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# Introduction to rendering

## Video transcript

Hello. Hold on for just a second, please.
[Computerish sounds] Welcome to "Rendering." I'm Christophe Hery and
I'm a researcher at Pixar. Rendering is the last phase of
the pipeline of film production that takes our movies
from this to this. Rendering is where the world we've created
in the virtual three-dimensional space of the computer is finally realized
as a series of perfectly rendered two-dimensional images
that play one after another for 96 minutes and
become our movie. Rendering is an incredibly
time-consuming process, all focused on answering
one simple question: "What color is this pixel –
and then this pixel – and then this pixel
and this pixel?" Seems simple enough. I mean, the balloon is blue,
so the pixel will be blue, right? Well not exactly. A pixel is a tiny portion
of the final image. It acts like a little window
into the virtual 3D world. To understand what
color it should be, we have to figure out
what part of the picture we see through that window. We translate this question
"What color is this pixel?" into math. This equation is called
the "rendering equation." It's a mathematical description of how
light bounces around in the environment. I know we said "color."
And this equation is about light. But there's a good
reason for that. Color is light – just light
of different wavelengths. [Modernistic sound effects] So when we ask the question,
"What color is this pixel?" we're really asking "What light is coming
through this pixel towards the camera?" The solution to the equation
will be the answer to our question. "This pixel is – purple?"
[Asks in an unsure way.] To render a movie like "Up,"
we have to ask this question: "What color is this pixel?"
billions and billions of times. But just like every part of this process,
each little calculation isn't hard to do. It's the layer upon layer
of calculation that makes it complex, but also makes it possible to bring
something this beautiful to the screen.