Computer animation

Computer animation is the way we make pictures move on a computer. It is a kind of computer-generated imagery that only makes moving pictures, not still ones. Modern computer animation usually uses 3D computer graphics to look real.

Computer animation grew from older ways like stop motion and traditional animation. Artists now use computers instead of real objects or drawings. This means one person can make animations without actors, sets, or many props.

To make things look like they are moving nicely, a new picture shows on the computer monitor many times each second. This often happens at 24, 25, or 30 pictures per second. This is how television and motion pictures make things look like they are moving. If the pictures change too slow, the movement will look jumpy and not smooth.

Computer-generated animation

Computer-generated animation includes both 3D and 2D animation. Creators use code or software instead of drawing by hand. There are many ways to make these animations. Some ways are inspired by traditional animation, like key frame animation. Others are only possible with a computer, such as fluid simulation.

Animators can use math to change how things like mass, force, and gravity work. This helps them create exciting and imaginative scenes. Tools like onion skinning let 2D animators see their work smoothly, and interpolation helps 3D animators fill in movements automatically.

3D computer animation

Overview

In 3D computer animation, objects are made on a computer screen and given a special structure like a virtual skeleton. An animator moves parts of the figure, such as its arms or mouth, by setting special points called key frames. The computer fills in the movements between these points automatically, a process called interpolation. Finally, the animation is turned into a finished video through a process called rendering and compositing.

Before it’s finished, 3D animations are just shapes and systems inside the computer. They need to be rendered to become a movie or video game. Rendering can happen later for films or in real time for games. After rendering, the animation can be combined into the final product.

Animation attributes

For 3D objects, special features can be changed over time, like moving, growing, or rotating. These changes are controlled using keyframes, which can be layered or used to control other parts of the animation. For example, moving a character’s arm joints can change the whole shape of the arm.

Interpolation

Animation software connects keyframes using special curves, which helps create smooth movements. These curves can be adjusted to control how the movement looks. Interpolation lets animators change movements easily without redoing all the in-between steps. It also helps create complex motions, like circular paths, with just a few keyframes. Animators can adjust the speed, timing, and size of movements at any point.

Procedural and node-based animation

Some animations are made using tools that follow rules automatically. For example, noise can create natural movements like swarms of bees. Node-based animation lets animators build sets of rules to control many objects or very complex shapes at once, such as making particles move with the rhythm of music.

Disciplines of 3D animation

There are many special areas in 3D animation, like creating realistic hair for characters, each with its own tools and methods. When combined, these areas form what is called the 3D animation pipeline.

2D computer animation

2D computer graphics are used for style, low internet use, and quick real-time renderings.

Computer animation is like a digital version of old stop motion tricks, but it uses 3D models and traditional animation methods with 2D drawings shown one after another.

For 2D figure animations, separate drawings and clear layers are used, sometimes with a virtual frame to help them move.

2D sprites and pseudocode

In 2D computer animation, moving objects are often called "sprites." A sprite is a picture with a set place. By changing where the sprite is shown a little bit each time, it looks like it is moving. The following pseudocode shows how to make a sprite move from left to right:

var int x := 0, y := screenHeight / 2; while x < screenWidth do { drawSprite(x, y); x := x + 1; }

Timeline of computer animation

See also: Video game graphics

Early digital computer animation started at Bell Telephone Laboratories in the 1960s.

In 1967, a computer animation named "Hummingbird" was made. In 1968, a computer animation called "Kitty" was created, showing a cat moving. In 1971, an animation called "Metadata" was made, showing different shapes.

An early step in computer animation was the sequel to the 1973 film Westworld. The sequel, Futureworld (1976), used 3D wire-frame images. This first appeared in a student film A Computer Animated Hand, finished in 1972.

Developments in CGI technology are shared each year at SIGGRAPH. Game creators and 3D video card makers work to make quality pictures on computers in real time. Artists started using game engines to make non-interactive movies, leading to the art form Machinima.

Film and television

CGI short films have been made as independent animation since 1976. Early examples of movies using CGI animation include the films Star Trek II: The Wrath of Khan and Tron (both 1982), and the Japanese anime film Golgo 13: The Professional (1983).

