Survey of Motion Sickness Mitigation Efforts in Virtual Reality
By
Benton Lane
Virtual reality, all things being equal, is still a relatively new technology that immerses users in a simulated environment. While VR has enormous potential in various fields such as education, gaming, and therapy, motion sickness remains a significant issue for many users. Motion sickness occurs when the user’s physical movement does not match their visual cues, leading to feelings of nausea, dizziness, and discomfort. To address this problem, various technologies have been developed to reduce motion sickness in VR. My intent with this essay is to explore the software and hardware solutions that have been developed, or are on the coming horizon, that are addressing motion sickness in VR.
One of the most common approaches to address motion sickness in VR is through software solutions. These solutions typically alter the user’s experience by adjusting visual cues or reducing motion in the virtual environment. For instance, some software solutions reduce the amount of blur or distortion in the user’s peripheral vision, which can reduce feelings of dizziness and nausea. Other software solutions use a fixed point of view or vignette to reduce peripheral motion, thus reducing the user’s discomfort. One example of a software solution is the “Comfort Mode” on Oculus headsets, which reduces the amount of movement and blurring in the user’s peripheral vision, providing a more comfortable VR experience.
Among the new approaches being developed, are that of Columbia Engineering Professor Steven K. Feiner and Ajoy Fernandes, with graphics software showing promising results in combating VR sickness. Their approach involves subtly changing the user’s field of view (FOV) in response to visually perceived motion while they remain physically stationary, which has been found to significantly reduce VR sickness. The team developed software that acts as a pair of “dynamic FOV restrictors,” which can partially obscure each eye’s view with a virtual soft-edged cutout. The researchers tested this method on a group of volunteers and found that when study participants used the FOV restrictors, they felt more comfortable and stayed in the virtual environment longer. Moreover, the degree of VR sickness experienced by participants can be significantly reduced without decreasing the participants’ sense of presence in the virtual environment, and without the majority of the participants even being aware of the intervention. Feiner and Fernandes plan to look into how FOV restrictors could help acclimate users to VR experiences, using different cutout shapes and textures. Their research has shown that VR sickness is a solvable challenge, and their method could make VR experiences more comfortable and compelling for a wider range of users.
However, while software solutions can help reduce motion sickness, they are not a perfect solution. For one, software solutions can alter the user’s experience by reducing the level of immersion or introducing artifacts that reduce the realism of the VR experience. Furthermore, the effectiveness of software solutions varies from user to user, with some users still experiencing motion sickness despite the software’s efforts.
Another approach to reducing motion sickness in VR is through increasing the frames per second (FPS) of the virtual environment. FPS is the number of still images displayed per second onscreen, and the higher the FPS, the smoother the virtual environment appears. A higher FPS can reduce the perceived motion and increase the sense of immersion in VR. This is because a higher FPS reduces the delay between the user’s movements and the virtual environment’s response, reducing the feeling of lag that can cause motion sickness.
The current industry standard for FPS in VR is 90 FPS, which is the minimum required to provide a smooth and comfortable VR experience. However, some newer VR devices can offer up to 120 FPS, which can further reduce motion sickness. For instance, the Pimax 8K X VR headset provides a 200-degree field of view and a 120 Hz refresh rate, providing a smooth and comfortable VR experience.
Additional methods of hardware improvements in this space include the increase of pixel density on the screens used in VR headsets. However, this is an area where VR deviates from typical screen measurements, instead of pixels per inch, VR measures pixels per degree. This PPD is the number of pixels per 1 degree that the eye perceives, given the curve of the lenses between the eye and the screen. For reference, the Meta Quest 2 has a PPD of 20, with the Quest Pro having a PPD of 22. Meta has demonstrated that they are researching pushing PPD as far as they can, and recently demonstrated a prototype headset approaching 55 PPD, with future goals looking at achieving a PPD of 60.
Despite the benefits of higher FPS and increases in PPD, there are also some drawbacks to consider. For one, higher FPS requires more powerful hardware, which can be expensive and limit the VR experience’s accessibility (not to mention the increased power requirements).. Additionally, higher FPS may not be enough to address all cases of motion sickness, as some users may still experience discomfort despite these gains.
Moving on to the next potential area of improvements is technology concerning interpupillary distance, or IPD. IPD refers to the distance between the user’s pupils, which varies from person to person. IPD is essential for a comfortable VR experience, as an incorrect IPD can lead to feelings of nausea, dizziness, and discomfort. It is standard for headsets available now to have manual, stepped IPD adjustments, but these do not cover the entire population accurately enough. Automatic IPD adjustments, when paired with eye tracking technology, can address this problem by adjusting the distance between the lenses in the VR headset to match the user’s IPD.
Devices such as the Playstation VR 2 and Varjo Aero use automatic IPD adjustments to provide a more comfortable VR experience. The devices measure the user’s IPD and adjust the distance between the lenses using small motors to match the user’s individual needs completely automatically, providing a more natural and immersive VR experience. This can significantly reduce the risk of motion sickness, as the user’s visual cues match their physical movement more closely.
Automatic IPD adjustments are a simple yet effective solution to address motion sickness in VR. However, not all VR devices have automatic IPD adjustments, and some devices may require manual adjustments, which can be time-consuming and potentially uncomfortable for the user.
Returning to the software side of solutions, a technique called foveated rendering is a graphics technology that reduces the computational resources required to render a VR scene by rendering only the portion of the scene that the user is currently looking at in high resolution. The technique takes advantage of the human eye’s limited resolution, as the central part of the eye, the fovea, has a higher resolution than the surrounding areas. By rendering only the central part of the scene in high resolution, foveated rendering can significantly reduce the computational resources required to render the scene, improving performance and reducing motion sickness.
Devices such as, again, the PSVR 2 and Varjo headsets use foveated rendering to provide a more comfortable VR experience. By reducing the computational load required to render the VR scene, these devices can achieve higher FPS and reduce the perceived lag between the user’s movements and the virtual environment’s response, reducing motion sickness.
However, foveated rendering is still a relatively new technique, and not all VR devices support it. Additionally, foveated rendering can introduce artifacts or reduce the realism of the VR experience, which may impact immersion, and requires the software developers to take advantage of the techniques effectively.
In summary, motion sickness remains a significant challenge for VR developers, but various technologies have been developed to address this issue. Software solutions – like foveated rendering and adaptive fields of view – and hardware solutions – like increased FPS and automatic IPD adjustments – are among the most common approaches that are being used to reduce motion sickness in VR. While these technologies can provide a more comfortable and immersive VR experience, they each have their limitations and drawbacks. As VR technology continues to evolve, it is likely that new technologies and techniques will need to be developed to provide an even more comfortable and immersive VR experience.
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