Categories
Experiments

Valve ear speaker teardown

Ever wondered what was inside those neat off-ear speakers on the Valve Index?

“Balanced Mode Radiator” (BMR) ear speakers use custom drivers made by Tectonic for Valve. Valve list their audio solution as having these characteristics:-

Built-in: 37.5mm off-ear Balanced Mode Radiators (BMR), Frequency Response: 40Hz – 24KHz, Impedance: 6 Ohm, SPL: 98.96 dBSPL at 1cm.

In use onboard the Valve Index headset, the BMR ear speakers are unrivalled in terms of sound quality and sense of spatial soundstage for VR headsets, Emily Ridgway and her team at Valve certainly worked some magic here!

After experimenting with the BMR ear speakers and different audio headphones, I kept using the ear speakers as their excellent audio combined with quality of life (off-ear, on-board) was a great combination.

During the past year I did need to RMA a number of ear speakers, Steam support were very supportive and shipped them all as advanced replacement, and didn’t ask for the defective ones back. So I obtained some spares…

2 problem developed:-

1. Unwanted speaker movement. This seemed to worsen after lots of active gaming in Pistol Whip and Best Saber. Over time the ear speakers stopped holding the set position, drooping during a session or sudden movement. It appeared that the mechanism spring force degraded over time/use.

2. Vibrating. A slow developer but eventually the speaker pods started to vibrate at higher volumes or on bass hits. Not a malfunction of the driver but the physical connection between the speaker pod and speaker arm. This is felt as a looseness (slop) with light finger pressure, it’s easy to wobble the speakers pods.

Despite these problems I continued using the BMR ear speakers and gave Valve some feedback to help with further iterations.

How do they attach?

These attach to the Valve Index headset using a circular ‘pogo pin’ mounting system retained by a single torx T6 bolt through the headstrap.

Pogo pin mounting socket on Index headstrap

I decided to teardown one of my faulty BMR ear speakers to have a good look inside.

BMR Ear Speaker removed from Index, ‘Pogo Pin’ mounting system on the right
Carefully removed plastic cover (glued), I pushed it open using a flatblade screwdriver through the open slot for the height adjuster
Sliding height adjuster at minimum, power cable routing accommodates movement of height adjuster
Sliding height adjuster at maximum
Pogo pin mechanism taken apart showing pogo pin springs, bolts, sliding plate and circular pogo mounting

Looking closely at the “pogo pin” system, it’s cleverly designed using the springs to apply pressure to the pogo pins (to ensure contact with headstrap audio pads) and also allow vertical adjustment of the speaker with enough resistance to prevent unwanted movement.

Perhaps these springs are stretching over time/use, as springs do tend to stretch, to a reduced clamping force allowing the speaker pod to droop. It may be possible to tighten the small bolts to increase spring pressure, or pad the spring with steel washers to achieve the same.

The Circlip in the image above locks the speaker pod axle to the speaker arm.

This axle socket has gone sloppy (flogged out) on several of my ear speakers allowing the speaker pod to vibrate at higher volumes or during bass heavy audio. I’m unsure how this can be resolved without a different type of fitting, or perhaps a polymer bushing.

Circlip removed from axle
Speaker pod removed from arm, at this point I cut the power cables
Carefully working blade around speaker basket to break glue seal
Finally! Speaker assembly coming apart…
Wire basket removed, showing foam damper covering rear of driver unit
Wire basket removed from ear speaker pod
Thick foam damper from rear of ear speaker
Inside face of foam damper with moulding detail
BMR Ear Speaker pod stripped as far as possible, the plastic moulding was heavily glued to the front ring and resisted considerable force
Power wires to driver hanging inside speaker assembly
Detail showing driver and some type of baffling
Carefully cutting away the plastic moulding to access the driver
Driver core and baffling
Outside wire basket and diaphragm of driver
Cut apart driver showing magnet, copper coil, power leads
Close-up of coil

More information on the Valve Index audio is found in this blog article

https://immersivecomputing.org/2020/02/25/valve-index-ear-ergonomics/

Thanks for reading! Rob Cole.

Categories
Experiments

Experiments with ette…

“ette is the first of its kind finger-tracking controller. Powered by TG0’s patented technology, etee allows user to control VR without gloves, camera, or other encumbering equipment. Etee is lightweight and intuitive to use. The controller has a battery life of 8 hours that enables the user hours of time to build, explore and immerse themselves into the world of VR”

Product Description, TG0

After reading Tony’s (a.k.a Skarredghost’s) recent review of the ette controllers I was intrigued and wanted to know more – especially in light of some ergonomic concerns he raised in his article:

This was a comment I posted on his blog post after reading the review:

“Hi Tony, Great review, very detailed. The ergonomics aspect is an interesting problem, due to wide variation in hand sizing. Typically we have 3 blunt measurements:

1. length: measured from tip of the longest finger to crease under the palm.
2. breadth: measured across widest area where fingers join the palm.
3. circumference: measured around the palm of the dominant hand below the knuckles excluding the thumb.

Creating a gripped or held object to cater for the wide variation is an interesting challenge.

This challenge effect many objects whether pistol grip on weapon, household item like cutlery or cooking tool, and of course VR controller; the Valve Index controllers (Knuckles) have the ability to use clip-on Palm boosters.

I’d be interested to try the TG0 Etee controller, without getting my hands into them it’s impossible to make any valid judgement; however some physical adjustment within their structure (a clip on spacer or sliding component with locking) may be beneficial to optimise the fitting for different hands.” 

Happy XR! Cheers. Rob Cole.


Tony introduced me to TG0 who are also based in London, UK. They quickly arranged a courier delivery and within a couple of days a small box containing an Etee dev kit had arrived; many thanks to TG0.

Packaging was neat and minimalist, although I must admit I damaged the cardboard box trying to remove the controllers as their handles were very firmly wedged into the foam. I resorted to pulling the entire foam slab upwards to release them from the box, which freed the controllers but also separated the adhesive tape holding the box together.

Physical examination

The etee controllers are wonderfully simple, yet very sophisticated in terms of material technology compared to the mechanical switches and sensors we commonly see in motion controllers.

TG0’s “secret sauce” is their patented material technology used to build the sensing strips, which I understand is already used in different commercial applications – this being their first foray into motion controllers for XR.

TG0 list these as the key features of their “Etee” motion controllers:-

-Multi function TG0 thumb-pad technology

-Wireless connection

-5 finger 100 level of sensing

-6hr continue using battery life

-Gesture sensing

-Magic Trackpad with swiping, scroll, rotation and pressure sensing

-Soft silicone shore A 60 touching surface

-Weight: 75g

-Size: L136 x W60 x H30 mm

Despite coming in a little heavier than advertised at 88g vs.75g, a single Etee controller is still considerably lighter than one of my Valve Index controllers which are 197g each.

I’m also using 3D printed Valve Index ‘Palm Booster’ clip-ons, which I have to use to put controls at correct “reach” and to increase controller body “volume” to suit my medium sized hand fit, but this takes a single Index controller up to a weighty 224g.

Releasing the Palm Booster was a smart move by Valve’s designers to widen the range of hand fits possible on a single device, and many Index owners placed orders with 3D printing shops soon after Valve released all the Index mod files for free under the Creative Commons License.

From nearly a year’s experience of using “naked” Index controllers and “Palm Booster” Index controllers, the clip-on added an important tactile enhancement as the additive printing process creates a warmer, more textured surface.

This helped balance the “material mismatch” I’d experienced as a proprioceptive challenge between the soft, warm fabric strap and cold, hard plastic controller body in the weeks following the Index launch.

As well as the weight difference between the Etee and Index controllers, there is a big difference in physical size as can be seen in the side by side image below:

The Valve Index is used for comparison here as its the most advanced VR motion controller currently available to the consumer, whilst Etee offers a new approach to hand input championing a revolutionary material technology and different way of thinking.

Unlike many controllers past and present, Etee lacks physical buttons or triggers, instead providing full finger tracking across a rubberised controller body – an oval shape 26mm deep facing the palm (palmer side) and 32mm wide across the hand, combined with a large tracked thumb pad up top.

