Computers and computer technologies are important in a number of facets of motion picture production. Prior to computerization, animation and graphics relied solely on the technique of stop motion--where hand drawing or painting of many, slightly varied images is done and each image is photographed, frame by frame. When displayed at normal motion picture speed (24 frames per second), an animated image is produced. Now, software makes the computerized creation of animated images and scenes routine. Also, computerized enhancement or supplementation can change the character of films involving real people and objects.
Prior to computer animation and computer generated graphical images, animation could be produced two ways. Even in the present day, these methods are still used. The first animation method is to draw or paint a succession of cartoon frames, which are then combined into a film. The second method uses physical models capable of being repositioned. A model is positioned, photographed, repositioned, photographed, and so on.
Beginning in the 1970s, computer animation began to supplant the traditional animation methods. During that decade, computer technology developed so that computer animation became feasible to contemplate. Recognizing this, in 1973 the Special Interest Group on Computer Graphics met for the first time. Soon after, computer graphics were used in short films. While the quality of these efforts was poor, they attracted the attention of filmmaker George Lucas. Lucas explored the use of computer graphics in his second Star Wars movie, The Empire Strikes Back. The technology was not included in the final version of the film, but the experience laid the groundwork for Lucas's later embracing computer graphics as a crucial component of his films.
The 1980s saw the dedicated incorporation of computer graphics in movies such as Tron, Young Sherlock Holmes, Willow, and The Abyss. The latter enabled the creation of scenes that were literally impossible to achieve by conventional means.
Throughout the 1990s, the creative power of computer animation was repeatedly demonstrated. The technology had become a mainstream tool in movie making. The 1991 animated movie Beauty and the Beast, which incorporated computer graphics was nominated for an Academy Award for best picture. In 1995, the first completely computer animated movie, Toy Story, was made.
There are various ways in which computers can create an animated image. One technique involves creating objects and then rendering them. Rendering is the process of adding realism via the incorporation of three-dimensional qualities. For example, the technique of ray tracing incorporates variations in shade, color-intensity, and shadows that would be produced by the presence of one or more light sources. Ray tracing software simulates the path of a single ray of light and its subsequent absorption or reflection by the objects in its path. Also, the computer artist must specify various parameters, such as the intensity and color of the light source, and the light absorptive or reflective nature of the object surfaces that the light strikes. The software is complex, as a typical light beam consists of millions of rays. Enormous computational resources and advanced graphics systems are required. With this software, near-perfect, three-dimensional animation is possible.
Another computer animation technique involves standard computer painting tools. Single frames are painted and the frames are saved as files, or directly connected to a video. The files can be strung together later to create the moving image. A final method of computer animation involves the manipulation of images so that one image is gradually turned into another, termed morphing.
Computer generated images must accurately depict the movement of objects, animals, and humans. Motion control is thus, a major part of computer animation. Early animation programs depicted movement crudely. As animation technology developed, so-called scripting languages were written. One scripting system is ASAS (Actor Script Animation Language). ASAS allows for the definition of actors--objects with their own animation rules. This is similar to the behavior of objects in object-oriented languages. With the development of scripting languages, scenes became more realistic with a variety of independent motions occurring.
Other algorithms are necessary to specify other animation systems, which are required to convey realism in the animated images. Procedural animation defines movement as a function of time. The laws of physics can apply in this type of animation (for example, having a moving ball hit another object causing the second object to move). Another animation system is representation animation. This type of animation allows an object to change its shape. The objects can be complex and composed of connected rigid segments, such as a skeleton. Or, objects can be soft and subject to deformation, such as the movement of skin over facial muscles. Third, objects in representation animation can be morphed--changed from one shape into another, in two or three dimensions. A third animation system is called stochastic animation. This uses stochastic processes--processes that occur by random chance--to control groups of objects. Examples are animated images of fireworks, fire, or a waterfall. The final animation system is called behavioral animation. In this type, objects or "actors" are given rules about how they will react to an environment. An example is a flock of birds, where each bird behaves according to rules defined by the animator.
Computer generated imagery continues to progress. Now, human actors can be connected to a computer in order to record their movements, which will be used to create an image. Also, actor's faces can be scanned into a computer and used as a template for a life-like computer image. With this technology, the visual distinction between a human and a computer generated image is often difficult to discern.
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