Don't Block the Ground: Reducing Discomfort in Virtual Reality with an Asymmetric Field-of-View Restrictor

Although virtual reality has been gaining in popularity, users continue to report discomfort during and after use of VR applications, and many experience symptoms associated with motion sickness. To mitigate this problem, dynamic field-of-view restriction is a common technique that has been widely implemented in commercial VR games. Although artificially reducing the field-of-view during movement can improve comfort, the standard restrictor is typically implemented using a symmetric circular mask that blocks imagery in the periphery of the visual field. This reduces users' visibility of the virtual environment and can negatively impact their subjective experience. In this paper, we propose and evaluate a novel asymmetric field-of-view restrictor that maintains visibility of the ground plane during movement. We conducted a remote user study that sampled from the population of VR headset owners. The experiment used a within-subjects design that compared the ground-visible restrictor, the traditional symmetric restrictor, and a control condition without FOV restriction. Participation required navigating through a complex maze-like environment using a controller during three separate virtual reality sessions conducted at least 24 hours apart. Results showed that ground-visible FOV restriction offers benefits for user comfort, postural stability, and subjective sense of presence. Additionally, we found no evidence of negative drawbacks to maintaining visibility of the ground plane during FOV restriction, suggesting that the proposed technique is superior for experienced users compared to the widely used symmetric restrictor.