The low durometer (60a shore) controller skin has moulded vertical ribs which curve around a glowing status window, giving a soft, tactile feel with a small moulded ridge to separate the index and ring finger.

This moulded ridge protrudes 6mm from the surface, what I took to calling the “index” ridge (not to be confused with Valve Index!) to assist in locating and separating the index and ring fingers.

Controllers are marked “L” (left) and “R” (right) at the top of each handle as they are orientated specifically for each hand.

Perhaps the standout piece of the controllers is a rose gold coloured “finger bar” which provides a stiff brace for a sculpted foam cushion which is glued with adhesive tape to a channel along the inside face of the bar.

This foam bar “sandwiches” the finger against the rubber controller body, effectively capturing Etee to the hands without requiring any adjustable straps or safety lanyards which is a good “quality of life” improvement if regularly putting on and taking off.

This foam cushion is punched through with 8 triangular holes which increases its flexibility, perhaps helping to accommodate larger fingers. The foam is a relatively high density, possibly a requirement to maintain structural integrity as its only 12mm wide and 10mm deep at maximum.

The foam also has a forward extension protruding 9mm at the same vertical height as the “index” ridge on the controller skin, although rotated approximately 30 degrees around a vertical axis to the side of each ridge.

This locates the index finger of each hand and secures firmly in place by encircling that finger, whilst the remaining fingers are left “open” especially the little finger (pinky) which floats about unencumbered.

FITTING NOTES

My first quick setup attempt at fitting Etee was strange, being in a rush I pushed them on horizontally through the finger bar foam, finding a comfortable position across my “middle phalanxes”. I had tried pushing the controllers further up my fingers but found the opening between the body and foam a bit too small, I was concerned to snap or bend the finger bar if I forced them.

They felt odd but seemed to fit in some way, until both Tony and TG0 pointed out from a photo I’d emailed them, that I had them incorrectly fitted! So much for reading the instructions….

The hand anatomy image below shows the names of the 27 different bones that make up each human hand. From this image we can see the Middle Phalanx where I’d incorrectly first fitted them, and the Proximal Phalanx which was the correct location.

Image: Paul Jarrett, Murdoch Orthopaedic Clinic

TG0 advised me to fit by “sliding” the controllers vertically down over stretched hands, aiming for the foam to make contact with the proximal phalanxes of the index, middle and ring fingers. I watched the videos on their website again and it started to make more sense.

I tried fitting them again, and despite being a tight squeeze that felt sure to rip the foam off the finger bar, I finally got them on and gave my fingers a quick outstretched wiggle which felt very liberating as I now had “hands free” controllers firmly clamped in place.

I also found it a lot more comfortable to remove my wedding ring as this was being uncomfortably squashed into my ring finger during the fitting attempts.

SETUP

Setup was very easy with a USB dongle, an email I had earlier received from Tg0 contained a download link for their software.

These dev kit controllers have 3 degrees of freedom (3DoF) tracking like the older Samsung GearVR and Google Daydream headsets and remote controllers.

This means only rotational motion is tracked around a fixed location:- pitch, yaw, and roll, but not able to move forwards, backwards, side to side or up and down.

All contemporary PCVR systems and the Oculus Quest stand-alone use 6 DoF tracking for headsets and controllers; 6DoF allows movement forwards and backwards, up and down, left and right (translation in three perpendicular axes) combined with the rotation (pitch, yaw, and roll) of 3DoF systems.

I was interested to see how 3 DoF motion controllers would mesh with a 6DoF headset, in my case the Valve Index. My previous experience of using two different tracking systems together was limited to brief sessions with Lenovo’s Mirage Solo and HTC’s Vive Focus.

Both of those devices 6DoF headsets felt comfortable and immersive but compromised by a “fixed point” 3DoF controller which acted like a strange laser pointer fixed to my hip.

Is 6DoF possible?

It is possible to attach an HTC Vive Steam VR tracking puck to a special bracket, but after speaking to TG0 they advised me to wait for the new 6DoF SteamVR version of ette which is due later this year.

For the purposes of these experiments I limited myself to using the Etee visualiser whilst viewing the desktop through my Index headset, as I was more interested in the direct “hand feel” of using the controllers rather than interacting with virtual worlds.

After charging the controllers using 2 USB leads provided with the dev kit, I installed the software and took them for a test drive after starting steamVR alongside the Etee visualiser.

Calibration and rotation are easily handled through the Etee application, with a simple keyboard input starting each process, and on-screen instructions which indicate the position the controllers should be orientated against.

After getting them calibrated and setting rotation, I started my journey…

SO WHAT ARE THEY LIKE?

They feel surprisingly light in the hands, though unstable as they roll inwards towards the palm as the fingers are closed.

For quick comparison I looked at what happened when squeezing an Index controller and what happened when squeezing an Etee controller

Because Etee is clamped to the upper bones (proximal phalanxes) of the fingers rather than across the palm like index, closing my hands causes the controller to rotate as my phalanxes change angle, a large gap of 30mm before making contact with my palm.

This also causes the thumb to pivot backwards, if using the thumbpad whilst trying to close your hand! The image below shows the immediate difference in how the Etee and Index controllers are clamped to the hands.

Moving my fingers produced an immediate response in the Visualiser application and I started noticed haptic feedback loudly buzzing inside the controllers as “gestures” were made using combinations of fingers.

The most impressive aspect was their finger tracking, which I found to be very reliable once the controllers were fitted correctly and calibrated.

Individual finger tracking was almost flawless, even when lifting fingers off the body surface and placing back down in a slightly different pose; unlike my Valve Index controllers which sometimes struggle to maintain accurate per-finger tracking despite the “drum roll” recalibration and hardware reset tricks.

Etee’s pinky (little finger) tracking was especially reliable, and allowed me to finally include my little finger as a reliable participant in my experiments

Another impressive feat was their sensitivity to finger pressure, as mentioned in their literature “100 levels” per finger and its easy to understand this is no idle boast but a reflection of the precision of their material sensing technology.

This sensitivity allows controlled ramping up of pressure, and it was great fun “driving” my fingers and watching the finger levels rising from green to orange on the Visualiser.

I found the calibration process which uses outstretched hands created a strange finger input pressure if I tried to relax my hand into a neutral pose; try relaxing your arm and hand, and watch your fingers curl inwards as if holding a drink.

I tried to recalibrate from this neutral position but it caused the calibration to go a little wonky so I reset it to the outstretched fingers position again. This meant unless I kept my fingers outstretched (an unnatural pose) the input pressure rose typically on the pinky and ring fingers.

In terms of hand fit, I immediately found the foam finger bar too close to the controller body, causing my fingers to feel compressed to the point of discomfort, limiting my session time.

This sensation felt much more pronounced as Etee are securing the controller to the hand by clamping a foam block across the dorsal side (backside) of the Proximal Phalanxes.

The dorsal side of the hand is unused to pressure as its pretty much unused in everyday life, unlike the palmer side which is familiar with contact as we hold objects by using fingers to pull objects against our palms (try picking up your smartphone).

I refer back to my ergonomics article on the Valve Index controllers:-

The skin of the palmer side including the fingers is tough, thick and hairless with your fingerprints (double rows of papillae) help you grip objects as well as protect the skin from ripping.

Straight away with the Index controller I have the odd sensation of having something clamped across the back of my hand, it’s unusual as it goes against a lifetime of not having anything clamped across the back of my hand!”

The Etee controllers go one further than the Index controllers in clamping to a more sensitive part of the hand with thinner skin, and clamping using a high density foam of narrow width which is readily felt as it localises clamping pressure causing a proprioceptive challenge like Index.

Where Etee is less problematic is that the hand has soft rubber on side and foam on the other with Index having fabric on one side and hard plastic on the other which causes a material mismatch.

There wasn’t any way to adjust the position of the foam, as the bar was a fixed length to the controller body, so I turned my attention to the foam itself; thankfully this was only secured with adhesive tape so it quickly came loose.

