Investigating the effects of density and opacity of rest frames for VR sickness reduction

Abstract

One of the side effects of VR experiences, VR sickness, resembles real motion sickness and can cause discomfort for VR users. Rest Frame (RF) is a set of virtual objects independent of the virtual environment (VE) that serve as fixed visual elements. Previous research has shown that using RF can reduce VR sickness. However, a constantly visible RF in the user’s field of view may obstruct objects in the VE and cause a decrease in the field of view, thereby impairing user presence. This study consists of two experiments aimed at exploring configurations of RF that minimize a decrease in presence while maximizing the reduction of VR sickness. In the first experiment, RF configurations with varying levels of opacity and density were tested during virtual travel. Eighteen VR users provide real-time responses regarding their level of VR sickness. After each of the three sessions, participants completed a Simulator Sickness Questionnaire (SSQ) to assess VR sickness and the Witmer & Singer Presence Questionnaire (WS) to evaluate presence. Results indicated that changes in RF density did not significantly affect either VR sickness or presence. The second experiment, planned based on the findings of the first, compared the most effective RF (opacity 0.4, density 0.4) identified in the initial experiment to a no-RF condition with twelve participants. Results confirmed that the most effective RF reduced VR sickness compared to the absence of RF. These findings highlight the importance of appropriate RF design in improving user comfort and suggest practical guidelines for developing immersive virtual environments.