Introduction to rendering

Hello. Hold on for just a second, please. Welcome to "Rendering." I'm Christophe Hery and I'm a researcher at Pixar. Rendering is the last phase of the pipline and 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. 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.