Investigating Depth of Field Blur as a Strategy for Mitigating Cybersickness in Virtual Reality

<p dir="ltr"><b>In recent years, Virtual Reality (VR) on Head Mounted Displays (HMD) has been used in a wide variety of both serious and entertainment applications, including therapy, training, and gaming. However, while these technologies are more widely accessible than ever before, their use continues to be impeded by cybersickness, a condition characterized by symptoms including nausea, headaches, eye-strain, and dizziness. This malaise has historically stymied generations of VR devices, and presents a considerable barrier to the wide-scale adoption of VR.</b></p><p dir="ltr">The rendering of Depth of Field (DoF) blur is a promising tool for mitigating cybersickness in HMD VR. This rendering manipulation can be applied to existing applications with relatively little developer effort or computational cost. DoF blur is theorized to improve comfort through multiple mechanisms, including the provision of a reliable depth cue to minimize the accommodation-vergence conflict, manipulation of visual attention to avoid discomfiting shifts in vergence, or allocation of visual attention to the periphery, and/or through masking rendering imperfections.</p><p dir="ltr">This thesis involves four user studies, investigating the role and effect of DoF blur in mitigating cybersickness. Study 1 involves assessing the impact of DoF blur on the accommodation-vergence conflict in modern HMD using a sparse environment, in which monocular depth cues are omitted, and the view position and orientation are fixed. Results suggest that cybersickness in such a constrained environment and interaction scheme is minimal, and while DoF aids the speed and accuracy of depth perceptions, it has no effect on cybersickness. Study 2 expands on the design of Study 1, with the introduction of a more interesting visual background, some monocular depth cues, and wide angle head motions. Again, results show minimal cybersickness, suggesting that neither a static nor dynamic accommodation-vergence conflict contribute significantly to cybersickness. The rendering of DoF improves the speed and accuracy of depth perceptions, but this did not translate into any improvement in cybersickness outcomes.</p><p dir="ltr">Study 3 assesses the effects of DoF on cybersickness caused by exploration of a fully featured virtual environment. Unlike in the first two studies, participants experienced severe cybersickness from locomoting through this environment, resulting in multiple participants withdrawing from the severity of their sickness. The rendering of DoF results in a significant decrease in this withdrawal rate, suggesting that even in modern HMDs, this algorithm is effective in improving comfort outcomes. Finally, Study 4 compares the effect of DoF blur to a virtual cursor, which provides a fixation point in the centre of the field of view and is known to guide attention. Results suggest that while the DoF blur may guide attention, it does not do so in the same way as a cursor.</p><p dir="ltr">This thesis concludes that the rendering of DoF blur is effective in mitigating cybersickness on modern HMDs. We found no evidence that this reduction is achieved through mitigation of the accommodation-vergence conflict. Exploratory analysis of the effect of this blur on participant head movement shows it to be limited, implying an attentional or otherwise purely visual mechanism.</p>