What Is Rigging in 3D Animation? Basics and How It Works

3D computer animation can seem a lot like magic. How does a graphic artist’s sketch of a character get transformed into a lifelike, 3D animation that’s able to walk, crouch, jump, and use its limbs and hands as naturally as you or I can?

With 2D animation, motion is created frame by frame. Computers have since revolutionized animation, replacing hand-drawn frames with computer simulations that control how everything on-screen moves: cloth, leaves on trees, and even the 5.4 million hairs on an animated monster.

But before a computer can take an artist’s rendering of a character and bring it to life with motion, it has to go through an important phase: 3D rigging.

It’s part art and part science, and here’s a look at how it works.

The basics of 3D animation: Skins, skeletons, and simulations

Imagine a character in your favorite animated film or game. The way it looks and moves is a sum of three important things:

1. The “skin,” which is how it looks on the surface, also called a 3D mesh.
2. The skeleton, which is used to control the way it moves with interconnected bones, muscles, and joints, also called a rig. Before a character can be animated, it needs to be rigged.
3. The movements, which are simulated by a computer based on the properties of the internal skeleton. These also affect vertices, or points, on the 3D mesh to alter skin, clothing, facial features, etc. along with the movements.
   

Together, these make it possible for an animator to control how a character looks and moves. External elements like shadows and light build more realism, but the above are self-contained and help animators create more-realistic, organic characters.

Good bone structure: How “bones” make skeletal animation possible

Before a 3D model can be animated, it has to get a rig. Let’s talk about this by thinking of a 3D character as a hand-sculpted clay model.

Once a model has been created by an artist, it’s inanimate, stuck in its original position until you manually bend an arm or turn its head. You can imagine that creating motion by hand for a feature-length film would be extremely tedious. To automate the process, computer animation programs allow animators to assign motions. For that to happen, animators have to transform characters from clay models into marionettes. That’s where 3D rigging comes in.

3D rigging creates a skeleton for a 3D model—all the bones and joints inside a character that give animation software vertices it can recognize. Each bone is assigned properties and constraints, just like bones in a human skeleton. They can rotate, bend in certain directions, and control the motion of other bones. Bones can be weighted so that they have more influence over other bones, and a “master bone” can be set that controls the center point of how a character moves.

Starting to sound complex? It gets even more technical when you start animating facial expressions. Using programs such as Unity and Blender, animators can use drivers, morphs, kinematics, and weight painting, among other tools, to control nearly anything on a character—say, raising the left eyebrow for a curious look or raising both for a surprised look.

The key takeaway: Rigging is a highly complex, very necessary step in the animation process. Rigging allows a character’s body to be articulated in a structured way. Without it, trying to animate a character would result in a very distorted, deformed mesh.