Now with a blank finger bar, I searched through my fitting toolbox and found a number of different pads from bicycle helmets as well as foam pipe lagging of different thickness. Getting to work I trimmed different pads and stuck them in place, quickly realising the difference between ‘just too tight’ and ‘just too loose’ was critical to hold the controllers firmly in place without discomfort.

The alternative cushioning was interesting to try out, but made the controllers less stable as the material was a little too soft allowing free movement of the fingers, it needed to be a higher density like the original Etee foam cushion.

Moving further I removed the finger bars completely and tried using the controllers “naked” which was interesting, though a bit frustrating as without clamped fingers the sensitivity was all over the place making reliable inputs less frequent.

After spending a while trying the Etee controllers without their finger bars I decided to strip them down further and had a good look inside after peeling off the rubber controller body. The sensor strips were clearly visible, and some internal hardware.

Before putting the Etee controllers back together, I wanted to examine how changing the shape of the controller body would alter the hand fit so cut and taped together a larger diameter foam shape with a forward offset to create a relaxed hand pose.

Without the finger bar the controller felt like an oversized GearVR or Daydream remote and surprisingly comfortable to hold though the sensors did not register buried far underneath the foam. The big difference was that the controller did not “roll” in the palm when pulling the fingers as there was no gap with my hand “filled” by the new shape, creating a more stable grip pose.

Looking at other grips used for different sports equipment, handlebar grips on bicycles were an immediate comparison.

Round, constant diameter rubber grips are used on flat-bar sports and mountain bikes to allow the hand to move dynamically as the rider moves their body about on the bicycle, especially when standing up or sitting down. This instability of grip in the hand is what helps give a sports bicycle their agility, but at expense of stability and comfort.

In contrast, shaped ergonomic grips are commonly used for leisure bikes which are typically ridden in a seated position; another use for ergonomic grips is for riders with ulnar nerve damage whom benefit from a reduction in pressure on the wrists by having the palm fully supported.

After my quick test with the foam the solution to adjust the shape of the controller body and rubber skin would be the decision of TG0 as it would require a new design of controller (though using the same technology). Satisfied that adjusting the body shape could prove very beneficial. I refitted the rubber skins and thought more about the finger bar.

Adjustment time

I needed to create an adjustable distance finger bar; using the original high density foam piece and accommodating for different hands by moving the finger bar in or out, rather than trying to adjust a fixed distance using different thickness foam pieces…which hadn’t proven successful so far.

After sketching out the existing design and looking at the measurement I realised that creating a method of adjustment was going to be tricky due to the lack of physical space around the finger bar and body junction.

Following a number of iterations in my workshop using different cog parts (commercial off the shelf goods) like metal brackets from bicycle mudguards, plastic light fixings and different sized metric fitting bolts I finally managed to create a working prototype which actually surpassed my expectations in terms of its adjustment range.

By removing the finger bar’s attachment block (which has 2 angled keys that lock into slots on the body) I created an empty volume of space in which to fit an adjustment mechanism; 2 steel plates with oval slots to allow “infinite” sliding adjustment within its range.

A fixing bolt was captured with a knurled plastic knob with its own internal screw thread, and various bolts, nuts, grub screw used to attach the controller body to one of the steel plates, and to attach the finger bar to the other steel plate.

Finally I cleaned up the finger bar with isopropyl alcohol and firmly stuck some male velcro in place, and female velcro on the rear of the original finger bar foam so that the foam cushion could be adjusted from left to ride along the chanel of the bar – this would allow fine tuning of the foam ridge relative to the index finger on each hand.

After assembling my prototype I sent an email to TG0:

Previously I found the controller squashed my fingers which was quite uncomfortable and limited my time using them, unfortunately no way to adjust the clamping force though I tried a number of different cushions inside the finger bar (always slightly too loose or too tight). 

I quickly realised a method of adjustment was required. 

I went through many iterations to try and get this right as space was very limited whilst it needed to be easy to adjust whilst wearing, and offer “infinite” adjustment within the range of movement (clicks/notches are often just too tight or too loose).


This modification allows 3 adjustments to accommodate a wider range of hands/fingers. 

1. Distance (depth) from controller body to finger bar 

2. Angle of finger bar relative to controller

3. Lateral position of foam relative to index finger

Adjustments 1 and 2 are made using the black knurled knob which loosens and tightens a bolt, easy to do whilst wearing. 

Loosening the knob allows forward and backwards sliding movement to set the distance and adjust angle if required; tightening the knob locks the position. 

Adjustment 3 is made by repositioning the foam on the finger bar, because the foam is now velcro backed it’s easy to adjust left to right(can also swap to different shapes or materials)”.

The proof is always in using something practically, so I slipped both controllers on and started the Visualiser. For the purpose of this experiment I had modified only the left controller, as I didn’t want to risk damaging both if it didn’t work properly.

Thankfully, this was not the case, with the new adjustable left controller allowing me to find the ideal depth and best angle for the finger bar foam to maximise comfort whilst maintaining enough clamping pressure to retain the controllers in place.

This adjustment was easily done whilst wearing both controllers, with the knurled knob very easy to turn due to its vertical orientation.

The adjustment angle of the finger bar foam was limited by its square cross section, perhaps cutting a slight chamfer on each outside edge would soften its presence and allow more angle adjustment whilst providing enough flat contact against the load bearing bone to stabilise the controller.

Having the adjustable left controller and fixed right controller to compare against each other allowed easy assessment of the differences in comfort; the adjustable controller now accomodating my hand fit without squashing my fingers.

In terms of function, still very similar with the controller body rotating towards my palm every time I closed my hand.

Clamping the controllers to the proximal phalanxes will always cause this rotation but without a 6DoF version to assess using steamVR applications, I was unable to properly assess the etee controllers as virtual reality input devices.

The question of whether the mechanical switches, for example the trigger common to existing motion controllers, can be replaced by TG0 sensing technology; wasn’t something I managed to properly assess during my experiment.

The day following the completion of the adjustable left controller, the rigid plastic finger bar of the right controller snapped across its middle whilst I was removing the controller, putting an end to my experiments with Etee.

I suspect it fractured from being overloaded by my fingers being too large to accommodate, stressing the plastic over time and failing at the weakest part of the finger bar.

After speaking to TG0 they advised me the plastic was not production strength but a weaker 3D printed piece; this failure should not occur on production controllers and so my failure with the Dev kit should not be considered representative.

Immediate improvements to my adjustable concept would be a more rigid adjustment structure as the steel plates were rigid enough for my testing purposes but would benefit from being stiffer for day to day use especially for larger hand users with more strength and finger leverage.

Additionally, a “captive” bolt for the sliding adjuster plate to make it even more responsive to adjustment (the existing bolt can start turning if the knurled knob is unscrewed too far).

Finishing my time with the Etee controllers, I thought about the improvements that could be made to their ergonomic shape, and adjustment to suit a wider percentile of users.

The sensing technology itself was very impressive, and with a successful Kickstarter now backed and a SteamVR version due towards the end of the year there is a lot of potential waiting to be unlocked from this interesting product.

Thanks to TG0 for supplying this sample, I wish them luck in their developments. And thanks to you for reading! Rob Cole, immersivecomputing.org

Categories
ergonomics

Valve Index : controller ergonomics

Originally published by Skarredghost in November 2019. Edited to correct my original spelling mistakes and some images updated. All images copyright of immersivecomputing.org unless otherwise indicated.


Introduction by Tony @ SkarredGhost:

“Today I publish the second part of the interesting deep dive on the Valve Index comfort by Rob Cole. If you lost the first part, you can read it here.

Who is Rob Cole? 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. I hope you will enjoy it!”


For this second article, we will concentrate on the Index Controllers; the first article has already covered my experiments with the Index Facial Interface, whilst a forthcoming third article will cover the Index Ear Speakers.

index controllers how to improve comfort
A bunch of Valve Index Controllers fitted with 3D printed “Palm Boosters”

So how are the Index Controllers according to Valve?

