VR Locomotion

With the strong launch of Oculus Quest 2 (Facebook/Oculus has collected a record number of monthly active users over the last 7 weeks), the adoption of VR devices is growing like mushrooms after the rain. More than 100 VR games are already making over $1 million, and the business VR projects are progressing at breakneck speed. The VR is here and the number of apps, titles, and games is only going to rise.

The biggest proponent for this growth has been an affordable price along with the hardware upgrades, including tracking systems, resolution, comfort, and even incorporating new technologies such as hand tracking, but VR applications have definitely improved their experiences, with better standards for interactions, locomotion, and UX.

What is VR Locomotion

By definition, locomotion is the ability to move from one place to another in physical space. It derives from the Latin origin words locō (place) and mōtiō (movement).

Virtual reality locomotion is the technology that enables the movement of the avatar or user (in this case you in the first person) through the entire virtual world, using only a small real-world space. Locomotion is one of the pillars of a great VR experience.

Why is VR Locomotion Important

In the resurgence of AR/VR since 2015 when the hardware and technology allowed more dabbling and creating VR worlds achieving immersiveness was (and still is) the biggest goal.

VR replaces your reality with digitally constructed worlds. The problem is, even if the digital environment is tricking your brain in one way, the other senses are being disrupted by the “glitches in the matrix”.

Your inner ear functionality includes the sense of presence in the room, balance, and body direction, and stability in movement. To avoid sickness and nausea, the movement in VR should mimic the movement in physical space.

That is how we achieve realism, right?

However, how do you “walk” in VR if you’re in a seated experience? Even sophisticated omnidirectional treadmills (i.e. the platform OmniVR) are only just barely trying to imitate the real world.

In 2019, the University of California user study “A User Experience Study of Locomotion Design in Virtual Reality Between Adult and Minor Users”, the researchers found out that physical body movement that mirrors real-world movement exclusively is the least preferred by participants; both adults and minors.

Most of the artificial movement in VR is achieved through hand-held controllers that are part of the headset package like Quest 2, Oculus Rift, HTC Vive, and others.

According to Oculus for Developers guidelines recommendations you should take into account several elements when developing and designing experience using artificial locomotion:

• Acceleration — fast, unexpected movements lead to discomfort or even nausea. Special attention should be applied to torso and head movement.
• Speed — to be in the human perception golden range, Oculus recommends speeds of human locomotion: between 1.4 m/s and 3 m/s.
• Direction and Positional Tracking — with a motion controller setup, the user sets the range of space (guardian mode). Designers/developers must understand that backward movement and lateral movements are rare.
• User Control — Let users control the motion as much as possible/ This is extremely important when it comes to gameplay and enjoyment.
• Visual Quality — the quality of the visual is crucial as well. There’s a thin line between quality and performance. Rapid movements such as head bobbing may break the immersive experience.

VR Locomotion Techniques

There are several methods on how to transport the user through the environment. Each method comes with its set of benefits and challenges.

Locomotion techniques have been tested and perfected for some time, aiming for seamless and user-friendly navigation in a variety of virtual environments, and we now classify them like so:

Room-Scale Based

This approach utilizes only the player’s physical movement in the real-world space, and so, the applications must be designed around this constraint. Beat Saber is a good example of this, where your only movements are for dancing and dodging those pesky walls.

Motion-Based

This technique uses some extra sensors, which for now aren’t included with the major headsets, to detect some kind of physical movement, and translate it into VR movement.

Controller-Based

For generations, gamers have been controlling their characters using a trackpad or thumbstick, and using this same method on VR applications seems only logical, but the perception of moving in the virtual world, while remaining stationary in the real world, may cause motion sickness, or more specifically, something called “Vestibular Mismatch”.

So, in order to make this kind of locomotion possible, some extra techniques had to be added for it to work, like reducing the field of view while moving in VR, which limits the amount of detail noticed by the player, and in turn, decreases the triggers for Vestibular Mismatch.

Teleportation Based

This is the only non-continuous locomotion technique, meaning when the player teleports, they are instantaneously repositioned to the target location, with no in-betweens. The target location is selected by the player by aiming with the controller, and sometimes they can also select a facing direction for the teleport.

Like the controller-based technique, a raw implementation of this locomotion also has some drawbacks, suddenly changing the player position, with no context at all, will leave her completely lost, and so, there are a few variations for this technique.

Blink

In this variation, upon selecting the target position, the player view fades out, they are relocated to the virtual world, and finally, the vision fades back in. Almost as if the player blinked and voilà! They are in a new location.

Dash

The blink locomotion is by far the most used, but it can hinder the player immersion, and for that, there is the dash variation. In this version, instead of blinking into a different location, the player is rushed there at super speed.

For this technique, we must be really mindful of the vestibular mismatch problem, as this sudden movement would definitely trigger it. Raw Data deals with this by adding some dash animation effects that serve as an anchor for the player, much like a car cockpit would.