What Is “Presence” in VR, and Why Is it So Important?

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The great breakthrough of modern virtual reality was the ability to create “presence”, a feeling of being in a different place than you are. Achieving presence has been a long and difficult process, but it’s the secret sauce that makes modern VR magical.

VR presence defined

You may not think too much about it (which is a good thing) but do think about the place where you are now. Whether at your desk, in a park, or some other place that you find yourself in on a particular day, you don’t ask if you are really there, do you? You feel physically present and accept reality on a subconscious level.

This is exactly what VR creators want to achieve with the experiences they create. For VR to be convincing, your brain has to accept the virtual world as real. At least to the extent that you’re actually there, not that the things you see are necessarily real, which is another discussion.

“Presence” is difficult to put into words, but it is unmistakable as an experience. It’s like looking at a 3D image with the “magic eye” that suddenly becomes sharp. It is the result of subconscious processes that are part of the way your senses and your brain construct your reality.

Our brain constructs reality

This raises an interesting fact about how we perceive the real world. That said, we don’t really do that. The world that you perceive around you and the associated feeling of being present is not the real world at all. It sure is based on the real world, but what you perceive is a reconstruction of reality. They don’t even live in real time! Since sensory processing takes time, your perceptions are always a few milliseconds behind what actually happened in the world around you.

It’s not a one-way process either. Our previous experience and knowledge of the world influence how things look to us. A brain has a limited capacity so it always tries to take short cuts, including falsifying the details of what we perceive based on what we have seen or experienced before.

We can even lose our sense of presence in real life, which is one of the main symptoms in psychology dissociation – a detachment from reality.

However, this is good news for VR developers as we know that our brain creates a sense of presence based on what our sense organs are currently reporting and our past expectations and experiences. So in theory, all you have to do is give the brain the right sensory inputs and design your VR experience so that it doesn’t violate the user’s expectations of reality. Well, at least not by accident.

How VR makes your brain feel present

A woman wears a VR headset to play a winter sports game.
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It sounds easy on paper, but the real challenge was figuring out what exactly your brain needs before evoking that sense of presence. The pioneering work that companies like Oculus have done, as well as years of academic research into VR and related fields, have resulted in more or less a formula for presence.

It turns out you don’t have to 100% replicate the real world to get the brain to feel presence. When a few key requirements are met, you can feel a sense of presence with an affordable headset (like the Quest 2) and relatively simple graphics.

First of all, there is the quality of the tracking. That is, how the VR software tracks the physical position of your body in virtual space. The tracking must take place in all axes of the 3D space. Also known as “6DoF” or six degrees of freedom. Tracking accuracy must be within 1mm of your true position in 3D space. There can be no “jitter” in which the VR world jumps between slightly different positions and the image wobbles. A stable image is essential. You also need this exact tracking in a relatively large and comfortable space.

Perhaps one of the most important requirements for presence is low latency. In other words, the VR world has to react to your movements so quickly that it feels like it is in real time. According to John Carmack, a key technologist in the development of modern VR, 20 ms of latency between motion and photons is the dividing line for presence. This means that from the point where you initiate a movement to the place where the photons that reflect that movement in the VR world hit your retina cannot take more than 20 ms.

Image quality is also an issue, but not in terms of fidelity or quality. Instead, a display with low persistence that combats the blurring of the flat screen and a refresh rate of at least 90 Hz are important factors in enabling presence. The physical resolution of the screens must also be so high that the user’s eye cannot see the pixel structure of the display. Finally, the horizontal field of view must be at least 90 degrees.

This is not an exhaustive list of attendance requirements, but it is the key ones. Achieving all of this is something as compact as a modern VR headset like the Oculus Quest 2 is a marvel of engineering!

Presence is a constant challenge

While VR engineers and researchers cracked the code regarding minimum presence requirements, that doesn’t mean there isn’t much left to do. There is a lot of leeway to enrich the sensory experience of VR. Better haptics and additional sensory input for smell and taste are a few examples. Making headsets less intrusive and providing a full field of view is also high on the list of VR development goals. VR finally brought a sense of presence to the table, but it’s just getting started.

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