Designed from the ground up to enable natural interactions, high-fidelity hand presence, and long-term comfort.

The Index Controllers

When my Valve Index arrived on launch day (28th June), the first item I removed was the right Index Controller, the headset didn’t even get a look in. 

“Knuckles” had arrived and were now in my hands…

Right Index “Knuckle” controller, freshly removed from the box

It felt reassuringly heavy (196 grams) and looked well built with a premium look, although both A/B buttons and the trigger felt a little wobbly, and perhaps a little out of place here. 

Talking of quality, despite the joysticks being a big improvement on the Vive Wand trackpad, the Index joysticks did not have the tight, precision feel of the sticks on the official gamepads for Xbox and PS4; for the high price of the Index controllers I expected better quality joysticks – something that would come back to haunt Valve?  

For weight comparison, my Oculus CV1 Touch controller weighed in a little lighter at 160 grams including 1 rechargeable battery.

The Index controllers were smaller than they had seemed in photographs but felt denser than their measured weight, indicating that there was much going on inside.

I had read it was packed full of many different sensors; looking closely I could see optical windows across the plastic shell for the Triad Semiconductor TS4112 Photodiodes that are used for the SteamVR 2.0 tracking system. According to Valve:

Each controller uses 87 sensors to track hand position, finger position, motion, and pressure to determine user intent. All of these signals, combined with fine-tuned software and algorithms, give us a better understanding of how a player is holding and using the controllers.

Joysticks and pill-shaped touchpads were around this time, finally, a much-needed step forward after the touchpad of the Vive wand became very stale following the release of Oculus’s mighty Rift CV1 Touch controller designed by Carbon.

I’m feeling prominent A and B buttons (as mentioned both a little wobbly), a guarded system button, wide trigger with a click at the end of its travel, capacitive sensors for finger tracking and force sensor for grip, the image from Valve shows the controls highlighted in yellow.

Valve index controller
Image of the Valve Index Controller with interactive areas highlighted in yellow (Image by Valve)

I quickly removed the second controller from the box and shoved both my hands into the controllers, tightened the straps with some fumbling and then violently shook my hands with my fingers open, the controllers stayed strapped in place, very cool!

Index controllers staying firmly attached to the hand

Known as “Knuckles” during their long development, these have been highly anticipated by the SteamVR community as an alternative to the HTC Vive “Wand” controllers with their simple ‘hand tool’ design and crude yet unreliable trackpads.

So what is going on here?

Some very different thinking from Valve here, to design a VR controller which does not need to be constantly held.

Each controller has a soft hand strap wrapped with a similar antimicrobial tech material as the facial interface; the controller is held by the strap (dorsal side of hand) pulling the palm (palmer side of hand) against the controller body, with the strap / controller body sandwiching the hand in place so you don’t need to constantly hold the controllers, you can rest your hands.

To help you understand, below is an image showing the four faces of the hand, “Palmer” side is your palm side and “Dorsal” back side of your hand whilst the Lateral and Medial borders are the “edges” of the hand; the Medial border would be your “karate chop” edge.  

Physical Reference system of the hand

The strap has an elasticated cord at its base mounted off a plastic turret which passes through a slot at the base of the controller, with a spring loaded button operating a clamp that locks the cord in place.

With practice, it’s easy to tighten the cord using a single finger, and release the cord with a pinch action whilst wearing the controllers.

The strap itself is also slightly elasticated, with the top terminating in a pivoting toggle which is fitted to a spring-loaded plate allowing 4 different positions relative to the controller body.  A carefully shaped piece of steel plate forms the backplate of the control face before extending out to support the tracking ring. 

The various part that compose the fitting system of the Valve Index Controllers

With the strap at resting tension I took quick measurements between the middle of the strap to the inside edge of the controller grip body and got 50mm – 45mm – 40mm – 35mm distance as I tried the 4 different settings. 

Additionally, I can see that the available volume between the strap and controller body is changing (this is not so easy to measure), with the pivot at the top allowing the angle of the strap to be altered as the strap position and tension is adjusted.

Overall, the range of adjustment is impressive and since designing and manufacturing hand controllers to suit many different hands is very difficult to implement, Valve must be congratulated for this feat.

One thing to check with your setup – due to human being’s inherent asymmetry its very common for people to have different volume sized hands (as left / right feet can be ½ size different). You may find you need your left and right strap notch positions set differently to work best – see what works best for your hands.

The long hot summer of RMAs – part 2

It’s no secret that there were some issues with the Index controllers following launch on June 28thspecifically with joysticks not always clicking or actuating in all directions.  There was perhaps some miscommunication about the reasons why, which the gaming community pointed out was ahem…wrong…holding their Rift, PS4 and Xbox controllers as evidence.

valve index controllers rma
Returning controllers…thanks to Valve for free return shipping

Both my launch pair and my replacement pair had no click nor actuation when pushed forwards and backwards with the left controller joystick, or left and right with the right controller joystick. The RMA process was relatively painless though it took 2 weeks each time from sending them back to receiving a new pair.

So I bought an Xbox One controller and thoroughly enjoyed spending some time doing seated VR with games like Assetto Corsa, House of the Dying Sun, Hellblade: Senua’s Sacrifice and Aircar which had just been released as an updated version free on Steam (previously this was used through Revive and my Oculus library).

xbox controller vr
We always think about VR controllers, but sometimes also a gamepad can offer some enjoyable virtual experiences

Thankfully the replacement pair (pair #3) did not have the joystick problem and a number of Index owners on the subreddit started reporting that later production date controllers have been shipping without the misfunctioning joysticks.

Some people buying full kits reported that they found their controllers were from earlier manufacturing dates and required an RMA to replace with more recently manufactured controller stock. There is even a spreadsheet on Reddit where people receiving replacements are invited to log the date of manufacturing and report any issues.

However there are other issues now being reported with the more recent controllers of joysticks developing “drift” and loud squeaking triggers.  I felt lucky, for a while…

but after a month of light use (6-8 hours a week) pair #3 developed a loud squeaking in the right trigger, loud enough to be heard in VR, and a wobbling left joystick that is laggy when using free locomotion in VR or even just trying to teleport around Steam VR home environments.

Checking if new Index controller joysticks click or not?

Valve has supported my latest RMA request with an “advanced replacement” pair on Index controllers, so I didn’t have the usual 2 week turn around. These come from a warehouse in the Netherlands, which is where Indices for European customers are stored.

4th time lucky perhaps? Time will tell, back to the findings…

SOMETHING FEELS ODD THOUGH…

Index Controllers are strapped to hands rather than held as normal, this in itself immediately presented two “challenges” for my hands.

First, the dorsal side of the hand is unused to pressure as its pretty much unused in everyday life, unlike the palmer side which is familiar with contact as we hold objects by using fingers to pull objects against our palms (try picking up your smartphone).

The skin of the palmer side including the fingers is tough, thick and hairless with your fingerprints (double rows of papillae) help you grip objects as well as protect the skin from ripping.

If I wear a pair of gloves, these provide a cushion between my palm and whatever it is I am holding, gripping or pushing against – gloves also make light contact with the dorsal side, lateral and medial borders (sides of hand) as well as the palmar side – “wrapping” the hand in an envelope of fabric, that with a well-fitted glove can become almost “transparent” in use. 

Straight away with the Index controller I have the odd sensation of having something clamped across the back of my hand, it’s unusual as it goes against a lifetime of not having anything clamped across the back of my hand! 

These sensations do tend to fade over time as the body becomes accustomed to new sensations but it’s certainly an odd sensation and initially feels more intrusive than holding a HTC Vive Wand or the Oculus CV1 Touch controller (often held as the “Gold standard” for VR controller design).

vive wand vs oculus touch
Vive Wand compared with the Rift CV1 Touch controller

The second challenge was caused by a material mismatch – the soft fabric strap against the dorsal side which felt weird (from contact) but not uncomfortable unless overtightened; and the hard plastic body of the controller against the palmer side which felt normal (used to contact) but a bit uncomfortable.

