Legless in VR: the Problem of Locomotion

Legless Avatars: image by CNBC, story “Within a decade you may be working with a digital twin” — Dec 2020

Whether you’re an old VR hand or one of the legions of newbies discovering the technology during this time of lockdown and tele-whatevering, you’ve probably discovered a couple of things about VR.

One is: VR is just plain awesome. There is nothing in our previous computing experience like being able to look around freely and naturally, have full depth perception, and “touch” and manipulate game objects with our hands (either directly or via controllers). It’s a whole new world, and it puts a big dumb grin on most of our faces. [I think affordable VR is one of those historical inflection points in UI technology — like the first windowing OS, or the first touchscreen pocket device — when the world changes; but that’s a topic for another essay.]

The next thing you notice — if you’re me anyway — is that your avatar in most VR sims and games has no legs! The amazing realism of VR environments — the incredible immersion compared to “pancake” (flat-screen) gaming — stops at the hips (where your hands come to rest). You have no legs. There are no sensors on your feet. You can’t walk, kick a ball, or dance.

Well, actually, in many VR worlds you can walk around, even if your feet aren’t being tracked. Relative motion is well-scaled, head movement is perfectly natural, and it feels great — incredibly immersive. But there’s one serious gotcha: most of us have playspaces small enough that you can’t walk very far before you hit a boundary. And even those few of us who can afford to dedicate a sizable room to our VR habit still can’t walk through Half Life: Alyx! The bigger and more challenging the virtual world, the more the playspace boundaries constrain our ability to explore it.

In our VR dreams, we walk freely as far as we like through magical worlds of adventure, exploration, and virtual tourism. But in our present VR reality, we run into the furniture.

The game devs have thought about this a lot and come to a convergence, if not a perfect consensus; if you want to get around in the VR world, there are two industry-standard solutions. One is to use one of your controller mini-joysticks (usually the non-dominant hand) to “glide” or zoom around — kind of like driving a drone, except the drone is you-in-VR. The other is to use one of the buttons on a controller to throw an illuminated target spot out in front of you, then teleport to that target location.

So gliding and teleportation are the prevailing methods of locomotion in VR worlds today. And that solves the problem of limited playspace. While standing or sitting still inside your boundary, you can explore expansive worlds.

Sadly, both of these methods are disappointing. Some people feel a little (sometimes a lot) motion-sick, when skittering around like an air hockey puck while their physical body remains at rest; and teleportation is just so darned immersion-breaking, like reminding you every few seconds that you’re in a game/sim. Neither method engages your body realistically, in the way that VR otherwise engages your hands and arms to grab, throw, climb, fight, swim and so on, plus your head and neck to look all around you. Tracking head position allows you to bend, crouch, and stand on tiptoe realistically… but you can’t walk or run.

Some folks resort to walking or running in place while using the joysticks to glide around; this can reduce the puke factor quite a bit. It provides the natural head-bobbing view of your surroundings that says “I am walking” to your brain, as well as the familiar rhythm of stepping with feet and legs. But really, you still have to use a joystick to move and steer; and you’re trying to match your pace to the gliding motion, instead of moving normally at a speed determined by your pace. Natural-feeling locomotion in VR just isn’t there yet.

At the fringes of every industry are people trying to solve the hard problems by unconventional means. The VR locomotion problem is no exception. In one camp there are people working on captive running rigs: physical devices that let you run and walk freely while tethering your physical body in place. These rigs tend to be expensive and bulky, of course; but they’re darned ingenious.

The most exotic and (to me) droolworthy examples are the fabulous Omnideck and the only slightly less fabulous Infinadeck. These are large, complicated and definitely not-for-the-home-market gizmos that use active positional compensation to keep the player centered on an x-y treadmill surface no matter how fast s/he runs or walks. These are the VR floors of our dreams, that allow infinite locomotion in any direction. Run, walk, turn corners, no problem. But the price tag? Don’t even think about it. For enterprise clients only.

Further down the price chain we can find “skating in a bowl” slidemill variants like the Kat VR product line or the Virtuix Omni. But the thing about slidemills, as Packet39 blog ruefully admitted back in 2018, is that they don’t feel like walking

Maybe these slidemill issues will get worked out, but for the moment what you’re really doing is cross-country skiing inside the dished top of a steel drum… it can be a workout, but it ain’t walking.

The folks behind StriderVR have a different idea: a modest sized platform that permits omnidirectional walking in VR, but not running, fast side stepping, or jumping. While this might be a fine solution for virtual tourism or mild fitness workouts, it seems a little underspecified for active gaming. It’s also rather narrow in its target market (requires a Kinect 2) and currently in prototype, not production.

Continuing down the line from “most to least costly” we find a half-body VR suit (lower body only) called WalkOVR which uses 5 strap-on sensors plus a SteamVR driver layer to add leg/foot movement into your gameplay. Dunno about you, but having to “get dressed” for several minutes before playtime sounds a bit intimidating, and those straps don’t look very comfortable. Maybe for hardcore gamers only; and in any case, it’s presently “out of stock.”

Lower still in the price chain are clever but sketchy hacks like rocker boards that let you pump your feet while sitting in a chair (hardly immersive), or Cybershoes that work similarly, requiring a special carpet/mat for its wheeled shoes to “skate” on. Or the VRgo gaming chair which lets you tilt and spin to move in VR. Basically, these gizmos allow you to “walk and run” … while sitting. Which I guess is better than nothing, but it’s not the immersion level that I dream of. I love being able to play standing up, and also getting exercise while gaming.

