Originally published by Skarredghost in October 2019. Edited to correct my original spelling errors and some images updated. All images copyright of immersivecomputing.org unless otherwise stated.
Introduction by Tony @ Skarredghost:
“If you are interested in ergonomics in virtual reality, today is your lucky day. I host a guest post by Rob Cole, that will show you his journey in making his Valve Index more ergonomic, modding both the headset and the controllers so that they can accommodate perfectly the shape of his head and hands.
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 centre of his experiments and analysis. This post is the result of such kind of experimentations on the Valve Index headset.”
June 28th was a key date this year for a group of Virtual Reality enthusiasts who received on launch day, the first delivery of the new “Valve Index” PCVR system.
As a member of this small group, who against the odds had managed to secure a pre-order on May 1st, mine arrived at 12.31 pm on the 28th leaving me with the afternoon for installation and my first session.
The excitement of opening a new VR kit cannot be underplayed, it’s like receiving something magical, but I kept cool and took some unboxing photographs to preserve the moment for posterity before the packaging got tatty and the controllers bruised from striking walls.
By early afternoon it was installed, base stations bolted high up, covering a useful 3.0 x 2.8m play space, generous for a domestic installation in London.
In preparation for Index’s arrival I’d already installed the “Aperture Hand Lab” and “Moon dust” applications so I could try out the finger tracking of the Index “Knuckles” controllers, which were plugged into cellphone wall chargers to bring them up to full charge.
It was now time to take a deep dive into Valve’s Index to see what it was all about and test out the 144hz mode, which I was confident could be properly explored by my PCVR rig using its overclocked 8086K processor and 2080Ti graphics card.
A long hot summer of RMA’s…
This article has been a while coming….2 headsets, 3 pairs of controllers and a right ear speaker since launch meant more time in meat space than I’d recommend to any VR enthusiast.
Despite some frustration over time wasted and trips to courier depots, I gained a cool collection of Index boxes and unavailable spare parts including extra cabling and a spare facial interface; for one rare week I had 2 Index headsets (Indices!) sitting on my desk.
It was also uncharacteristically warm in the UK this Summer, so when Index was fully working it was confined to early 6-8am sessions before the day heated up.
New product launches can be difficult with new components from suppliers not meeting agreed specifications, or new production line processes where small assembly mistakes can have big usability or quality of life impacts on the end user, sometimes requiring replacement through the RMA process.
As a small example, my launch headset arrived with the headset harness offset to one side due to improper assembly, which caused it to sit skewed on my head as the offset gap just got larger the further the headband was opened.
After some communication with Valve, it was advised to force the ratchet mechanism by hand to try and balance the strap, which thankfully worked and did not seem to cause any permanent damage to the plastic internals.
The phrase “Early adopters always pay” has been proven right once again, but as active support is being provided (albeit slowly at times and with different results) and Valve’s manufacturing partners in the USA and China improve their Quality Assurance, we can move forward.
Downtime with reality can prove fruitful, so during the long hot summer of RMA’s I dove into the ergonomics and looked at the 3 key areas that were bothering me during my VR sessions:-
- Index Facial interface
- Index Controllers
- Index Ear Speakers
For this first article, we will concentrate on the Index Facial Interface; a later article will cover the Index Controllers and Index Ear Speakers.
Index Facial interface
Index arrived with a single, removable facial interface, fitted to match a full–width pad glued inside the rear of the headset harness. It looked great, with a premium fabric outer and a comfortable foam inner; something that pre-release reviewers had spoken about favourably.
In Valve’s own words,“The Face Gasket for the Valve Index Headset is made with anti-microbial fabric that is soft on the skin and ergonomically designed to distribute pressure evenly”.
The magnet attachment system was a neat idea, though perhaps a little understrength as it was too easy to accidentally knock the facial interface from the headset; the first time this happened to me caused a moment of panic that the magnet may have scratched the right lens, thankfully it hadn’t.
