Overview of the Computer Animation Process

Most computer animation projects have these stages, but in practice this process or production pipeline can adopt different forms and variations.

Preproduction involves all the conceptualization and planning that takes place before a computer animation project is produced. This stage in the process includes no visual tasks such as screenwriting and planning the management of the project, as well as visual tasks such as storyboarding and developing the overall visual look of the project. Preproduction is the foundation of a project. Inadequate or erroneous preproduction usually results in delays, cost overruns, and creative deficit. The production stage in the process of three-dimensional computer animation involves a series of standard steps: modeling, animation, and rendering.

First, the characters, objects, and environments used in three-dimensional computer animations are modeled. This computer modeling can occur with a wide range of computer-based three-dimensional techniques such as using virtual modeling tools to sculpt objects, or using a three-dimensional digitizer to capture the shape of a physical model directly into the computer program.
Once the virtual actors and objects are modeled, they can be arranged on the stage and can be animated with a wide variety of techniques. Computer animation techniques range from keyframing animation where start and end positions are specified for all objects in a sequence, to motion capture where all positions are fed to the objects directly from live actors whose motions are being digitized. The results of the animation can be previewed in the form of digital flipbooks displayed on the screen.
Once the objects are modeled and animated, they can be rendered. To minimize time and budget complications, motion tests are often produced to preview the computer animation sequences before the final production takes place. Computer rendering is the process of representing visually the animated models with the aid of a simulated camera. The lighting of the scene and the shading characteristics are often specified before the animation is laid out, but the rendering itself, the calculation of the finished computer-animated images, always happens after the modeling and animation parameters have been defined.

Once the images have been rendered, a variety of post processing and postproduction techniques can be applied to the images before they are recorded. For example, computer-generated images can be digitally composted or mixed with other computer-generated images or with live action. Computer animation can also be distorted, retouched, processed, or color corrected using postproduction techniques. When computer animations are completed, they are usually recorded on videotape or film so that they can be shown later on a TV screen or in a movie theater. Each film and video format has unique requirements and characteristics. For example, the standard rate of display of animated images recorded
on videotape is 30 frames per second; on film it is 24 frames per second. Increasingly computer animation is delivered in a digital format that may be played back in real time as part of a multimedia interactive game.

What follows is an overview of the major stages in digital production of three-dimensional computer animation. The production process is never entirely linear, and some of the stages are usually staggered.

Story Development and Scriptwriting

Behind any great visual project there is a strong idea and a great story. The stage of story development takes place before production begins, especially in small projects where the writer develops the story before any other preproduction has started or any budget has been committed to the project. In larger projects story development marks the beginning of development. During this process the writer (or story/design team in a larger project) not only has to focus on developing the characters and the plot but he or she also has to adapt it to the strengths and limitations of the visual medium in question. Usually a few creative cycles and/or revisions exist between a story or a game idea and the final script or the game design document. Later in the process, the script needs to be broken down, or translated into a sequence of shots and a soundtrack, before production can start.

Visual Development

Visual development is about setting a visual direction and style for the project. This stage includes the creation of the characters, the types of environments and props, the overall styling, atmosphere and "look," and even the color schemes for the project. The visual development team is charged with creating concept art (as opposed to production art) usually includes painters, sculptors, and illustrators, and it is most active during the preproduction stage. Creating color palettes and the color keys for every scene of the project is an important aspect of the visual development process that will set much of the visual mood of the project. The color keys must complement visually the goals of each part of the story Imagine the difference in mood between a shot that has harmonious soft colors, and the same shot with loud contrasted colors.

Character Design

After the story, the characters are perhaps the second most important aspect of an animated project. The look of characters is developed through drawings, sculptures, and even computer-generated renderings. Visually speaking, it is important to determine early on the type of look for the character in question: cartoon, stylized, or realistic.
Character sheets and character turnarounds are two important deliverables from this stage of preproduction. The former consist of sets of drawings that define the attitudes and poses of the characters in the form of body positions and facial expressions, and the later show the key features of a character from different points of view

In developing the look of characters for computer animation one must keep in mind which techniques will be used to animate it and deliver it to an audience. A character for a real-time action computer game, for example, would have to be designed very differently from a character in a feature-animated film. A secondary character in an all computer-animated film would be designed differently from the starring virtual actor in a visual effects movie. The assistant character designers often design props used in a scene ranging from a small utensil to a vehicle. It is of critical importance for the character designers to consult with the technical directors who are in charge of modeling, setting up the animation controls, and rendering the character.

Storyboards

The creation of storyboards is usually the first attempt to translate the story and the script into images. In that sense, creating the storyboards is an important tool for breaking down the script into manageable production units, and it is also an indispensable tool for doing a technical breakdown of each shot. During story development the storyboards are also used to evaluate whether the storytelling needs fine-tuning. The storyboards developed early in preproduction tend to focus more on fleshing out the storytelling, general composition, actions, and camera moves and less on the technical derails. As this process evolves the storyboards generally include more production-oriented detail.
Storyboards are also used to put together a story reel, also known as Leica reel. A story reel is essentially a filmed version of the storyboard that matches the still images to the dialogue track. Story reels often include simple camera moves (like pans and zooms) to enhance the narrative.