The tighter the strap was pulled (increasing tension) the more the mismatch was felt, like a hard plastic bar being pulled against my palm rather than a comfortable controller. The controller body felt a little too narrow with not enough width at the top where the index finger and middle finger sit.

The hard plastic also proved slippery when getting hot and sweaty playing fast paced games,  allowing the hand to move around despite being strapped tightly in place – some texture to the plastic or an alternative rubber-like material choice could have helped.  

The strange sensations of the Index controllers almost felt like Sensory Processing Disorder, my hands didn’t feel like my hands in VR or that my hands were holding VR controllers, generally a bit odd perhaps causing a proprioception issue.

Proprioception, or kinesthesia, is the sense that lets us perceive the location, movement, and action of parts of the body. It encompasses a complex of sensations, including perception of joint position and movement, muscle force, and effort. These sensations arise from signals sensor receptors in the muscle, skin, and joints, and from central signals related to motor output. Proprioception enables us to judge limb movements and positions, force, heaviness, stiffness, and viscosity. It combines with other senses to locate external objects relative to the body and contributes to body image. Proprioception is closely tied to the control of movement.

Definition of proprioception, Encyclopedia of Neuroscience

Proprioception relating to body image is very interesting, here is a simple experiment:

Try closing your eyes, move your arms above your head; now try touching the end of your nose with your right index finger – I’d be very surprised if you miss?

Another test, place a piece of paper on a table in front of you, sit and then draw an “X” in the middle of the paper.

Take a look at the X, close your eyes, raise your pen arm up and then bring it back down to where you think the X will be, make a mark, open your eyes, try again several times and see how your accuracy improves, this is proprioception recalibration on the fly!

We maintain a surprisingly accurate body image based on the rich wealth of proprioception generated as we inhabit our bodies, which can be leveraged with interesting results when using immersive computing platforms like Virtual Reality. 

However, if things feel “off” then it’s immersion-breaking because it causes an irritation that is eventually impossible to ignore, like a stone in your shoe that needs to be removed because it’s distracting your running. Something weird was going on with the “Knuckles”.

Is the controller body a little small?

Strapping my hands back into the Index controllers, I spent a considerable amount of time trying the 4 different positions and varying the strap tension in each position. With fine-tuning, it was possible to get an effective working position where the controller stayed in place without the back of my hand facing uncomfortable pressure.

This then led to a strange situation where I was having problems reaching the controls with my hands strapped correctly in place – my thumb was too far forward relative to the joystick, to get my thumb located correctly I had to pull it back at an uncomfortable angle, or loosen the strap and slide my hand back slightly, which then meant the controllers weren’t strapped securely to my hand!

valve index controllers comfort
Users must decide between comfort of the hand and correct thumb position…

Despite the less than ideal fit, I carried on using them and managed to get the finger tracking to work effectively but I found the “reach” for the joystick, trackpad, and buttons continued to be uncomfortable.

The Trackpad

The trackpad has changed, it used to be a large circle on the Vive wand, but has been reduced to much smaller, pill-shaped design on the Index.

A look back at the 3+ year development of the Knuckle controllers show the joystick was a relatively recent addition with the earlier development units having a large trackpad like that on the Vive wand.

It’s been reported that Valve did not have a liking for free locomotion in VR, preferring teleport, but have since come around to the free locomotion used in many popular games, hence the inclusion of a joystick whilst keeping a trackpad.

The inclusion of both control systems (pad and joystick) is noticeable because the axis of my thumb does not seem to fall naturally on one or the other. With the right controller, I need to deflect my thumb slightly to the left to use the touchpad and deflect my thumb considerably more to the right to use the joystick.

It felt like both were “off-axis” and it was a little uncomfortable. As I finding the controller a little small and my thumb too far forward, this deflection was probably more extreme than with a correctly fitting (larger?) controller body. 

Deflection of thumb from its natural axis

The trackpad itself is no technical slouch, but due to its limited size and “pill” shape it can be awkward to use with any accuracy especially for people with larger hands and bigger fingers.  

I would prefer an Index controller with no trackpad and just a high quality joystick on the correct axis to naturally fall in-line with my thumb, perhaps a revision for the next generation of controllers? (thanks Valve!)

Can the fit be adjusted?

As a “sample size” person (medium everything, including medium-size gloves) I’m certainly not an outlier in terms of size; this left me wondering if the Index controllers did not fit my somewhat average-sized hands, what about everyone else? 

After looking at the controllers for far too long one evening trying to figure it out, it dawned on me that increasing grip volume on the palmer side (hard plastic body of the controller) could improve the fit of my Index controllers.

Using the same principle of offering fitting choice, for example “narrow” and “wide” facial interfaces for the original HTC Vive, perhaps there was a way to adjust the volume of the controller body to suit different sized hands?

I tried wrapping the body of the controller with masking tape and then strips of card which increased the grip volume, and also increased the reach to the controls giving a more natural thumb position with less deflection to reach the joystick. 

Despite the loss of finger tracking during my crude hack, it showed a volume adjustment “skin” or clip-on spacer could work.

A crude experiment to improve the comfort of Valve Index controllers
The “Boosters” arrive

Soon there is encouraging news that Valve are releasing a set of CAD files for the Index under the Creative Commons License, and these include “Palm Boosters” as well as the “Frunk” dimensions and sensor exclusion zone maps.

This forward thinking by Valve gave a gift to the modding community with an invitation for people to hack the technology for their own purposes. Their previous collabaration with HTC, the Vive, was openly designed to be hacked and received many “frankenmods” as well as official upgrades like the Vive DAS. 

I quickly download all the Index files and use my .stl viewer to closely inspect the Palm Boosters, a very simple but effective design with intricate support and weight reduction latticework on the inside.  

valve index controllers booster
CAD Image of the booster

The 3D printing shops were soon busy printing Palm Boosters, I used Printlix in Romania through Etsy.com, and chose Boosters in a very bright yellow color so I wouldn’t lose them in my VR room. Surprisingly they only cost £22.38 in PLA (polylactic acid) including shipping with a estimated 3-5 business days before arrival.

The boosters soon arrived. Examining them closely, I could see they were well printed and had a snug fit when clipped into the controller body. They were a little crudely finished around the cut-out for the lanyard release button, which could be easily finished with some wet and dry grit paper so I left that for later (maybe one day…)

Valve Index Controllers and yellow boosters

The “boosted” surface facing the palm of the hand has a slightly rough texture from the additive printing process, which is very useful as it provides a slightly warmer feeling and more tactile surface increasing my hand feel and hand control; truly a good thing for active gaming where the slippery body of the controller was not ideal.

The difference in fit was immediate, I took some measurements across the middle of the controller body and got 36mm wide / 35mm deep for the ‘naked’ controllers and 40mm wide / 40mm deep with the Palm boosters fitted.

Valve Index controllers with boosters
Valve Index controllers with boosters installed

Pushing my hands into the controllers, I start setting them up again and I noticed less strap tension was required, and my thumb was now falling into a more natural position for the joystick, trackpad and A/B buttons.  The amount of deflection to reach the touchpad  and joystick is lessened as my thumb is now further away.

The thumb felt much more comfortable with the boosters

The reduction in strap pressure and warmer feeling material have changed the feeling of being tightly strapped to something narrow, hard and obviously plastic, to a more warm sensation of a comfortable contact without edge pressure.

The big improvement of fitting and more comfortable contact, along with time spent using the controllers has reduced my “proprioception challenge” to a level where the Index controllers are feeling good in my hands.

Without any doubt, the Boosters have transformed the fit of my Index controllers, and Valve should be congratulated for releasing the CAD file to enable this important final fitting piece of the controller puzzle to be completed.

I liked my boosters so much, I got a spare pair from Etsy.com and Printlix a few weeks later, this time in “mystic green”…

Classier mystic green boosters

One consideration, and not one I needed to test myself as the Valve Palm Boosters worked great for my medium-sized hands, is whether someone with larger hands would benefit from a “larger volume” Palm Booster design?