There wasn’t a different width interface or a spare interface provided, which puzzled me as the HTC Vive (a Valve collaboration) had shipped with both narrow and wide facial interfaces – the “wide” really a regular fit and the narrow for people with narrow faces.
Interestingly, some digging around on the internet by Steam user “BOLL” showed a now archived Valve product webpage for the Index headset from 1st April listing:
|2 Face Gaskets (narrow and wide)|
By April 30th he noticed the webpage had been edited to remove any mention of narrow and wide, leaving:
Not sure what happened during this period, if there were plans for narrow and wide that got cancelled, but at launch Index shipped with just one Face Gasket (or Facial Interface, if you prefer).
Instead, there was a rear cushion provided in the box for smaller heads, a basic foam rubber piece which seemed at odds with the anti-microbial fabric used for the facial interface and rear harness pad. Perhaps a lastminute addition, and a welcome one to provide more fitting options, but also likely to trap heat and moisture against the occipital bone (rear of head) raising the in-headset temperature.
I’d always used the wide facial interface on the Vive as I’d tried the narrow interface before without any success when I got my first Vive in early 2016. People have different width and shape faces so the provision of narrow and wide facial interfaces made sense to anyone with a basic understanding of ergonomics.
Looking closely, Index’s interface seemed to be slightly wider than the Vive narrow but considerably narrower than the Vive wide.
Having also used my Vive with thin 6mm face cushions and now struggling to fit my face properly into the somewhat narrow interface of the Index, I wasn’t impressed with the field of view which felt more like my Rift CV1.
The omission of a wide facial interface for Index seemed very strange considering the obvious effort Valve had spent improving the headset’s overall ergonomics and how important the facial interface is for correct fitting especially for such a precise headset.
I soon found that the “sweet spot” (optimum eye position, relative to lens) was similar to the Vive in that it was relatively small – demanding a precise headset fit to align properly.
The incredible clarity that had been talked about in reviews is something I could see by removing the facial interface and holding the headset close to my face. This allowed me to determine the issue was not caused by the display system (I got great clarity with this method) but the physical interference of the narrower facial interface.
Fitting is best done with the harness lifted up and the headset held loosely against the face with one hand so the sweet spot for each eye can be aligned before holding the headset in place whilst tightening the top strap (weight bearing) and rear harness (stability) using the other hand.
As my previous article on ergonomics explained, the facial interface is the primary physical interface for a Virtual Reality headset, the secondary physical interface is the harness.
The headset’s facial interface and harness should ideally support the optimum position for the user in that headset and then “fade into the background” by not applying undue pressure nor cause skin irritation.
VR headsets require a good craniofacial fit to provide visual clarity and stereoscopy, for headset stability (especially during movement) and long session user comfort.
The aim when designing wearable VR equipment is to make it ‘transparent’ to the user; remove any physiological barriers to immersion to enable users to achieve a strong sense of presence on a repeatable basis.
Unfortunately, in my case the facial interface just wasn’t compatible with my face, I was finding it difficult to get my eyes into the right position causing optical aberrations and mild eye strain.
The need for constant adjustment and overall discomfort was dramatically reducing my enjoyment of Index to the point where I considered selling it, but before taking any drastic action I started by looking carefully again at the facial interface to see what I could do.
After removing the facial interface from the headset, I held it against my face (as if wearing the headset) and noticed a sizeable gap between my forehead and the face cushion, large enough to put my middle finger in the gap.
I could reduce this gap by gently bending the plastic base plate against my head, but when the facial interface was clipped back into the headset there was no such movement.
Tightening the harness just pulled my face deeper against the foam without finding adequate support, I could feel the headset moving slightly sideways as the foam further deformed trying to accommodate the mismatch with my face.
One side effect was a black shape (display edge) noticeably present in my left eye but not in my right eye, to prevent this intrusion I had to dial the eye relief further out, further reducing the field of view.