Animatics and Previsualization

An animatic is a preliminary version or a rough cut of a computer animation and is used to visualize how the final project may be structured. Animatics are based on preliminary visual material such as wireframe or low-resolution motion tests. None of the special effects in an animatic are meant to be final, and often they are implemented with techniques that are cruder and less expensive than the techniques that are planned for the finished project. Simple hand-drawn sketches and still photographs are common replacements for complex dynamic effects when these are presented in the form of an animatic.
Most animatics are not concerned with having a great level of motion detail, but some turn out to be quite polished. These animatics with additional detail are used for previsualizing one or several sequences in a movie, such as ones that may be particularly complex to produce on a technical level. The motion of an animated character in a regular animatic, for example, may be jerky and only insinuated, while the same motion in a previsualization, or previz test must be as close as possible to the final motion. Animatics are like motion sketches, while previz tests present the actual action that has already been laid out and is in the process of being refined. Animatics are commonly shown to a client or an executive producer before the final production starts. In today's production environment, animatics are usually assem bled from digital fliphooks and simple live-action sequences that are composited digitally It is partly for that reason that animatics are increasingly produced in-house at the same place where computer animation is created; both exist in a digital format.

Scene Layout

While models for the characters, props, and environments are being built (sometimes even before) the positions and motions of the camera are blocked out using placeholder geometry. This stage is called scene layout and it is increasingly being done directly in the computer with simplified digital models. However, some productions still make extensive use of the traditional approach to scene layout, which is based on drawings that detail the composition of the shot within a specific animation field. The motion of the characters and the camera is usually indicated in these drawings with directional arrows.

Modeling

The task of modeling the geometry in a computer animation project is usually divided by type of model or by scene. In the former approach, popular with large projects, the models of the primary and secondary characters are assigned to a set of individuals or team while the props and the environments, called set dressing, is assigned to others. In the latter approach, which is perhaps better suited for simpler projects, the building of models for a particular shot is the responsibility of the individual or team in charge of that shot.

Set Up of Animation Controls

The internal skeletons that are most often used to animate characters are usually called animation controls. These controls are also called 1K chains (short for inverse kinematics) because chains of controls that use the inverse kinematics animation technique constitute the skeletons. In projects with a large volume of animations the setting up these animation controls is usually the responsibility of a technical director while the animators devote themselves to animating after the basic controls are set up.

Live Data Capture

The live data capture stage is especially important in visual effects projects that rely heavily on getting material from the live action set, whether it is a remote location or a sound stage. Most live data capture requires specialized equipment and software specialized in motion capture; three-dimensional scanning of actors, props or terrain; and even plain live action cinematography. A dedicated unit (often external to the animation team) is usually in charge of preparing all of these elements for the animators to use them as guidelines in their animation.

Texture Painting

Most three-dimensional computer animation projects make extensive use of textures for the geometry. Many of these textures are painted by hand directly with a digital paint system or with traditional materials and then scanned. Photographic textures that are captured on film need to be scanned, and those captured with digital cameras can be transferred digitally to the system. In any case all photographic textures usually require some sort of touch-up or color balance work before they can be applied to the geometry Texture painting and touch-up is usually done by painters, often from the visual development team. In some instances the texture painters have to work with the technical directors who are in charge of developing procedural textures

Character Animation

Character animation is done in stages, starting with rough animation and ending with animation clean up. The broad motions are usually blocked in first and proxies, or placeholder geometry, are generally used to do this. The secondary actions and the facial animation are added next, and finally the details are cleaned up and the timing of overlapping motion is fine-tuned. Like modeling, the animation tasks are also usually divided among different individuals or teams. A common way to parcel out the animation deliverables is by character or by scene. The animation of crowd scenes is usually assigned to a separate group, which is often part of the effects animation team. Flipbooks contain many still frames and are useful to preview and fine tune the animated sequences.

Effects Animation

The effects animation team is in charge of animating the natural phenomena like rain, wind, and fire. Most of the techniques used to animate natural phenomena today are procedural so often the effects animation team is largely composed of technically oriented animators. In some productions the animation of crowds is taken care by the effects animation

Lighting, Shading, and Rendering
Different teams sometimes do lighting and shading. Lighting involves the placement and fine-tuning of all the light sources in every shot of the film. Shading involves developing the shaders that are used throughout the production. As with the creation of procedural textures, some aspects of lighting and shading are often done by programmers or by technically inclined artists who are able to write shaders. This process is often a direct result of the look development stage when most components that impact the final look of the rendered images are defined. Jobs are sent for final rendering when all the rendering variables are set. Small files are often rendered in one pass, and all the elements are rendered at the same time. Larger files with complex geometry or complex renderers are often rendered in layers, each with a different element of the shot that require further compositing.

Compositing, Postprocessing and Final Output

After the elements of a shot or a scene have been rendered, they are assembled and composited before the final recording takes place. Stills or sequences that might need retouching or mistakes fixed are also taken care of during this. The logical culmination of the computer animation production process is the recording of the image onto a wide variety of media including film, videotape, DVDs, and paper.

Media Asset Management and Technical Support

An often invisible but crucial component of the digital production flow is the management of the different art or media assets that make up a computer animation production. While there are several off-the-shelf media asset management software programs, some of the main challenges remain the constant revision of assets and the large number of people often involved in generating a single frame of animated action or visual effects. Media asset management requires daily discipline; an easy-to-understand system for identifying files from different scenes, shots, and revisions; and frequent digital backups of the data.

The technical support group is a key component in all computer animation productions. These individuals are not directly involved in the creation of the art assets-or, as they say in Hollywood, they do not "touch the product." But without their diligence, vigilance, and quick response to technical problems, most computer animation projects would be truly unmanageable.