I always say that most of my readers know VR far better than me. For sure this is the case of Rob Farquarson-Cole that you surely know because he comments a lot on this and other VR blogs under the nickname “R FC”.
Rob first tried VR in 1991 and has become an enthusiast of the tech ever since. Because of his background in industrial design, he has always had a strong interest in the design and the ergonomics of the VR headsets. At Immersive Computing (see his Instagram account) he carries on this interest, exploring the technology always starting from the human perspective, putting the human at the center of his experiments and analysis. This post is the result of such kind of experimentations on the Valve Index headset.
In various comments he has written, he has highlighted his expertise regarding comfort and ergonomics of virtual reality headsets and how these characteristics are important to:
- ensure the correct presentation of the virtual world to the user by ensuring optimum optical alignment;
- ensure the headset does not interfere with immersion by causing discomfort, even for longer duration sessions.
Actually, both of them are right, based on their “headset fit”, or more specifically their “individual craniofacial anthropometry”, the technical term for the measurements that are used to describe the human head and face. When you start looking closely at craniofacial anthropometry, you will see a wide range of variance and facial asymmetry, as there are few if any people with perfectly symmetrical faces. And this is where things become more complicated when designing consumer equipment like virtual reality headsets, as there are few other products on the market that are worn so intimately against the face whilst secured to the head.
Examples of head measurements (Image by Rob Cole)
Other examples are scuba diving masks or full-face motorcycle helmets, although neither of these has the added complication of housing a head-mounted display that relies on a good fit for the correct optical presentation of the display to the eyes.
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Historically, virtual reality systems were prohibitively expensive and were limited to being used in controlled conditions by a small number of researchers, scientists, and groups like astronauts. It was typical to customize headsets to suit these users, just as spacesuits were made to fit specific astronauts. Additionally, the headsets were used for task-specific work purposes, where comfort would take a back seat to the task in hand, and the duration of sessions was often short.
However, following the release of consumer equipment like the HTC Vive, Oculus Rift, Sony PSVR and the various mobile VR headsets, we now have a different situation with a much larger group of people (the general population) using virtual reality on a regular basis, for longer periods of time. The larger this group of users, the more craniofacial variation is found, which has a direct impact on the quality of the virtual reality experience and whether users continue to use their headsets on a regular basis.
A “good fit” is comfortable to wear and ensures that the optical presentation is correct to truly immerse the user in their virtual world. A “bad fit” is uncomfortable (can be painful) and often causes a poor optical presentation which breaks immersion. A bad fit is simply a bad fit and not something that can just be easily adjusted away with headset straps or fiddling with the IPD (interpupillary distance) adjuster. If it doesn’t fit properly, it won’t ever fit properly, like a pair of ill-fitting shoes that don’t get better with time but continue to cause problems.
A bad fit can cause physical fatigue to the soft tissue of the face and hard bones of the head, creating stress which makes the experience unpleasant, and can contribute to a tendency towards motion sickness especially when combined with heat inside the headset. A bad fit with poor optical alignment has a negative effect on the feeling of “immersion” and “presence” as it interferes with the suspension of disbelief, by constantly reminding the user they are wearing a headset – its hard to relax into your experience when one of your eyes is slightly out of focus, the stereoscopic effect is reduced or you have noticeable lens artifacts in one eye and not the other.
A number of headsets currently on the market have no IPD adjustment, or software-based IPD adjustment (with a fixed lens), neither of which give suitable optical alignment unless you are lucky enough to have the same IPD as the headset. As an example of IPD variation, in men the 5th percentile for IPD is 58.5mm, the 50th percentile is 64.0mm and the 95th percentile is 70.0mm, therefore the mean (average) is 64.0mm. Using a headset with the wrong IPD can be “interesting” to say the least, and in our opinion should not be on sale as it’s detrimental to the user and their experience of VR.
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The end goal when designing Virtual Reality equipment is “complete transparency” where it fits so well, you don’t notice you are wearing it; you simply relax into the virtual world with true immersion where you feel “present”. As we start to see higher resolution displays coming to market, the notorious “screen door effect” will diminish, and more sophisticated lens designs will reduce or eliminate optical artifacts like “god rays”, meaning that good fit will become ever more important so as to not become a barrier to true immersion.
An interesting aspect of our ability to accommodate new experiences is a psychological trait called “bohemian adaption”, where something novel soon becomes the new normal, causing us to seek further novelty as we become dissatisfied with the normal. A side effect of this is our ability to overlook flaws becomes diminished once the novelty wears off, something many VR enthusiasts have experienced once they become accustomed to their equipment and start noticing the flaws, which start breaking immersion.
The headset that had the “wow!” factor soon become irritating because it puts pressure on the forehead, their left eye always seems a little out of focus, their left-hand gets a cramp when using the controller, or they keep getting entangled in their tether. The good ergonomic design seems to reduce or eliminate these concerns, and good ergonomic design relies on good data.