I could get the position almost right by really forcing the headset’s position on my face and manipulating the headset harness but any tether movement would cause a shift unless clamped so hard it started causing craniofacial discomfort (i.e. sore face and headache).
With a slightly larger left cheek (zygomatic) bone than my right, I noticed that every time I tightened the headset it moved left, moving my left eye further off the sweet spot.
All humans beings display asymmetry which is perfectly normal, in fact there are few if any humans with perfect symmetry, which is why computer generated characters with symmetrical faces have an eerie “uncanny valley” effect.
From my ergonomics work with performance athletes, I have not yet met anyone with perfect symmetry as all of my clients required adjustments to their equipment to accommodate their natural asymmetry in an effort to improve performance and minimise the risk of injury.
We are all asymmetrical whether it’s our hands or feet being slightly different sizes, the very common trait of a leg length discrepancy, a larger ear or a dominant eye. In everyday life, we learn to accommodate these discrepancies and rarely consider them (you might find one shoe is tighter than the other) but in more specialist situations like fitting a VR headset it can become a problem depending on the amount of asymmetry.
My accommodation for this width mismatch is typical, there is a tendency to offset to the dominant side whether it‘s a VR headset or bicycle saddle – with a wider facial interface my asymmetry is present but does not cause such a radical shift in position.
Additionally, as a “sample size” person (medium everything) I’m certainly not an outlier in terms of size; this left me wondering if the Index’s interface did not fit my somewhat average sized face, what about everyone else?
Searching the internet, nothing wider was yet available from the after market companies as Index had just been launched. The only product I could find coming soon was VR Cover’s soft cover, which just wraps over the existing Index facial interface actually reducing the width.
I reached out to Valve and was told “Steam support does not have any information on when or if a new gasket will be made available.”
I reached out to VR Cover and was told: “The team is still exploring several solutions for the Valve Index, so I’m unable to confirm if this is being developed. However, I’ve passed your suggestion on to them.”
So I continue using the Index as various RMA play out, but continue to struggle with my fit, “chasing the sweet spot” with moments of success followed by constant adjustment.
I was seeing huge potential in the Index marred by frustration at my failure to find a good fit and the face cushion was starting to degrade with foam compression and ripples appearing in the fabric, not surprising considering the facial mismatch I’m asking it to try and accommodate.
A wide face cushion emerges
Soon though, there is news of CAD files for Index being released by Valve, which includes a facial interface base design suitable for 3D printing. Excitement grows, files are released, the modding community is energised. ‘Boosters’ are also featured in the file dump, but more on those later..
Within days, I find a modified face cushion base which has been widened and released by Anonymous Hermit under the Creative Commons license.
It’s on Thingiverse and I quickly used my smartphone to try some 3D printing suppliers in the UK with the cheapest quoting nearly £250 (!!) but then discover Ninja Prototype who have a longer lead time but only want $33 including shipping from their Chinese print shop; it’s looking promising, there is hope yet!
RMA continues for controllers with joysticks not clicking in all directions so I purchase an Xbox controller and spend VR time driving cars way too fast in Assetto Corsa, and hearing voices in my head during the mindbending trip that is Hellblade : Senua’s Sacrifice.
This period of seated VR proves useful to start experimenting more with the fit without the constant tug of a headset cable threatening to pull the headset out of alignment. I try using it without the face cushion by stacking strips of soft Velcro fabric; crude but very promising as it confirms the headset can easily cater for a wider face with the right interface. I also have some ‘wow’ moments of optical clarity which confirm the potential.
During the Steam summer sale, I learn Valve is giving me a load of credit on Steam at the end of the sale as a reward for the Index purchase. I get a free pack of Index face cushions and some VR games… thanks Mr. Gabe!
Now with 4 face cushions (1 left from a headset RMA) I am free to experiment, so I quickly strip the worn original down to see what’s inside, interesting to see no doubt, and I salvage the nose gasket from it as I have just received notification my 3D print is arriving this week from Ninja Prototype.
