# Week 2: Theory of Computer Animation ## Overview - Perception - History - Early Devices - 19th century - Motion photography ___________________ ## References - Jon Krasner's Motion Graphic Design & Fine Art Animation - Computer Animation Complete Chapter I. # Perception **The human visual system** has evolved to provide for survival in an ever-changing world; it is designed to notice and interpret movement: the eye–brain complex has the ability, under sufficient viewing conditions and within certain playback rates, to create a sensation of continuous imagery from such a sequence of still images. ## Underlying mechanism of animation **Persistence of vision / perception of motion:** the human visual perception retains an image for a fraction of a second after it disappears. If discrete images are alternated for shorter periods that this retention, the persistence of vision may fuse them into an apparently continuously moving image. However rotating a white-light source fast enough will create the impression of a stationary white ring. Therefore, it is necessary to explain it in terms of the perception of motion ([phi phenomenon](https://en.wikipedia.org/wiki/Phi_phenomenon), or [beta motion](https://en.wikipedia.org/wiki/Beta_movement)). [Animation basics: The optical illusion of motion (5:11) - TED-Ed](http://ed.ted.com/lessons/animation-basics-the-optical-illusion-of-motion-ted-ed) ## Failure to create the perception of motion ***1. Flicker*** - a sequence of images can be displayed at rates fast enough to fool the eye into interpreting it as continuous imagery. When the perception of continuous imagery fails to be created, the display is said to flicker. ***2. Motion Blur*** - the receptors in the eye continually sample light in the environment. If an object moves too quickly with respect to the viewer, then the receptors in the eye will not be able to respond fast enough for the brain to distinguish sharply defined, individual details. In a sequence of still images, motion blur is produced by a combination of the object’s speed and the time interval over which the scene is sampled. In a still camera, a fast-moving object will not blur if the shutter speed is fast enough relative to the object’s speed. In computer graphics, motion blur will never result if the scene is sampled at a precise instant in time; to compute motion blur, the scene needs to be sampled over an interval of time. ## Two rates ***1. Playback or refresh rate*** – the number of images that occur per second displayed in the viewing process. The playback rate is the rate related to flicker. ***2. Sampling or update rate*** – the number of different images that occur per second. The sampling rate determines how jerky the motion appears. The National Television Standards Committee (NTSC) format displays images at a rate of roughly 30 fps (More precisely, 29.97 fps). On the other hand, because an NTSC television signal is interlaced, smoother motion can be produced by sampling the scene every sixtieth of a second even though the complete frames are only played back at 30 fps. Film is typically shown in movie theatres at playback rates of 24 fps (in the United States) but, in order to reduce the flicker, each frame is actually displayed twice (double-shuttered) to obtain an effective refresh rate of 48 fps. Refresh rates of computer monitors are 60 fps or greater. ---------------------------- # History Early artists (even cave painters) attempted to depict movement in a static image by spatial repetition, such as animals with multiple legs or sequences in tapestries. Many of the references to animation are in the form of stories about conjuring a life force into some humanoid form: from *Pygmalion* to Shelley’s *Dr. Frankenstein*. Some of this history also includes trying to create mechanical devices that mimic certain human activity: from Jacque Vaucanson’s mechanical flute player, drummer, and defecating duck in the 1730s, to Wolfgang von Kempelen’s chess player in 1769, to Pierre Jaquet-Droz’s writing automaton of 1774, to the electromechanical humanoid robots popular today. *Hugo*, by Martin Scorseseis in 2011 is a movie with a homage both to Georges Méliès (A Trip to the Moon), and writing automata. - [The caveman cartoons: How prehistoric artists make their paintings MOVE](http://www.dailymail.co.uk/sciencetech/article-2207596/A-night-pictures-caveman-style-Prehistoric-artists-used-cartoon-like-techniques-make-paintings-move.html) By Damien Gayle - ['The Writer' Automaton](https://www.youtube.com/watch?v=bY_wfKVjuJM) ## Early Devices - Pre 20th century - [Thaumatrope](http://courses.ncssm.edu/gallery/collections/toys/html/exhibit06.htm) - [Flip book](http://en.wikipedia.org/wiki/Flip_book) - [Zoetrope, a wheel of life](http://en.wikipedia.org/wiki/Zoetrope) - [Phenakistoscope](http://en.wikipedia.org/wiki/Phenakistoscope) - [Praxinoscope](http://en.wikipedia.org/wiki/Praxinoscope) PoV(Persistence of vision) is exactly how [a flip-book](http://www.flipbook.info/index_en.php) works. Although the phenomenon was known in antiquity, the illusion of motion was not achieved until the 19th century in a variety of entertainment devices, of which the best known is the Zoetrope.  "Zoetrope". - [More optical devices from *Laura Hayes and John Howard Wileman Exhibit of Optical Toys*.](http://courses.ncssm.edu/gallery/collections/toys/opticaltoys.htm) ### Early projections 19th century 'illusionistic' theatre boxes included various movements and lighting effects achieved within a small model theatre. [Magic lanterns](http://en.wikipedia.org/wiki/Magic_lantern) dating as far back as the 1600s (Leone Battista Alberti) projected hand-painted slides using fire or gas light, using mechanical systems to add dynamic elements to the projected images.   Peep show image & peep box [Magic lantern peep show](http://commons.wikimedia.org/wiki/File:John_Thomson_Magic_Lantern_Peep_Show_1877.jpg) ## Motion photography During the 1860s, American photographer [Eadward Muybridge](http://en.wikipedia.org/wiki/Eadweard_Muybridge) recorded a rapid series of photographs of a racehorse belonging to Leland Stanford (then governor of California), in order to determine (allegedly for a bet) whether at any point all four legs were airborne.   Galloping horse, animated in 2006. Image: Public Domain. [Study from chrono graph](img/Muybridge01.jpg) In an article for Scientific American, Muybridge recommended readers to cut out his images of motion and paste them into a Zoetrope to recreate the illusion of motion. He later invented a device called the [zoopraxinoscope](http://en.wikipedia.org/wiki/Zoopraxiscope), to project up to 200 images in succession onto a screen, which was presented in 1880 to the California School of Fine Arts, thus becoming the father of motion pictures. "Recent scholarship has pointed to the immense influence of [Étienne Jules de Marey](http://en.wikipedia.org/wiki/%C3%89tienne-Jules_Marey) on Muybridge's work. Muybridge visited de Marey's studio in France and saw Marey's stop-motion studies of animals before returning to the U.S. to further his own work in the same area."  "Flying pelican captured by Marey around 1882."  This series is said to have influenced Duchamps' Nude Descending a Staircase:  Marcel Duchamp. Nude Descending a Staircase, No. 2 1912. Oil on canvas. The British [kinora](http://courses.ncssm.edu/gallery/collections/toys/html/exhibit05.htm), a kind of automated flip-book, preceded Edison's massively succesful [kinetoscope](http://en.wikipedia.org/wiki/Kinetoscope), with which viewers could watch sequences of around 50ft of celluloid film ribbon though a peep-hole.   Left: Kinora, Right: Kinetoscope Finally, the French Lumiere brothers invented the first celluloid camera-printer-projector device, the [Cinematographe](http://en.wikipedia.org/wiki/Cinematograph) in 1890s, opening the path for the motion picture industry. Note that this is not the first 'moving picture' device.   The cinématographe Lumière in projection mode, Image: Public Domain. ## Video - [Disneyland - 2.11 - The Story of the Animated Drawing - Part 1 of 4, 2'35" ~ 13'00"](https://www.youtube.com/watch?v=5xnQSLxJmMg)