the field of view will decrease immersion.

To this end, inspired by the rest frame hypothesis and previous study on field of view, the goal of this research is to evaluate the effect of rest frames -- portions of the virtual environment that remain fixed in relation to the real world and do not move as the user moves around -- on SS reduction. A study was performed in this research, in which all participants experienced two different VR sessions: one with rest frames and the other without rest frames. The rest frames were developed by using a transparent cockpit attached with a black metal net in our experimental environment. A questionnaire asking users' discomfort was shown periodically in the VE during the study, which allowed us to record the level of participants' comfort in real time. Participants were required to finish a Simulator Sickness Questionnaire (SSQ) and a presence questionnaire after completing either session, to analyze the influence of rest frames on presence and their overall sickness induced by VR. Through comparing the time spent in VE, the real-time subjects' discomfort levels and scores of SSQ and presence questionnaire from both sessions, we found that rest frames have advantages as follows:

(1) Users could experience VEs without physical navigation;

(2) Rest frames significantly helped users acclimate to VR;

(3) The level of discomfort in VR was reduced;

(4) The level of presence was not impacted.