Previous experience modifying headsets includes the original HTC Vive and Google’s original Daydream, so I check my Amazon account and quickly find some old orders for aftermarket face cushions and industrial strength Velcro I can use to secure the cushion to the 3D printed plastic base.
Ninja Prototype deliver on time providing me with a very stealthy looking 3D printed facial interface base.
I source slightly stronger N42 Neodymium magnets from Amazon and use an epoxy adhesive to bond each magnet firmly to its mounting turret, making sure they are leveled and centred. After the epoxy has cured I lift the print to the headset and it snaps into place with a satisfying click; the magnetic attachment is working as intended and now more resistant to accidental knocks. I carefully glue the nose gasket poached from the original Index facial interface in place using a special “gel” Cyanoacrylate which does not run.
Turning my attention to the facial interface base, I wipe the surface with isopropyl alcohol, letting it evaporate in preparation for fixing the male-pattern Velcro that will be used to attach the aftermarket face cushion to the plastic base. Disposable nitrile workshop gloves are used at all times to prevent any skin oil or grease contaminating the bonding surfaces.
The first tricky part is cutting the Velcro to fit, which will require using as few pieces as possible to minimize any side shear from peeling the Velcro off when adjusting or removing the face cushion. Normally, the Velcro is a single piece, machine die-stamped using a cutting pattern, but I don’t have that luxury.
To generate a cutting pattern I stick masking tape on the rear of the Velcro’s adhesive tape cover, so I can hold the Velcro against the base and use it as a template to draw a pencil outline. Adjusting for height, I eyeball it and carefully trim the Velcro with sharp scissors and check by placing each piece against the base.
I end up with 4 pieces, long strips top and bottom, small pieces left and right, I radius the corners to remove sharp corners which can get snagged and lifted when opening and closing Velcro attachments.
The second tricky part is actually fitting the face cushion to the Velcro on the plastic base, its hard to centre and mount with equal spacing around the perimeter. Normally, facial interfaces and face cushions have a locating key to help with this, but we are freestyling here...a couple of attempts later it’s looking good.
It’s now time for the “moment of truth” so I click the wide face cushion into place, give the lenses a quick clean, loosen the headset harness and lift the headset onto my face, just one word slips out of my mouth: “Wow!”
Immediate thought is I’m back in a Vive but with more vertical FOV and slightly more horizontal, crisp edge to edge clarity and much higher resolution. The lenses and the display feel very different to the Vive Pro, it’s an impressive upgrade no doubt. I remove my new facial interface and do the “gap test” again, this time it‘s a great fit.
I hold the headset to my face with my left hand, before adjusting the harness; I try moving the headset around to find the right alignment to give each eye the best presentation. I carefully set the IPD and manipulate the eye relief adjuster until it looks and feels just right, using a variety of different scenes, the Real O Virtual test background and left/right eye checks.
Just as with my Vive, I need to rotate the headset slightly clockwise (from my POV) to raise the lens sweet spot to meet my left eye, like many humans my asymmetry includes one eye (my left) that sits higher than the other eye (right) on my face.
With these adjustments set right, I notice the black shape is now missing from my left eye, and only appears equally on the edges of left and right eyes when winding the eye relief so far inwards the lens edges actually touch my eyebrows, so I wind out 2 clicks until there is no contact.
To increase the FOV without the lenses hitting my eyebrows, I look at my face cushion, it’s slightly obscuring the edges of the eye box, so I try repositioning it on the plastic base. The HTC Vive had a smaller eye box so it‘s not surprising the after market cushion is not a perfect match for the Index’s larger plastic base.
I resort to cutting up an aftermarket face cushion, and manage to carefully fit it as 3 pieces, with some Velcro tape securing the cutting gaps on the rear of each piece.