It should be relatively easy to manipulate the CAD file and increase the volume on the Palmer side to suit larger hands, and this is something I would encourage any large-handed people to try out as a solution for Index controller fitting issues.  

Ultimately a method of 3D scanning the hand and creating a custom Booster, per hand to accommodate our inherent asymmetry, would be the ultimate ergonomic modification for these interesting hand controllers.

It is arguable that they are so important for fitting medium-sized hands, and as some on the /r/valveindex subreddit have reported, even for fitting smaller hands –  a question then for Valve is whether the Palm Boosters should come standard in the box with the Index controllers

What about the games then?

Whilst I’m not here to list which game worked or didn’t work with the Index controllers, I did find some games simply refused to load or work with my Index, whilst some only worked after messing about with controller bindings.

It seems that all the VR applications on Steam are listed as being compatible with “Index” whilst this is blatantly not the case, it’s down to developers to update their applications. 

At times Steam refused to save my bindings, but the binding system seems to be working much better now, and there are lots of community bindings often better than those from official developers. 

I did find the finger tracking to be little more than a visual gimmick in some titles, whilst a few really took the concept and ran it with. At times the Index controllers behaved and felt just like using a Rift CV1 Touch controller, which is no bad thing!

“Aperture Hand Labs” and “Moondust” were already installed on my PC, and perfect examples to showcase the Index Controllers finger tracking and force grip sensors.

Aperture Hands Lab demo by Cloudhead Games and Valve

Playing rock, paper, scissors with a maniacal robot was great fun, with an awesome Aperture vibe of the Portal variety, a great experience for Valve, Portal and Half Life fans no doubt!

Moondust had some very cool gravity manipulation and hand grenades, rocks to crush and radio control moon buggies to drive about on the lunar surface; whilst I didn’t really get anything from the rocket kit assembly experience.

Technical demo Moondust

More importantly, Valve updated THE LAB with its “Hands-On” update!

The Index update brought finger tracking, enhanced audio and physics to The Lab, easily my favorite VR application to date and one that at 144hz and 250% supersampling using my RTX2080Ti has an unreal, “skin tingling” feeling of presence.

More easter eggs abound with a Knuckles development kit box waiting to be knocked off an overhead rafter with your bow and arrow. This update to The Lab’s physics is brilliantly demonstrated by your hand controllers haptic interactions with your canine robot companion, producing a metallic bumping feeling as you run your hand across his body.

The update to The Lab is very timely because it shows where Valve’s technology is moving and it runs beautifully at 144hz; I look forward to many more hours playing the mini-games or just hanging out drawing bad pictures on the whiteboard and shooting the warehouse workers, or adjusting my playspace to find hidden spaces 😉

A Valve Index controllers’ box inside The Lab

These applications showed the real potential of the Index controllers, it’s now down to developers to implement proper Index support in their existing applications and for any new applications coming to Steam. 

Oculus games using Revive on Index ran very well, seeming to treat the Index controllers just like Touch controllers, with Robo Recall being a standout with the grip feature on Index letting me equip my side holstered guns with better accuracy than on Touch.

Some games surprised me in that the Index controllers didn’t feel as good in the hands as other controllers due to the style of gameplay, the first being Beat Saber.

Beat Saber grip?

I found with Beat Saber that the hand straps massively hindered my slashing actions by strapping my hands to the swords instead of allowing me to flick my wrists like with Wands and Touch. 

I slipped my hands out of the straps by backing them completely off with the strap on setting #4 to give maximum space which felt better.

I then found the boosters didn’t play nicely with unstrapped hands as they moved slightly sometimes creaking so I removed them – Beat Saber has ridiculously fast controller movements so it’s not surprising a “clipped on” piece could feel loose during frantic gameplay. 

Then I tried moving my hands further down the controller body until I found a very natural perch around the intersection with the tracking ring which felt like the Pommel (base) of a sword – perfect for Beat Saber.

how to valve index controllers beat saber
How the Index Controllers felt the best when playing Beat Saber

It was much more comfortable, allowed super-quick wrist flicking and never felt like I would lose a controller despite my “energetic” attempts at what could be called dancing in Elixia by Mord Fustang. It’s probably a good thing that VR generally takes place alone in dark rooms…

This change of hand position on the Index controller gave a feeling more like the classic Vive Wand, which is arguably still a great “tool” for Beat Saber with a physical shape that feels like holding a sword or saber.

The other genre of game I found didn’t work so well strapped into the Index controllers was my favorite “In Death” the brutal Rogue-like first-person bow shooter. I also tried other shooting games which required fast trigger work such as classic “Space Pirate Trainer” and found a similar issue.

Bow Grip?

Strapped in, my left hand (bow hand) felt less precise when aiming at distance or headshots, and my right hand (arrow notching and teleport arrow) felt slightly restricted by the strap on the right controller.

The strap runs across the knuckle and tendon for my trigger finger, causing a slight feeling of drag.

If you work your trigger finger and watch the backside of your hand, notice all the movement going on under the skin up the index finger, across the index knuckle and across the hand into the wrist as the tendons move under the skin.

I like to play In Death with a fast, aggressive playstyle and actually found the Index controllers a step back after some blistering runs using the Touch controllers on the Rift CV1.

So I slipped the straps and found a great “loose” setup with a Bow hand pose stabilizing the aim, and my trigger hand unimpeded by strap pressure. Using the loose controllers also helped with faster reactions when getting jumped or mass spawnings of bad guys when teleporting into a location.

Best bow grip I found for “In Death”

Space Pirate Trainer also felt much better unstrapped, with a faster trigger finger action and easier over-the-shoulder grab for the shield.

The great thing to realize is you don’t always have to be strapped in, and you may find better hand positions for different games or experiences. You should have received lanyards with your controllers, and I’d advise using them if playing unstrapped as there is potential for a controller to part company with your hand when unstrapped with expensive or painful consequences!

Xbox One Controller

Some VR games require a gamepad controller, whilst others might just play better with one – a great example was “Aircar” where you fly around a city in a BladeRunner-esque flying vehicle. It was a favourite on Oculus, and has recently been updated for Index and added to the Steam store still as a free download.

aircar valve index
The amazing Aircar experience…free on SteamVR. I’d happily pay good money for this!

Whilst Aircar was perfectly playable with the Index controllers, apart from some issues with the “Turbo” button and being able to access in game settings, it felt considerably more natural using the Xbox controller which gave the physical feel of a flight “yoke” as you’d use in a light aircraft.

Trying to hold the Index controllers next to each to simulate the yoke felt like an effort, whilst the Xbox controller just melted into my hands. This is similar to trying to play shooters like Onward and Pavlov using motion controllers without a gun stock, i’ts not great!

Aircar is a super chilled experience, so anything that can increase immersion is a great thing and this instance the Index controllers felt redundant with the Xbox controller proving a much better hand fit and the higher quality joysticks giving a smoother, more precise flight feel.

The Take Away?

The take away from my Index controller experiments:

  • Exciting new SteamVR 2.0 input device
  • Interesting new interaction methods that need support from developers
  • Aperture Hands Lab and Moondust are great showcases for the controllers
  • Excellent tracking and no occlusion in bow or gun games
  • Uncomfortable “out the box” with fitting and material challenges
  • Boosters made a big difference even for medium-sized hands
  • Larger volume Boosters potentially a good fix for people with larger sized hands
  • Custom printed Boosters could unlock more fitting potential
  • Don’t always have to be strapped in, try moving your hands around.
  • Gamepad controllers still work better for some applications
  • Some applications won’t work without rebinding or modding, some not all. 
  • Make sure you buy new directly from Valve as you may need warranty support
  • Would like to see trackpads ditched and higher quality joysticks in a future version
  • Would like to see controllers come with Boosters in the box

It’s really down to developers to now implement Index controller support where appropriate, which of course depends on how many consumers purchase Index compared to the less expensive and easier to use Oculus Rift S and soon-to-tethered Quest.

