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Computer 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 produced by exploiting the persistence of vision to make a series of images look animated. Given that images last for about one twenty-fifth of a second on the retina fast image replacement creates the illusion of movement.
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 art of stop motion animation of 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.
For 3D animations, all frames must be rendered after 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.
One of the earliest steps in the history of computer animation was the 1973 movie Westworld, a science-fiction film about a society in which robots live and work among humans, though the first use of 3D Wireframe imagery was in its sequel, Futureworld (1976), which featured a computer-generated hand and face created by then University of Utah graduate students Edwin Catmull and Fred Parke.
Developments in CGI technologies are reported each year at SIGGRAPH, an annual conference on computer graphics and interactive techniques, attended each year by tens of thousands of computer professionals. Developers of computer games and 3D video cards strive to achieve the same visual quality on personal computers in real-time as is possible for CGI films and animation. With the rapid advancement of real-time rendering quality, artists began to use game enginesto render non-interactive movies. This art form is called machinima.
3.1 Early animation
Precursors to Animation
Fig: Five images sequence from a vase found in Iran.
Evidence of artistic interest in depicting figures in motion can be seen as early as the still drawings of Paleolithic cave paintings, where animals are depicted with multiple sets of legs in superimposed positions, clearly attempting to convey the perception of motion.
Other examples include a 5,200-year old earthen bowl found in Iran in Shahr-e Sukhteh and an ancient Egyptian mural. The Persian bowl has five images painted along the sides, showing phases of a goat leaping up to nip at a tree. The Egyptian mural, found in the thomb of Khnumhotep and Niankhkhnum, at the Beni Hassan cemetery. The paintings are approximately 4000 years old and show scenes of young soldiers being trained in wrestling and combat. Seven drawings by Leonardo da Vinci (ca. 1510) extending over two folios in the Windsor Collection, Anatomical Studies of the Muscles of the Neck, Shoulder, Chest, and Arm, show detailed drawings of the upper body (with a less-detailed facial image), illustrating the changes as the torso turns from profile to frontal position and the forearm extends.
Fig:Egyptian burial chamber mural.
Even though all these early examples may appear similar to a series of animation drawings, the lack of equipment to show the images in motion means that these image series are precursors to animation and cannot be called animation in the modern sense. They do, however, indicate the artists' intentions and interests in depicting motion.
Victorian parlor toys
Many of the early inventions designed to animate images were meant as novelties for private amusement of children or small parties. Animation devices which fall into this category include the zoetrope, magic lantern, praxinoscope, thaumatrope, phenakistoscope, and flip book
Zoetrope (180 AD; 1834)
The zoetrope is a device which creates the image of a moving picture. The earliest elementary zoetrope was created in China around 180 AD by the prolific inventor Ting Huan . Made from translucent paper or mica panels, Huan hung the device over a lamp. The rising air turned vanes at the top from which hung the pictures painted on the panels would appear to move if the device is spun at the right speed.
The modern zoetrope was produced in 1834 by William George Horner. The device is essentially a cylinder with vertical slits around the sides. Around the inside edge of the cylinder there are a series of pictures on the opposite side to the slits. As the cylinder is spun, the user then looks through the slits to view the illusion of motion. The zoetrope is still being used in animation courses to illustrate early concepts of animation.
The magic lantern
The magic lantern is the predecessor of the modern day projector. It consisted of a translucent oil painting and a simple lamp. When put together in a darkened room, the image would appear larger on a flat surface. Athanasius Kircher spoke about this originating from China in the 16th century. Some slides for the lanterns contained parts that could be mechanically actuated to present limited movement on the screen.
A thaumatrope was a simple toy used in the Victorian era. A thaumatrope is a small circular disk or card with two different pictures on each side that was attached to a piece of string or a pair of strings running through the centre. When the string is twirled quickly between the fingers, the two pictures appear to combine into a single image. The thaumatrope demonstrates the Phi phenomenon, the brain's ability to persistently perceive an image. Its invention is variously credited toCharles Babbage, Peter Roget, or John Ayrton Paris, but Paris is known to have used one to illustrate the Phi phenomenon in 1824 to the Royal College of Physicians.
Fig:A phenakistoscope disc byEadweard Muybridge (1893).
The phenakistoscope was an early animation device, the predecessor of the zoetrope. It was invented in 1831 simultaneously by the Belgian Joseph Plateau and the Austrian Simon von Stampfer.
Flip book (1868)
The first flip book was patented in 1868 by John Barnes Linnet. Flip books were yet another development that brought us closer to modern animation. Like the Zoetrope, the Flip Book creates the illusion of motion. A set of sequential pictures flipped at a high speed creates this effect. The Mutoscope (1894) is basically a flip book in a box with a crank handle to flip the pages.
The praxinoscope, invented by French scientist Charles-Émile Reynaud, was a more sophisticated version of the zoetrope. It used the same basic mechanism of a strip of images placed on the inside of a spinning cylinder, but instead of viewing it through slits, it was viewed in a series of small, stationary mirrors around the inside of the cylinder, so that the animation would stay in place, and provide a clearer image and better quality. Reynaud also developed a larger version of the praxinoscope that could be projected onto a screen, called the Théâtre Optique.
3.2 THE PRESENT
3.2.1 Traditional animation
The first animated film was created by Charles-Émile Reynaud, inventor of the praxinoscope, an animation system using loops of 12 pictures. On October 28, 1892 at Musée Grévin in Paris, France he exhibited animations consisting of loops of about 500 frames, using his Théâtre Optique system - similar in principle to a modern film projector.
The first animated work on standard picture film was Humorous Phases of Funny Faces (1906) by J. Stuart Blackton. It features what appears to be a cartoonist drawing faces on a chalkboard, and the faces apparently coming to life; whereas it was actually black line art drawn on white paper and then printed as a film-negative to look like white chalk.
Fantasmagorie, by the French director Émile Cohl (also called Émile Courtet), is also noteworthy. It was screened for the first time on August 17, 1908 at Théâtre du Gymnase in Paris. Émile Courtet later went to Fort Lee, New Jersey near New York City in 1912, where he worked for French studio Éclair and spread its technique in the US.
Influenced by Cohl, Russian scientist Ladislas Starevitch started to create animated films using dead insects with wire limbs. In 1911 he created "The Cameraman's Revenge", a complex tale of treason, suicide and violence between several different insects. It is a pioneer work of puppet animation, and the oldest known example of an animated film of such dramatic complexity, with characters filled with motivation, desire and feelings.
In 1914, American cartoonist Winsor McCay released Gertie the Dinosaur, an early example of character animation.
Traditional animation (also called cel animation or hand-drawn animation) was the process used for most animated films of the 20th century. The individual frames of a traditionally animated film are photographs of drawings, which are first drawn on paper. To create the illusion of movement, each drawing differs slightly from the one before it. The animators' drawings are traced or photocopied onto transparent acetate sheets called cels, which are filled in with paints in assigned colors or tones on the side opposite the line drawings. The completed character cels are photographed one-by-one onto motion picture film against a painted background by a rostrum camera.
The traditional cel animation process became obsolete by the beginning of the 21st century. Today, animators' drawings and the backgrounds are either scanned into or drawn directly into a computer system. Various software programs are used to color the drawings and simulate camera movement and effects. The final animated piece is output to one of several delivery media, including traditional 35 mm film and newer media such as digital video. The "look" of traditional cel animation is still preserved, and the character animators' work has remained essentially the same over the past 70 years. Some animation producers have used the term "tradigital" to describe cel animation which makes extensive use of computer technology.