Now it’s opened up the eye box, and I am getting the full-fat FOV that the Index can offer. It’ss also extremely comfortable with an equal level of gentle pressure across my face even when tightened. The headset has a stability I have not had before, requiring less tension on the harness to stay in place. The headset now offers good support from having the correct interface and has become much more comfortable with no need for constant adjustment.
I also quickly realise with the magnet mounting system that fine tuning of the fit is possible to further address asymmetry so I experiment with “stacking magnets”.
In addition to the strap pivot on the headset block, it’s also possible to also change the display plane angle relative to the eyeballs with this method as well as the rotation of the interface relative to the face. After many experiments, I found that 2 magnets on the top right and lower right mounts provides a very interesting result “cleaning up” the display in my right eye by taking away a fine slight fuzziness – I suspect caused by my eyes sitting at different depths in their orbits (eye sockets).
Its a very interesting process and adds a big advantage to Index for modders, it allows some adaption of asymmetry without resorting to expensive 3D scanning of the face to custom print a personal facial interface.
Firing up SteamVR I spend hours in Valve’s “The Lab” at 144hz and with super-sampling cranked up to 2.5 (the advantage of using a 2080Ti GPU): I’m just marvelling at the clarity, small details and unreal sense of presence. Whilst kneeling to look at the sides of the arcade cabinet, the robot companion dog runs up to me and I am so startled I fall over (thankfully onto the rubber floor in my VR room).
Speaking of presence, with physical discomfort removed and the optical system now aligned, I soon realise the “secret sauce” Valve has baked into Index is the high frame rate and ultra low persistence; the virtual world has never looked and felt so real, with noticeable jumps between 90hz, 120hz and 144hz.
The Index is doing a great job of tricking my subconscious “lizard” brain that this is real, and I’m feeling a level of presence I’ve never felt in any other VR headset, it‘s hard to describe, it feels incredibly vivid both spatially and temporally.
Perhaps Norman Chan from Tested said it best, “I didn’t know you could get so much more out of 120, 144 hertz and feeling more present until I used the Index. With 120 and 144 hertz its like I’ve downed 2 cans of Coke and I’m hyper aware”.
My job here is done, the wider facial interface works and is letting me exploit Index to its true potential and revel in strong feelings of presence. However, I know from previous experience that cutting up face cushions is not a long term solution as they tend to degrade from having unsealed edges and cut foam, loose fabric, etc.
The wide option certainly works, but the next step is producing a commercial version that can withstand daily use. Another angle would be a “gamer” version with slightly firmer padding and more moisture resistance designed to stand up to the rigours of long session, active room scale gaming and allow for quick cleaning.
For now I’ll keep using my wide prototype, enjoying my Index and experimenting with alternative face cushions. As can be seen in the image below with the eye relief wound all the way inwards, I now have equal balance between left and right sides of my face as witnessed by the equally placed sweat contact marks on the top of the lens surrounds.
This success of this interesting experiment (which I encourage other Index owners to try, even as a stop gap measure) leads to a simple question aimed at the manufacturers, specifically Valve but also the aftermarket companies:
“Please can you make a wider facial interface for the Index?”
Final note: Community reactions
Since starting to write this article, comments have appeared from Index users on the Valve Index Subreddit which demonstrates the demand: (of course, I have removed the usernames):
-“They also need to release wide face gaskets a.s.a.p…many users are out of luck with the stock gasket and have to print their own”.
-“My face can’t take any more”.
-“This is a very strange omission from the Index HMD. I mean the Vive had it. Does Valve think that all of the wide-face consumers don’t buy the Index? It really limits the fov due to keeping the lenses further away”.
-“Valve is expecting 3rd parts solutions to cover this, no one is even saying they are working on one.”
-“I have seven, wish they fit my face tho :/”
Thanks for reading! Rob Cole, immersive_computing
“I hope you enjoyed this deep dive in VR ergonomics. If it is the case, stay tuned for the second episode of the series and feel free to contact Rob to talk with him about ergonomics in VR! (Or contact me asking me to put you in touch with him…)”