What Is Virtual Reality?

October 17, 2018

VR is above all the art and science of immerging a user in a virtual environment so that he can feel unconsciously present in it. Immersion and presence are thus the key points to understand what VR really means, though they can seem confusing. In this article, we will approach each notion to offer you our definition of virtual reality, providing you keys to understand what is important in a high-quality VR application.

What Do You Need to Get Immersed?

The most common systems used in VR are the Head-Mounted Display (HMD), the CAVE or Immersive Cube, and the Desktop systems.

A cave VR system

CAVEs or Immersive Cubes

This system was one of the most widely used in the industry before the advent of the HMDs in the last couple of years. Multiple users can fit in a Cave, enabling collaboration. The system is often made up of 4 screens with 4 stereoscopic projectors.

Head-Mounted Display (HMD)

HMDs made their debut in 1966 , but only became mature very recently with the creation of the Oculus Rift and the HTC Vive. HMDs consist of a screen that stands in front of your eyes and sensors so that the computer knows where your head is in space.

oculus vr gear
zSpace, an AR and VR system

Desktop Systems

Many desktop VR systems exist, but the industry mostly uses the zSpace and the Personal space station.

Feeling Present

As said before, presence is the key point to define virtual reality. Without this feeling of actually being somewhere else, your system is just an interactive 3D system, not a true VR one (even if it costs millions of dollars).

Once you create presence, the user will experience natural reactions and emotions. For instance, if you are on top of a high cliff, you will experience the fear of heights. If a virtual ball is thrown at you, you will try to catch it. If an avatar saves you from certain death, you might actually smile at him. True story!

This is also why VR is really useful for engineers: they can evaluate their design as they would in real life but without the constraints of reality.

Cognitive Presence

Presence is for sure a complex and subtle topic. Mel Slater is one of the scientists conducting some of the most interesting research on presence. In a well-known article, he splits presence into two: cognitive presence (the mind) and perceptive presence (the senses).

Most people report presence when playing a game, watching a movie, reading a book, or just hearing a story (the roots of VR). This is actually cognitive presence: where their mind takes them to another world.

An immersive VR system

Perceptive Presence

All of these experiences lack perceptive presence, which is in fact fooling your senses in a realistic way. Vision, but also sound, touch, smell… Keep in mind that humans are not able to perceive the world perfectly. Indeed, the human brain makes all sorts of simplifications, perfectly illustrated by optical illusions. Knowing the limits of human perception, which is a fundamental part of understanding VR, allows you to create perceptive illusions, such as redirected walking.

So, how do you achieve that? The most basic way of creating perceptive presence is by using head tracking. Moving your head and, as a result of this movement, seeing the world from a different viewpoint, is the basis for the action/perception loop. Thus you need to be able to move, and those moves must have an effect on the virtual environment. Your body is engaged: as Antonio Damasio says, “the mind is embodied, not just embrained.”

There are also several technical requirements such as a low latency, frame rate, wide field of view, interactions capabilities etc.


Breaks in Presence

If, as a result of your actions, you are not getting the result that you are expecting, your brain will know something is wrong. This is called a “break in presence” (BIP).

For example if the image freezes for one second while you are moving your head, your eyes will not perceive a movement and there will be a conflict between what you see (a frozen image) and what you feel (movement detected by your inner ear). This example affects perceptive presence which can quickly recover as soon as the feedback gets back to normal.

Another example is if your virtual arm penetrates objects like a ghost, or that a glass falls but does not break. The “rules” of the  simulation are not exactly the same as natural reality. This mostly affects cognitive presence as it reminds the user that he lives in a different reality.

If you have only one goal when creating a VR environment, it would be to create and maintain presence. Remember: feeling present in an empty room is VR. Not feeling present in a beautiful environment is not VR.

How Can We Measure Presence?

It is very difficult to concretely measure whether a user feels present in the virtual environment or not. This may be different for everyone. Indeed, there are currently no absolute indicators to measure presence. Even though you can measure the heart rate or skin conductance to evaluate anxiety, it is relevant only for stressful simulations.

However, you can try to evaluate if the user responds naturally to events occurring in the virtual environment he is immersed in. We already mentioned a few natural reactions you can observe. For instance, you can check if the user naturally tries to catch a ball, experiences fear of heights near a cliff, tries to protect his virtual body if somebody intents to hurt him, or if he avoids an incoming collision… These reflexes can show that the user is actually feeling present in the virtual environment.

We observe this very often during engineering meetings in Improov: people forget about technology and start immediately working, observing design issues, communicating around solutions and taking actions.


There is of course a lot more to be said about what is VR, but we hope this article got your attention on some fundamental points. We leave you with this quote:

“Our approach is to treat virtual reality as something quite new with its own unique conventions and possibilities that provide a media where people respond with their whole bodies, treating what they perceive as real.” – Mel Slater

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MiddleVR is a VR company focused on professionals founded in 2012.


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