How animators light scenes in 3D-animated movies

• Lighting in 3D-animated films brings out the physical and emotional aspects of scenes and shots.
• Lighting artists have great control over the intensity and placement of lights while their computers help create subtle details like shadows and reflections.
• In Netflix's "Over the Moon," lighting helped make Fei Fei's jacket look shiny and Lunaria look completely different from earth.

Following is a full transcript of the video.

Narrator: This is a shot from Netflix's "Over the Moon" while the film was still in production as Fei Fei and her pet bunny, Bungee, fly to the moon.

And here's the final version you see in the film. You'll notice that Fei Fei's skin now looks more like human skin and the lights from her control pad properly reflect off her helmet, making the shield appear more like glass.

The one ingredient responsible for this transformation? Lighting.

But lighting 3D-animated movies isn't only about the decisions that make scenes look more realistic. It's also about the emotional choices that turn this image into something magical.

Fei Fei: I did it! I did it!

Narrator: So, how exactly does lighting in animation work? And, warning, spoilers ahead for "Over the Moon."

Lighting is one of the final elements added in 3D animation, but animators have to think about it early on. A lighting artist's decisions are guided by blueprints called color scripts, which come before anything is animated. These are hand-painted pictures that break down an animated film scene by scene.

By viewing them all next to each other, the director and production designer can break down the emotional story arc. And lighting here is key.

Celine Desrumaux: I'm trying to see in the big story. Which is the lowest point? Like, the saddest moment? Which is a more action moment? Which is a more funny moment or the most extravagant moment?

Narrator: That's Celine Desrumaux, the production designer for "Over the Moon." Celine used color scripts to decide how they'd create a contrast between Earth and the moon kingdom of Lunaria.

She found that by making the colors on Earth less saturated, the colors of Lunaria, with all of its light-emitting structures and characters, would look even bolder. Later on, the color scripts get redefined into a color key, which tells the lighting team how light or dark a given scene or shot should be while also identifying the exact number of lights, light sources, colors, and even how much shadow your subject is casting.

All of this information is necessary for Clara Chan, a CG supervisor who led the lighting team at Sony Pictures Imageworks for "Over the Moon."

Clara Chan: Pretty much we control the intensity, the placement of the lights, the colors.

Narrator: While lighting in live-action movies illuminates what's already physically there on screen, lighting animated movies works a bit differently. Without it, the physical appearance of what we see on screen is completely altered and won't look as realistic.

This happens in a few different ways.

First is a process called surfacing, which determines an object's texture and how an object will appear once light hits it. Things like roughness and shine are decided through surfacing. To put it simply, surfacing artists will assign numerical values to something like Fei Fei's jacket, perhaps a high value for reflectiveness and a low value for, say, roughness, but we won't be able to see what those values do to the surface until lighting artists actually add the light.

To see just how surfacing works to make a scene more real, let's take a closer look at the characters' skin. Before the lighting is added in this shot, Fei Fei and Chin's skin looks opaque. Once bright yellow light is added, the shot not only becomes much more colorful, but their skin is also taking in some of that color and light.

Chan: Human skin is translucent, and when light gets in, it bounces around inside, so you get this glowiness. Narrator: The subtle glow throughout the skin makes it look like real skin instead of plastic. But making an animated surface look good also requires figuring out how light behaves in real life.

Animators place many lights by hand, but there can be so much light in a given shot that computers need to lend a helping hand. 3D animators do this using ray tracing, a rendering method that requires a lot of computing power in which the virtual camera shoots out a light-sensing ray until it hits an object in the scene. If the object is transparent, the light will travel through it. And if the object is reflective, the light will bounce off at an angle

. They can also use the more advanced path tracing, which sends out multiple rays at once. As you can see, instead of going right to the light source, the rays bounce around the room, hitting every possible angle until they locate the light source. As the light bounces around during path tracing, subtle shadows and reflections are produced.

Take a look at this shot from "Incredibles 2," which takes place in a school hallway, so the primary light sources are these overhead fluorescent lights. The rays bouncing around the scene determine the shadows cast by these background characters, the shadow of Violet's hair on her shoulders, and even the reflection seen on this clock behind Tony.

Path tracing is why newer animated films look so real compared to older animations, which didn't have the processing power we do today. It gets more complicated when characters and objects are lit by multiple light sources, like the scenes where Fei Fei and her extended family celebrate the Mid-Autumn Festival. Here, there's some light coming from the kitchen behind them, but mainly from the lanterns above their head. That means the computer has to chart the path of each ray of light coming from each light source that makes it to the camera's lens.

Chan: There is the moonlight also in there, but in a lesser intensity so we could feel the actual lanterns hanging above them.

Narrator: As Fei Fei goes inside, you can see her bangs cast shadows. The computer calculated that the shadow of her bangs could cover a lot of her eyes, so the lighting team made the decision to break the rules of reality and eliminate or lighten them when necessary to help the audience better see her facial expressions. But it's not just up to computers to make light look real.

Lighting artists need to study how light acts in reality by observing the real thing, like that in order to see the surface of water, you need a reflection. This is exactly what Pixar did when creating the underwater world of "Finding Nemo."

According to Pixar director of photography Danielle Feinberg, the team took a real clip of underwater footage, recreated it in the computer to break it down, and found its most prominent feature was light. It impacts everything, from visibility to color. They found that objects lose their full color as they travel further into the water.

Meanwhile, these light beams help guide the eye, showing the viewer which way is up in shots where the surface is invisible. But through rendering, these subtle light features, known as caustics, showed up on the ocean floor. It's one of the many ways light realistically reacts to water in the movie.

But lighting's purpose isn't just about physically improving the look of an animated project. It also helps set the mood and emotional arc established by the color scripts. While "Finding Nemo" created nearly photorealistic water, it also defied those same rules to make a scene more emotional. Danielle found that one of the lighting elements they had the most leeway with was color.

So while the water in Sydney Harbor is actually turquoise, the lighting artists instead made the water mucky and green to represent one of the film's emotional low points.

In that "Incredibles 2" hallway shot, they weren't just looking at how light realistically behaves. According to Pixar lighting artist Charu Clark, the fluorescent lights created a sterile and uncomfortable feeling, which mirrored how Violet felt at the moment her crush couldn't remember who she was.

Later in the movie when Tony finally remembers Violet, the same location is lit up with bright sunlight to evoke a happy ending and the two characters' fresh start.

Different lighting for a different mood.

Meanwhile, when Fei Fei and Chin first arrived on Lunaria, it wasn't just about making their skin and outfits stand out more. The filmmakers wanted to create a sense of awe and an overwhelming feeling of wonder for the audience. So they filled this shot with bright, glowing yellow light emitted from the structure around them.

Desrumaux: I wanted to, like, keep a space for the audience to be amazed for when they're going to the moon.

Narrator: And during those family dinners, especially the one after Fei Fei returns from Lunaria, they wanted to create a warm and festive mood. So even though there's light from the moon and the kitchen, the lighting artists chose to amplify the light from the lanterns to set the right emotion for the scene.