Around the time this article gets published, 46,000 Index are reported to be sold since the Index launch on 28th and Index has already made a noticeable dent in the VR headset surveys on Steam which indicates a healthy level of activity.  

Hopefully we will see the best examples of Index controller support and amazing new interaction in Valve’s new VR title when it finally releases – said to be late 2019 by Valve, but of course subject as ever to Valvetime – they’ll release it when it’s done!

Thanks for reading! Rob Cole, immersivecomputing

Categories
ergonomics

Valve Index : Headset Ergonomics

valve index ergonomics

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.

valve index box
Valve Index full kit in neat cardboard box

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…

Valve box full kit
Lots of spares thanks to Steam support sorting my 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.

two valve index
Advanced replacement for my headset meant I had indices for a week

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.

Ratchet strap came from factory with offset spacing causing headset to sit twisted on head

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:-

  1. Index Facial interface
  2. Index Controllers
  3. 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

Time to dive into valve’s new Index PCVR headset

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”.

valve index facial interface
Valve Index facial interfaces

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:

 Face Gasket

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.

valve index rubber spacer
Rubber spacer provided with the Valve Index

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. 

valve index sweet spot
In headset lens shot showing lens off axis (left) and on axis (right), demonstrating the importance of a good fit when using the Index

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.

A good fit is very important when using a VR headset

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. 

valve index face mask gap
The gap is very visible between foreground and cushion

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.

Uncanny valley effect in action (image by Creepy Girl)

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.

VR Cover’s soft fabric Index cover (image by VR Cover)

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..

Valve Index CAD
Example of CAD file released by Valve (Image by Valve)

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. 

valve index ergonomics
Experiments with Velcro proved a wider facial interface could work

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. 

FACIAL INTERFACE STRIP DOWN image
Valve Index facial interface strip down

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.

3D printed wide facial interface base by Ninja Prototype

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.

valve index ergonomics
Gluing magnets on the new face mask

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. 

Making the mask…velcro fitting

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. 

Wide facemask on the Valve Index

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.

No annoying gap anymore, a good fit for my 59cm head

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.

Modifying the face cushion to increase visible FOV

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”.

magnets valve index fit
Magnet stacking for fine tuning of Index face gasket

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.

valve index wide face mask
Valve Index with wide face cushion about to be worn

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).

Glorious presence in the Valve Index

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 standard Index interface (top) and the modded one, note the big difference in radius

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. 

Sweat inside the Valve Index

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…)”

Categories
ergonomics

The importance of ergonomics in VR

Originally published by Skarredghost in August 2018. Edited to correct my original spelling errors and some images updated.


Introduction by Tony @ Skarredghost

“I always say that most of my readers know VR far better than me. For sure this is the case of Rob Cole, that you surely know because he comments a lot on this and other VR blogs

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 immersivecomputing (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.

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.

I found the topic very interesting, so I asked Rob to write something for me about it… and so, here you are with a very interesting post on VR ergonomics. Have a nice read!”


I’m at the technology store today in my local shopping mall because I want to get a new VR headset.

The latest model by “Virtual Dream” was released a few weeks ago, but I’ve had to wait until the end of the month for payday. I approach the sales assistant manning Virtual Dream’s in-store concession, he sees me coming and greets me with a friendly “Good morning!”

He’s already noticed I’m looking keenly at the new headset inside the display case to the right of his booth, and knows what I’m going to ask next.

“Have you got time to do a fitting?” I excitedly blurt out, and he nods enthusiastically before replying, “That would be a pleasure, however, it will take about twenty minutes to print your face mask if that works for you?” I tell him that’s ideal as I need to get some breakfast, so I’ll come back and pick up my headset once I’ve eaten. 

He asks how I’d like to pay, and I swipe my phone across his terminal, taking a third of my pay cheque. “Okay, if you can come around to the left side of my booth we can get you measured up”, he asks, “You might have seen this online but it’s pretty cool to try out in person” he adds.

On the counter of his booth is a small camera attached to a circular support frame, with a padded chin rest. He gestures for me to lean forward, and after I place my chin on the rest, he lowers the frame over the top of my head. “Please keep as still as possible, and make sure to keep your eyes closed” he suggests, before pressing a button on the rear of the camera. 

I hear a gentle whirring as the camera moves around my head, and less than ten seconds later, my 3D scan is captured, “That’s all done, we got a great capture here. Okay, your circumference is 58 cm so we recommend a medium, and your head shape is ideal for the Y-style harness”.

He picks up a tablet computer from the counter, and makes a few keypresses before turning back to me, “That’s all done, if you want to come back in about twenty minutes I’ll have it boxed and ready to collect.” As I walk away to find my breakfast, I hear the 3D printer starting to do its work.

“I returned my ******* because of the discomfort and bought a ****. The ******* didn’t fit properly and hurt my forehead after 30 min. Really wanted to keep the ******* but if I can’t wear it, there’s no point”.

“The *** was super uncomfortable for me and gave me a headache, whilst the original **** was very comfortable for me, especially once I got the ***”.

“I literally couldn’t go more than half an hour on the ****** without getting a nasty headache, so I can’t say if you will like either, you should try and demo one first before buying?”

“The **** just made my head hurt, and I found the controllers too small (I have large hands), but the **** fitted great and the controllers were way more comfortable.”

These are all real responses on a virtual reality forum after posters have asked: “Which headset is best?”…only the names have been changed to protect the innocent headsets. 

One person recommended headset X because they found it fitted them well, whilst headset Y was a poor fit that they found painful to use during longer gaming sessions.

A second person has replied with an answer that is the opposite; they thought headset Y was fantastic and spent hours using it, whilst headset X had them quickly reaching for the pain killers. So who is right?

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.

virtual reality headsets ergonomics

Other examples are scuba diving masks or full-face motorcycle helmets, although neither of these have 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.

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 space suits 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.

Image result for nasa vr
Astronaut training at Nasa used VR (image NASA)

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.

Oculus Rift CV1 has been used by many different people

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 artefacts in one eye and not the other.

virtual reality headsets ergonomics
One Vive Focus worn by three different people

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 95th percentile is 70.0mm, therefore the mean (average) is 64.0mm.

Using a headset with incorrect IPD can be “interesting” to say the least, and in my opinion why fixed IPD headsets should not be on sale as it’s detrimental to the user and their experience of VR unless lucky enough to have a similiar IPD.

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 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. Good ergonomic design seems to reduce or eliminate these concerns, and good ergonomic design relies on good data.

virtual reality headsets ergonomics
One person wearing Rift CV1, PSVR and Daydream

When designing equipment, an “Ergonomist” (human factors design specialist) will look at anthropometric data. 

To suit the general population we’d look at a range from the 5th percentiles to the 95th percentiles of the dataset, which will then suit 90 percent of the population, and accept that people outside of these percentiles will not be catered for by that design.

This anthropometric data has been gained by measuring huge numbers of people over a number of decades through large studies by many organizations including those in the medical profession and the military.

As an example, a functional arm reach for “5 percentile female” is 73.5cm whilst for “95 percentile male” is 94.2cm. This difference in reach of over 20 centimeters is one example of the wide range seen in the human population, and variations are also present in craniofacial measurements.

As the old saying goes “You can please some of the people some of the time, but not all of the people all of the time”.

The aim is to please as many people as possible unless you are aiming your product at a specific group of people using a specific dataset, as there are different sets of anthropometric data to target different groups of consumers.

Some examples would be general datasets for Men, Women, Adults, Children, or more specific datasets, for example, Caucasian or Asian. Appropriate anthropometric data is a critical ingredient for good ergonomic design, but data can be limited for smaller population groups which have not been widely studied.

virtual reality headsets ergonomics
Each headset has its own design of facial interface

Companies like Oakley manufacture their sunglasses in “Regular” fit and “Asian” fit, as do a number of bicycle helmet manufacturers.

You will also see different “foot forms” used when designing shoes for a Germanic foot, Celtic foot or Greek foot, just to name a few of the different foot shapes found across the human population.

The companies that manufacture VR headsets choose a particular dataset (head model) when designing their headset, and will make design choices or compromises to try and suit the largest possible user base of their target market.

