Computer animation, or CGI animation, is the process used for generating animated images by using computer graphics. The more general term computer-generated imagery encompasses both static scenes and dynamic images while computer animation only refers to moving images.
Modern computer animation usually uses 3D computer graphics, although 2D computer graphics are still used for stylistic, low bandwidth, and faster real-time renderings. Sometimes, the target of the animation is the computer itself, but sometimes the target is another medium, such as film.
Computer animation is essentially a digital successor to the stop motion techniques used in traditional animation with 3D models and frame-by-frame animation of 2D illustrations. Computer-generated animations are more controllable than other more physically based processes, such as constructing miniatures for effects shots or hiring extras for crowd scenes, and because it allows the creation of images that would not be feasible using any other technology. It can also allow a single graphic artist to produce such content without the use of actors, expensive set pieces, or props.
To create the illusion of movement, an image is displayed on the computer monitor and repeatedly replaced by a new image that is similar to it, but advanced slightly in time (usually at a rate of 24 or 30 frames/second). This technique is identical to how the illusion of movement is achieved with television and motion pictures.
For 3D animations, objects (models) are built on the computer monitor (modeled) and 3D figures are rigged with a virtual skeleton. For 2D figure animations, separate objects (illustrations) and separate transparent layers are used with or without a virtual skeleton. Then the limbs, eyes, mouth, clothes, etc. of the figure are moved by the animator on key frames. The differences in appearance between key frames are automatically calculated by the computer in a process known as tweening or morphing. Finally, the animation is rendered.
For 3D animations, all frames must be rendered after the modeling is complete. For 2D vector animations, the rendering process is the key frame illustration process, while tweened frames are rendered as needed. For pre-recorded presentations, the rendered frames are transferred to a different format or medium, such as film or digital video. The frames may also be rendered in real time as they are presented to the end-user audience. Low bandwidth animations transmitted via the internet (e.g. 2D Flash, X3D) often use software on the end-users computer to render in real time as an alternative to streaming or pre-loaded high bandwidth animations.
Computer animation development equipment
Computer animation can be created with a computer and an animation software. Some impressive animation can be achieved even with basic programs; however, the rendering can take a lot of time on an ordinary home computer. Because of this, video game animators tend to use low resolution and low polygon count renders so that the graphics can be rendered in real time on a home computer. Photorealistic animation would be impractical in this context.
Professional animators of movies, television, and video sequences on computer games make photorealistic animation with high detail. This level of quality for movie animation would take hundreds of years to create on a home computer. Instead, many powerful workstation computers are used. Graphics workstation computers use two-four processors, and they are a lot more powerful than an actual home computer and they are specialized for rendering. A large number of workstations (known as a render farm) are networked together to effectively act as a giant computer. The result is a computer-animated movie that can be completed in about one to five years (however, this process is not composed solely of rendering). A workstation typically costs $2,000-16,000 with the more expensive stations being able to render much faster due to the more technologically advanced hardware that they contain. Professionals also use digital movie cameras, motion or performance capture, bluescreens, film editing software, props, and other tools used for movie animation.
Computer-assisted vs computer-generated animation
Computer-assisted animation : Computer-assisted animation is usually classed as two-dimensional (2D) animation. Creators drawings either hand drawn (pencil to paper) or interactively drawn(drawn on the computer) using different assisting appliances and are positioned into specific software packages. Within the software package the creator will place drawings into different key frames which fundamentally create an outline of the most important movements. The computer will then fill in all the " in-between frames" commonly known as Tweening. Computer assisted animation is basically using new technologies to cut down the time scale that traditional animation could take, but still having the elements of traditional drawings of characters or objects
Computer-generated animation : Computer-generated animation is known as 3-dimensional (3D) animation. Creators will design an object or character with an X,Y and Z axis. Unlike the traditional way of animation no pencil to paper drawings create the way computer generated animation works. The object or character created will then be taken into a software, key framing and tweening are also carried out in computer generated animation but are also a lot of techniques used that do not relate to traditional animation. Animators can break physical laws by using mathematical algorithms to cheat, mass, force and gravity rulings. Fundamentally, time scale and quality could be said to be a preferred way to produce animation as they are two major things that are enhanced by using computer generated animation. Another great aspect of CGA is the fact you can create a flock of creatures to act independently when created as a group. An animal's fur can be programmed to wave in the wind and lie flat when it rains instead of programming each strand of hair separately.
An animation database is a database which stores fragments of animations or human movements and which can be accessed, analyzed and queried to develop and assemble new animations. Given that the manual generation of a large amount of animation can be time consuming and expensive, an animation database can assist users in building animations by using existing components, and sharing animation fragments.
Early examples of animation databases include the system MOVE which used an object oriented database. Modern animation databases can be populated via the extraction of skeletal animations from motion capture data. Other examples include crowd simulation in which a number of people are simulated as a crowd. Given that in some applications the people need to be walking at different speeds, say on a sidewalk, the animation database can be used to retrieve and merge different animated figures. The method is mainly known as "motion graphs".
Animation databases can also be used for "interactive storytelling" in which fragments of animations are retrieved from the animation database and are recycled to combine into new stories. For instance, the animation database called Animebase is used within the system Words Anime to help generate animations using recycled components. In this approach, the user may input words which form parts of a story and queries against the database help select suitable animation fragments. This type of system may indeed use two databases: an animation database, as well as a story knowledge database. The story knowledge database may use subjects, predicates and objects to refer to story fragments. The system then assists the user in matching between story fragments and animation fragments.
Another application of an animation database is in the synthesis of idle motion for human characters. Human beings move all the time and in unique ways, and the presentation of a consistent and realistic set of idle motions for each character between different animation segments has been a challenge, e.g. each person has a unique way of standing and this needs to be represented in a realistic way throughout an animation. One of the problems is that idle motion affects all joints and simply showing statistical movements at each joint results in less than realistic portrayals. One approach to solving this problem is to use an animation database with a large set of pre-recorded human movements, and obtain the suitable patterns of motion from the database through statistical analysis