Monday, November 10, 2008

Computer Generated Imagery

CGI or Computer Generated Imagery can sometimes be described interchangeably as Computer Animation. However, CGI typically refers too digitally created 3-D effects in live action films.

-CGI is often used as a cheaper and faster method of creating background imagery such as crowd scenes or scenes that require many extras and creating sets or environments that would otherwise
require major construction or elaborate small scale models. It is also used to create images that would not be possible any other way. It can also add simple effects such as smoke, fire, etc. and can delete unwanted visuals such as a wire, body part, etc.

-In 2-D animation, computers can: do in-between drawings, cel-coloring, and can reproduce backgrounds all more quickly and more cheaply than by hand. Animators can also get instant fedback on their work as opposed to older, slower methods such as a filmed pencil test.

Screening Room:

No Fate But What We Make: 'Terminator 2' and The Rise of Digital Effects (Van Ling, 2003)

This documentary is featured on the 2003 'Extreme' DVD release for Terminator 2: Judgment Day (1991).

Jurassic Park (Spielberg, 1993)

ILM & The Making of Hulk (2003)

This documentary is featured on the 2-Disc Special Edition DVD for Hulk (2003).

Hulk (Ang Lee, 2003)

The Matrix: Bullet Time

(Documentary on digital cinematography)

Spider-man 2
(Sam Raimi, 2005)

Important Terms:

Motion Capture (mocap) - also known as motion tracking, describes the process of recording movement and translating the movement onto a digital model. It is used in military, entertainment, sports, and medical applications. In filmaking it refers to recording actions of human actors, and using that information to animate digital character models in 3D animation it includes face, fingers and captures subtle expressions, it is often referred to as performance capture.

Rendering- is the process of generating an image from a model, by means of computer programs. The model is a description of three-dimensional objects in a strictly defined language or data structure. It would contain geometry, viewpoint, texture lighting and shading information. The image is a digital image or raster graphics image.

Note: 'Rendering' is also used to describe the process of calculating effects in a video editing file to produce final video output.

Morphing- digitally blending a CG imagery and real imagery.

This special effect in films and animations changes (or morphs) one image into another through a seamless transition. Most often it is used to depict one person turning into another through some magical or technological means or as part of a fantasy or surreal sequence. Traditionally such a depiction would be achieved through cross-fading techniques on film. Since the early 1990's, this has been replaced by computer software to create more realistic transitions.

Reflection Mapping- digitally simulating a mirrored surface, often by recreating what would be reflected in the mirror.

Reflection Mapping is an efficient method of simulating a complex mirroring surface by means of a precomputed texture image. The texture is used to store the image of the environment surrounding the rendered object. There are several ways of storing the surrounding environment. Two popular methods are the Spherical Environment Mapping in which a single texture contains the image of the surrounding as reflected on a mirror ball, or the Cubic Environment Mapping in which the environment is unfolded onto the six faces of a cube and stored therefore as six square textures.

Interpolation - creating digital frames in a film based on existing frames of live action scenes.

Also known as:

Tweening (short for in-betweening) - the process of generating intermediate frames between two images to give the appearance that the first image evolves smoothly into the second image.

The use of computers for inbetweening was pioneered by Nestor Burtnyk and Marceli Wein at the National Research Council of Canada. They received a Technical Achievement Academy Award in 1997, for their pioneering work in the development of software techniques for computer assisted key framing for character animation.

In the context of Adobe Flash, the process is simply called "tweening," and the resultant animation is called a "tween."

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