Is this real life?
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.
