Valve Index: A good fit? Part 2 – Analyzing and improving the comfort of Knuckles controllers

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!

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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.

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 (28^th 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…

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.

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!

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.  

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. 

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 28^th, specifically 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.

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).

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.

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.

4^th 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).

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!

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. 

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.

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.  

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…)

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.

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 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”…

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.

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.

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 😉

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.

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.

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.

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 28^th 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!

(Header image by Valve)