Or is it all in your head?

This is virtual reality.

Or it can be, if you’re wearing a headset that lets you enjoy VR.

If you haven’t done this already, now’s the time to put on your VR headset.

This could be as simple as google cardboard, or as fancy as these little beauties.

This is a VR180 video, which means you’re going to see all around in a hemisphere.

Some things will look close to you, others will look far away.

It’s okay if you just use your phone or desktop computer - you can scroll around to

see the extra visuals.

So what does this mean, to experience virtual reality?

With traditional media, you’re a spectator.

When you watch a movie, you peer into a window where events are taking place.

Even when you ARE participating in the action, say - playing a video game - you’re never

fooled into thinking you’re REALLY there.

But Virtual Reality makes you actually FEEL like you’re in a different place.

You’re here with me, rather than where you actually are.

We call this VR experience PRESENCE.

VR tricks your brain into feeling like you’re IN a 3D world,

and not just watching a 2D video.

It does this by showing a slightly different picture to each eye.

By contrast, in traditional media, we show the exact SAME picture to both eyes.

This would be how a cyclops sees the world.

But with VR, we’re essentially replicating how we humans see naturally - with TWO eyes.

Our eyes are separated a small distance - on average, about 63 mm.

That means each eye sees an object from a slightly different angle.

You’ve probably done this before - hold up your finger.

Look at it with just your LEFT eye,

now just your RIGHT eye,

- LEFT eye -

RIGHT eye

It looks like your finger is jumping back and forth.

Objects that are farther away jump less.

We call this PARALLAX.

This phenomenon helps us understand depth.

We need two eyes seeing slightly different images for depth perception.

Your brain also pays careful attention to cues like the relative sizes of things to

tell you which is farther away.

The farther away, the smaller something appears.

We also look for SHADING to get a feel for the depth of an object.

Now let’s go deeper.

To understand the science of VR, you first have to understand the science of vision.

Let’s talk about how our eyes and brain work together.

Light comes into your eye through the pupil and is focused by the lens onto the retina

in the back of our eye.

That’s where we have light-detecting cells - rods and cones.

These cells convert light energy into electrical signals.

A little bit of processing of the signal happens right in your eye, and then the summed-up

signal is sent through your optic nerve coming out of the back of each eye into your brain.

Some information crosses over at the optic chiasm.

You bundle together info from the outside half of the retina on the same side of the

head and from the inside half of the retina on the other side of the head.

Next the information is relayed through the optic tracts to a station in the thalamus

called the lateral geniculate nucleus.

Finally, it reaches the back of your brain, a region called the Occipital Lobe.

Now here’s where the two separate streams of information are joined together to form

one image.

So we start with two different pictures from our two eyes, and our brain integrates them

into one image.

How can we begin to replicate these events?

For starters, what if we could capture what each eye sees?

That’s how VR is filmed.

We shot this video using a special kind of camera - really, it’s like two cameras,

put together.

It has two separate lenses, just like how each of your eyes has its own lens.

We’ll explain in more detail about how the cameras work in our video about the Technology

of VR.

Today, let’s focus on the Science of VR.

The experience can be filmed in real life, or it can be completely virtual.

The key is that the two images should be separated by around the same distance and angle from

each other as if your two EYES were capturing the images.

If the lenses are too close together, or too far away from each other, the whole thing

falls apart.

Next, the two images are stitched together, using software that creates what looks like

a distorted image on a single 2D display.

But if this single image is viewed through two separate eyepieces, it re-creates the

experience of being there, seeing those two slightly different images through your two

eyes.

Your brain takes care of the rest.

As far as your brain knows, you ARE seeing these two separate images and not this manipulated,

stitched together creation.

This may feel like magic, but it’s not.

It’s science.

Today we’ve learned how we use the information from both of our eyes to experience our world

in 3 dimensions - but remember, sight is not our only sense.

There are other cues your brain uses to understand your environment.

For instance, hearing sounds coming from different locations.

We talked about how your eyes see slightly different information.

The same is true for our two ears.

Spatial sound can help sell the VR experience.

We also constantly monitor where our body is in space - we call this proprioception.

Maybe we need to wear a suit that sends our whole body cues...

Stay tuned for more and more immersive experiences in this virtual world.

We’d like to thank our friends at VR Scout and the YouTube VR Creator Lab for helping

us get started in the world of VR.

If you’ve enjoyed hearing about VR and want to learn more, check out our videos about

The Technology of VR and The Math of VR.

And let us know what other VR experiences you’d like to see in the comments.

We’ll be right here.

Waiting to hear from you.