WEBVTT
Kind: captions
Language: en

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What you're seeing is impossible.

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Lasers travel at the speed of light,

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and the only way that a blaster bolt,
or a disruptor shot, or a phaser beam

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can take this long to cross a room

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is in science fiction,
so the audience can understand what's going on.

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But... this is real.

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Over there–
and I can't look at it

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unless I'm wearing these incredibly-stylish
laser safety goggles–

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but over there is a
class 4 laser generator,

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the sort of thing that will burn your retinas out
if you treat it the wrong way.

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But lasers can't do this.

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They certainly can't start moving
back and forth, like it's a tennis match,

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and they absolutely can't behave
like they do in Star Wars,

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when Kylo Ren uses the Force

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and stops one in mid-air.

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But this is not being added
by computer afterwards.

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This is happening in-camera.

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I can interact with this
and show you.

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So how's it being done?

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To explain that,

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we need to talk to the person
who programmed that laser.

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- I'm Seb Lee-Delisle,
and I'm a digital artist and laserist.

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Definitely a real job!

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I make a lot of primarily
large, outdoor installations.

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I project onto buildings and
have lots of interactions with the public

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with musical instruments that I made.

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This laser is a really good
three-watt laser.

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It's fairly compact,
but it's got really fast scanners in.

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The big laser is an 11-watt laser
made by a company called Lightspace.

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The scanners aren't quite as good
as the ones in here,

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but they're still perfectly acceptable
and what most people use.

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- Alright, so...

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Can this burn me?
- Yeah.

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- Okay.

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- You're ruining my test now.
- Oh, sorry.

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- It's actually a very simple concept,

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and it didn't take me that long
to get it working.

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All of my code is C++.

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In this case, I had to tweak it
at a really low level

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because there were some really fine
timing adjustments that I needed to make.

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Here's the trick,

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and it's something you've probably seen
on Science YouTube before:

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rolling shutter.

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See, modern cameras don't take
a single frame all at the same time–

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boomph– like an old-school photograph,
they scan.

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It takes just a fraction of a second
for it to go from the top,

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all the way to the
bottom of the camera,

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and it registers each line
one at a time.

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So what we've done is we've
turned the camera 90 degrees on its side,

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so now that rolling shutter effect
is going horizontally,

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and this laser is being turned on and off
incredibly quickly and incredibly precisely,

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so that as the camera scans by
for every frame,

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the laser is on when it needs to be
and off when it needs to be.

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That takes a lot of maths
and a lot of precision,

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but the result... is this.

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- The harder thing about
programming this particular trick

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is to start thinking
in a different coordinate space...

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Right? Because you're no longer
dealing with X and Y particularly.

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Instead, you've got one of your axes,
which is the Y axis,

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which is now time.

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One of the things I had to take into account
is obviously when you start the app,

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when you start the camera,
those things aren't gonna be in line,

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so I had to add the capability
to be able to

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actually shift that start point at the frame
backwards and forwards in time.

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I'm certainly not the first person to
exploit the rolling shutter effect

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to make laser beam effects.

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In fact, you can pretty much just run
any traditional laser queue

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and just start to see
some weird things happening

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if you mess around with your
shutter speed and frame rate.

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You might have seen some really good
uses of it, in the past,

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with Adam LaBay
and his work with YouTube,

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and then subsequently with Saturday Night Live.

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What I'm doing here
is a little bit different from that,

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because we're literally taking
the area of the frame in time,

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and using that as a specific Y-position
that we want something to appear in.

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When we're all together,
and we're just seeing it for the first time,

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that was pretty special
to get that surprise,

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'cause I've only been testing this effect out
with some much smaller lasers in my studio,

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so when we got it actually
with the bigger laser in such a big space,

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yeah, it came to life.

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And I'm a bit surprised
how it looked.

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- Oh, what?!

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Oh, that looks good!
That looks so good!

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- I'll be preparing a video especially with
more of the behind-the-scenes stuff.

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More of the nerdy details.

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I'll be putting that in a separate video
on my channel.

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- I want to be clear,
Seb did all the hard work here.

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I am just the guy who went:
"What if we turn the camera on its side?"

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But while we've got all this setup,
and all this equipment, and these glasses,

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there is one effect I wanna try:

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the bullet dodge from The Matrix.

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Catch is... we can't
do this in slow motion,

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so I've... just gotta fake it.

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How hard can it be?

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That is hot.
That is very hot!