The first full-length computer-animated TV series was ReBoot, which started in 1994. The first full-length computer-animated movie is Toy Story (1995), made by Disney and Pixar.

Computer animation became very popular for special effects. Movies like Avatar and The Jungle Book use CGI for most of the movie. Today, computer animation can look so real that films like The Lion King (2019) are advertised as if they were made with real actors.

Animation methods

In 3D computer animation, animators create a simple shape of a character, like a skeleton or stick figure. This basic shape is called a bind pose or T-Pose. Each part of this shape has special settings called animation variables, or Avars, that tell where it should go. For people or animals, these often match real bones, but they can also be used for things like facial features. There are other ways to move faces too, like facial animation. For example, the character Woody in Toy Story uses Avars to move.

There are a few ways to decide these Avar values. Traditionally, animators set the Avars at important moments and let the computer fill in the movements between those moments in a process called keyframing. Another method is called motion capture, where a real person acts out the scene, and special video cameras record their movements. This performance is then used to move the animated character. Both methods are used in movies and games. Keyframing can create movements that are hard to act, while motion capture can capture the small details of an actor's performance, like in Pirates of the Caribbean: Dead Man's Chest.

Modeling

3D computer animation makes moving images by using 3D models of objects and planning their movements. These models are built with points, shapes, and lines in a space that has length, width, and height. Objects start as simple shapes and get more detailed with special tools. To look real, models are painted with colors and patterns called "textures."

Artists can make these models move in different ways. They can use special equipment to record real movements, or they can plan each movement by hand, or use both ways together. This helps create realistic actions, like a character walking or showing feelings.

Equipment

Computer animation can be made using a computer and special animation software. Simple programs can create great animations, but they might take a long time on a regular home computer. For movies and video games, very detailed animations need powerful computers called workstations. These workstations have many processors and are much stronger than home computers. Sometimes, many of these workstations work together, called a "render farm," to finish a movie in one to five years. Animators also use special cameras, tools for capturing movement, and editing software to make their movies. Programs like Blender let people create animations without needing expensive equipment.

Facial animation

Main article: Computer facial animation

Creating realistic human faces in computer pictures is very hard but very important. Scientists have worked for a long time to make faces move naturally. In 1989 and 1990, important meetings helped share ideas and encouraged more research.

Special systems help control how faces look and move. One system from 1976 uses 46 different actions, like biting lips or squinting. By 2001, another system included 68 ways to move parts of the face, and scientists have kept improving how faces look in computer pictures. They sometimes make faces show emotions using special models.

Realism

Realism in computer animation means making each part of the moving picture look very real, almost like a photograph. Some computer animations try to make human characters look and move very realistically.

Not all computer animations aim for realism. Many films feature characters that are animals, legendary creatures, superheroes, or have cartoon-like shapes. Computer animation can also copy other types of animation, like stop-motion animation.

Web animations

Many websites let people share their own short movies. This has created a big group of independent and amateur animators. With free tools on computers and several free animation programs, many users can make their own short animations. This ease of sharing has also attracted professional animators. Companies like PowToon and Vyond help by providing professional animations that anyone can use.

The oldest web animations were in the GIF format, which works easily on the web. However, GIF animations can be slow to download, especially on larger screens. For many years, Flash animations were popular, but support for Flash has since ended, especially on mobile devices. As internet speeds improved, raster graphic animations became more practical. Many animations were changed to digital video formats, which work well on mobile devices and save space through video compression. Today, HTML5 compatible animations using technologies like JavaScript and CSS make creating web animations easier. YouTube now offers HTML5 options for digital video, and APNG provides an alternative to GIFs with better transparency options.

See also: Comparison of HTML5 and Flash

Detailed example

Computer animation uses many ways to make moving pictures. It often uses special math to move and change 3D shapes, called polygons. These shapes can have colors, lights, and other effects added to them before the picture is shown. There are also tools that help people plan the movement of the animation. Another way to create animation is by changing simple shapes using rules, which makes the animation look good no matter how big or small it is.