If you fall outside of this dataset, or have unusual features (as many of us actually do), you may find your headset is uncomfortable, slightly blurry or even painful to wear. This explains why a VR headset designed for the Asian consumer is often a poor fit for a Western consumer unless you actually better suit the fit of an Asian headset.

You can now start to understand why there are different opinions on VR headsets, and why it’s difficult to recommend a particular VR headset to a friend, colleague or stranger on the internet based on your own experience of wearing that headset.

A problem with the different “fits” that the current headsets have, is that you may want to choose a particular model based on its technical features, access to its content, or wish to support that company, but you might try or buy that headset only to find it doesn’t fit you properly.

Modifying Daydream to improve comfort and stability

Within each headset design, there is only a little that can be done to adjust fit, apart from some of the radical modifications people make. These tend to be “band-aid” fixes that only partially resolve fit issues to make that headset into something that can be tolerated, other fixes involve severe modifications that void the warranty which is less than ideal on an expensive headset that is only 2 months old. And sometimes the official upgrades can make the fit worse, for example, some Vive users bought the DAS only to find it much less comfortable than the original soft harness.

virtual reality headsets ergonomics
Three models of HTC Vive, three different form factors

You might have heard the word “ergonomics” when people discuss virtual reality headsets, such as “that headset had poor ergonomics!”. It’s a slight misuse of the word, as the definition of ergonomics is:-

“Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system […] in order to optimize human well-being and overall system performance” (International Ergonomics Association)”.

Ergonomics is also known as “biotechnology”, “human engineering” or “human factors engineering” and has played an important role since the introduction of desktop computing in the office, where workers often spend hours doing repetitive tasks with a limited range of movement.

An Ergonomist is a specialist in the applied science of equipment design, intended to maximize productivity by reducing operator fatigue and discomfort.

As we move into the realm of immersive computing, the focus of the Ergonomist will shift from the desktop computing environment to the immersive computing environment which we access through virtual and augmented reality headsets.

This in itself presents a new set of challenges, ranging from equipment design to user interface design, and physical movement limitations inside virtual environments.

So what can be done to ensure headsets (and hand controllers, which we have not even mentioned) are comfortable? It’s a tricky problem to solve, as during the early adoption of consumer VR the development budgets are limited by the small size of the market.

This doesn’t leave much room to spend money on tackling difficult ergonomic challenges by offering a headset model with different “fits”, or providing much in the way of customizable or modular headset designs.

Improving comfort for the forehead

Magic Leap’s first AR headset has just come to market and shows some interesting thinking as its’ offered in two sizes, as well as each size coming with a “fit kit” offering a number of shaped pieces for the nose and the head padding.

This AR headset is different to VR headsets in that the waveguide technology does not allow for moveable displays to adjust IPD, so they’ve had to offer 2 headset sizes to accommodate users with a smaller IPD range and users with a larger IPD range.

However, if we run with this thinking, it could be possible for a manufacturer of VR headsets to offer different sizes, just as bicycle helmets are often available in small, medium and large sizes.

The current “one size fits all” model of the headset is a bad compromise, just as “one size fits all” cycle helmets rarely satisfy anyone, resulting in a loose fit or pressure points as the adjustment system cannot accommodate such a wide range of heads.

Each individual size of bicycle helmet has further adjustment using a ratcheting, radial harness system to really fine-tune the sizing; a medium cycle helmet will usually adjust from 55cm-59cm, as well as offering 3 volume settings using a rear vertical adjuster.

In addition to sizing options for VR headsets, different style of headset harnesses could attach to the same headset base to accommodate users with different shaped heads, especially to suit the occipital bone (the pointy ridge at the back of your head).

An additional design solution is to offer a user-specific, custom facial interface (face cushion). A custom facial interface helps accommodate the asymmetry that is found in our faces, and the direct influence this has on the optical presentation when wearing a headset, and user comfort.

Current headsets are designed so that the face is centred within the headset, and the IPD adjustment works off this premise so that an IPD set at 64mm has equal spacing of 32mm left and 32mm right.

But what happens when your face is not centred within the headset because of your facial asymmetry, and your left eye is actually further from your nose (34mm) than your right eye (30mm)?

Take an image of your face, and draw a vertical line straight down the centre, then measure the position (width) of each eye relative to this centre. Repeat the exercise by drawing a horizontal line across your face, and measure the position (height) of each eye relative to this line, the results are often surprising.

Further analysis shows variations between the depth of each eye within its socket (orbit), the volume of the cheekbones (zygomatic or malar bone), the shape of the forehead (frontal bone) around the brows and reports of 19 different nose shapes.

We also see optical variations with eye dominance or eye-specific refractive errors requiring specific adjustments (it’s not ideal to wear glasses inside a headset).

These physical variations can be accommodated by a custom face cushion, whilst optical variations can be catered for fitted prescription lenses and automatic IPD adjustment using eye tracking systems to cater for each eye individually. We are starting to see new prototype headsets coming to market with these automatic optical adjustments, which is very encouraging.

virtual reality headsets ergonomics
Hacking the Vive to customize it to the user’s face shape

Currently the aftermarket face cushions you can purchase for headsets like the Rift and Vive are offered in different thicknesses and types of material, but follow the same concept of the OE (original equipment) face cushions of a symmetrical shape, equally spaced for left and right.

These don’t allow any asymmetrical accommodation, which means one side may be more comfortable than the other, this is seen in “witness marks” as the bony facial structures compress the padding used in the cushion. What is required is a method of supplying a face cushion which properly fits that individual’s face, and ensures they align correctly with the optical display.

One solution is the emerging technology of 3D face scanning, for example, the Bellus3D Face Camera Pro which is plugged into an Android smartphone. This combines 2 proprietary state-of-the-art technologies that measure 500,000 3D points on the subject’s face creating a very accurate high-resolution face model in seconds.

We could take this face model and integrate it with a design model of the headset to generate a data file for a custom face cushion base. This could be 3D printed and layered with self-wicking, antibacterial materials to provide a skin-sensitive layer to prevent any irritation, reducing facial stress and heat build up. A layered approach with breathable memory foam  could ensure a supremely comfortable fit!

The same technology can also be used to scan the head to assist in selecting the correct size of the headset and correct style of headset harness to suit the head shape. Once installed in the headset, the custom face cushion and correct headset harness will give the user a truly customized fit addressing their craniofacial asymmetries, whilst eye tracking systems adjust IPD for asymmetry and depth focus on a per eye basis.

As described in my fictional story at the start of this article, in the near future we could see virtual reality and augmented reality headsets offering an individually customized fit that we believe is required to truly get the best from the experience.

virtual reality headsets ergonomics
A customized face cushion is a solution to improve the comfort of every VR user

VR enthusiasts often focus on technical specifications, obsessing over resolution, pixels-per-degree, refresh rates, tracking systems…perhaps forgetting the most important element of the equation is the human interface. As one colleague commented last year, the clue is in the name “headset”, a “set” you wear on your head.

As consumers, we can purchase custom footbeds for running and cycling shoes and heat molded ski boots, which have been successfully sold through retail outlets for a number of years. With some forward thinking this business model can be incorporated into headset sales, with consumers only needing a “one-time” capture which could be applied to whichever headset brand they purchase in the future, similar to the data your optician holds on your prescription.

We should look forward to the immense benefits to be gained from customizing our immersive computing headsets, to provide the best comfort and optimum optical presentation so we can relax in our virtual worlds, at least until its time for a bathroom break!

virtual reality headsets ergonomics
virtual reality headsets ergonomics
How the VR headset of the future should be to have great ergonomics

I really want to thank Rob for this very interesting post. I agree with him that now maybe it is a bit too early for VR companies to care about this since they are mostly focused in actually selling the devices… because the user base is still quite little. But later on, in the future, I think that it is room for these important improvements in ergonomics so that the user experience inside VR can be optimal. People that spend lots of hours in VR will be happy because of this.

Tony @ Skarredghost