The other line of approach to the Legless Problem is software; there are various hacks, patches and demos of ways to use your body motion (or a couple of extra trackers for feet) to get the feeling of natural walking and running in VR. The appeal of the software solution is obvious: it doesn’t involve a large additional investment in bulky equipment, you’re not strapped or tethered to a frame, and you’re not forced to make unnatural motions that then get mapped into walking.

Natural Locomotion is another Steam driver/patch that activates joystick navigation by means of arm-swinging or the addition of additional “lighthouse” trackers to your feet. Some gamers like arm-swinging as a locomotion method, but obviously you can’t be aiming your longbow or charging with swords ready to strike, while swinging your arms. Setting up additional traditional trackers and integrating them into your Steam gaming setup rather weakens the standalone, portable appeal of the Quest 2 with its inside-out tracking; and it’s complicated, not for the average user.

Freedom Locomotion VR by Huge Robot (George Kong) is a free demo app, not a patch or driver for existing games; it’s the first one I spent any serious time with and I was so delighted with it that I wrote a raving Steam review. But wonderful as FLVR is, it’s “the most exciting proof of concept demo I’ve seen for VR” — and not a finished product that you can use for gaming.

VRocker is a Steam game controller patch that uses head-bobbing motion to activate the standard twin-stick gliding locomotion mechanism. By bouncing gently in place, or rocking from foot to foot, or walking/running in place, you can move around. The patch is very tunable to your personal preferences; many people have found it enjoyable, especially with action/combat games involving run/crouch/stalk tactics. The demo is fairly convincing, too. It doesn’t work with all games — and it needs tuning to create a custom profile for each game for each user.

I ended up settling into VRocker as my software locomotion solution. I’ve been using it mostly with SkyrimVR, a game that just cries out for real walking and running. Not having to (unnaturally) use buttons and sticks to move around is more powerful than you can imagine if you have not yet experienced it! This is how I want to move through VR open worlds. The immersion is massively enhanced when your body is moving more or less naturally in synch with your actions in the game.

The VRocker developer is active and maintains a presence on a dedicated Discord. We’ve had many a long discussion about tuning options, UI, features, etc. VRocker has many loyal and enthusiastic users, mostly because of the following features: you can divorce gaze direction from movement, so you can walk while looking from side to side, without weaving like a drunk; you can tune it for your own movement style; it has per-game profiles; it leaves your hands (mostly) free to interact in the game.

I have a few minor bones to pick with VRocker (discussions continue on Discord!). It doesn’t perform smoothly at very low speeds, or at least I have not yet figured out how to tune it for low speeds. Jogging is much easier than walking, and it’s very difficult to “creep” cautiously. It also uses LH controller pointing direction for steering, which means your left hand is tied up and you can’t do two handed combat or archery while walking. Because it’s head-bob oriented, it sometimes responds to sudden head movements when you are standing still — so you may lurch forward suddenly if startled by a noise that makes you whip your head around. In crowded scenes or when going into combat, I switch back to joystick movement (sad, but true).

One of the coolest things about VRocker with SkyrimVR is that it works on horseback. You can hold your hands in a nearly-natural “reins” position and do gentle rhythmic partial squats, a motion rather like posting on a real horse — and your horse will trot forward. The immersion is remarkable. There are some issues when turning corners (keeping your avatar properly aligned with the saddle) but in general, VRocker and horses are a match made in heaven. My SkyrimVR playtime has now become a gentle workout, as I walk and jog in place and exercise my core and quads when riding.

If VRocker can solve the “pussyfoot” slow walk and the leisurely amble, it is just about perfect for infinite foot (or horse!) travel in any large open world that uses standard joystick smooth movement. (It works perfectly over Virtual Desktop as well as Link, for all you Quest 2 users.)

It’s always easy to be utterly wrong about any technological development. But I venture to predict that hardware “infinite VR walking” solutions are wrong-headed. The problem is very expensive to solve via electromechanical gizmos, and the gizmos that work are (thus far) weighty monsters inappropriate for the home market.

Even the cream of the unaffordable XY treadmill crop are still more like walking on ice than real walking; inertia and hysteresis are really hard to overcome. But it’s very easy to run in place, and very easy to convince your brain that you’re actually moving in the VR environment. Maintaining your position in the playspace is a minor issue (I’ve seen some interesting setups with ceiling-mounted leashes!) and much easier to solve than the very complex physics and mechanics of running on active ballraces or XY conveyor belts.

Development continues, as VR enthusiasts and the industry try to figure out how to “get our legs under us” again. Who knows which solution will prevail, but I’m really hoping for something as much as possible like VRocker and Freedom Locomotion to become industry-standard (like gamepads) and embedded in all commercial VR headsets within a couple of years.

The immersive euphoria of running at a realistic speed through a realistic VR landscape is hard to convey in words, but it has made a profound impression on me; it leaves me with a lingering sadness every time I have to teleport to get around in an otherwise deeply engaging VR game or experience (Hello, The Room VR!)

I invite comments and discussion; if you’ve been very satisfied with solutions that I dismissed, please share your experience. If you know of other nifty ways to walk or run in VR, please let me know about them.

[This article was updated in late Feb 2021 to incorporate my favourable experiences with VRocker.]

Retired; ex-software engineer. Paleo-feminist. Sailor. Arduino tinkerer. Enviro. Libertarian Socialist (Anarcho-Syndicalist, kinda). Writer. Altermondialiste.

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