Cartoons and animation films D. Indumathi (The Institute of Mathematical Sciences, Chennai) All of you must have seen cartoons in books, on TV or in a movie. The very first cartoons appeared in Punch magazine more than 150 years ago. They were simply funny art pictures that also made you think. Soon, single cartoon drawings gave way to entire cartoon strips or cartoon series like Phantom or Mandrake the magician. Here, a full story was narrated through the medium of drawings, with very little text or writing. Amar Chithra Katha books are such picturised narrations. When the medium of cinema was discovered, cartoons were also transformed. Instead of a cartoon strip, the story developed through moving cartoon characters. Since these pictures moved and acted in a life-like manner, these cartoon characters were called animations. Persistence of vision Animations work because of a very important property of our brain called persistence of vision. The retina of the eye records images. These images are analysed and interpreted by the brain and that is how we "see". The cells in the retina are activated by light falling on it. What happens then is a chemical reaction when this information is processed. Since the chemical reaction happens rather slowly, the retina retains the information about the image for about 1/10th of a second. If the images that fall on the eye are changing faster than this rate, the brain is unable to process them separately. So the separate images appear as a continuously changing or moving set. This gives the appearance of motion so that the set of static images appear to be animated. The bird in the cage A nice example is to draw a bird on one side of a circular card-board sheet and a cage on the other side. Pierce two holes at either end of the sheet and loop two strings through the holes. Hold the ends of the strings loosely with your hands and spin the card-board several times so that the string gets twisted around itself. Now jerk the string tight and watch while the string unwinds. As the string twirls, the card-board rotates very fast and it appears as if the bird is in the cage. This game was invented nearly 200 years ago and is called the thaumatrope. An animation, therefore, has a sequence of (usually two-dimensional, flat) images changing at a rate of 10 per second or even more. Each image is called a frame. The images are photographed in front of a (usually) still background. If the frame speed is low, a flicker is seen when the movie is viewed. At a higher speed, a smooth animation results. If the frame change is too fast, the image gets blurred: you may have noticed this when a camera tracks a very fast ball in cricket. Modern movies usually show 24 frames a second. Unless the cartoon characters are moving very fast, each drawing is repeated for two frames, so that there are only 12 drawings per second. Cheap animations cartoons even show 6 or 8 drawings per second. How to make a animation A simple example of animation is the flip-book. As the name suggests, it is a book which you hold firmly with one hand, while flipping the pages very fast using the other hand. Each page has a hand-drawn picture. A simple sequence is that of the bouncing ball shown in the six frames below. If you draw this sequence several times on small sheets of paper and hold or staple the sheets together, you will have a flip book. When you flip through the pages, the ball appears to smoothly bounce up and down. The basic idea is that each picture is got by changing the previous picture in a small, controlled manner. Here the position of the floor remains the same while the ball is in a slightly different position each time. If you have access to Internet on a computer, you can see the final bouncing ball animation at http://en.wikipedia.org/wiki/Animation. Similarly, a person (or animal) walking can be shown by moving the position of the arms and legs by small amounts in each successive drawing. As you can imagine, animation, especially, hand-drawn animation is very laborious and pain-staking. A flip-book containing hand-drawn images with a very beautiful theme was shown in the movie Taare Zameen Par (2007). Old cave paintings exist where animals are shown with multiple legs in superimposed positions. This appears to be an attempt to convey the perception of motion. Since only small changes occur between two drawings, such animations are created by having the chief artist draw the major positions. In the case of a person waving a hand, for example, the key frames are the person standing with hand down, then half-way up, then fully up, waving first to one side and then to the other. Then a junior artist will draw the "in-between" frames where small changes in the hands will move it from the "down" position to the half-way one, and so on, in order to obtain a smooth motion. This is called "in-betweening" or "tweening". A lot of the labour involved in cartoon animation is in in-betweening. Computer animation has helped a lot here. The creator of film and stop-motion animation Several people started trying out special effects in films. Georges Melies was one of them. He discovered a technique by accident called stop-motion animation. Once his camera broke down while shooting a bus driving by. When he had fixed the camera, a horse happened to be passing by just as Melies restarted rolling the film. When the film was played, it appeared that the bus had transformed into a horse! There are many different types of stop-motion animation, usually named after the type of media used to create the animation. For example, clay animation uses figures of clay, puppet animation uses puppets, cutout animation moves 2-d images over paper or cloth background, and graphic animation users photos and drawings to create the illusion of motion. J. Stuart Blackton was possibly the first American filmmaker to use the techniques of stop-motion and hand-drawn animation. He was introduced to film-making by Thomas Edison (who invented the light bulb). His film, "Humorous Phases of Funny Faces" (1906), is regularly cited as the first true animated film, and Blackton is considered the first true animator. Rotoscoping Here live-action movement is traced frame by frame. The figure (courtesy Wikipedia) shows a set of 16 photos of a racing horse galloping, taken by Eadweard Muybridge (1887, Philadelphia). Notice that there is very little change between successive images. (You can cut out these images and hold them together as a flip-book.) Such film can be used as a basis for character animation (as in most Disney films). This process was patented by Max Fleischer in 1917. Computer animation Examples of traditionally animated feature films include Pinocchio (1940) and Animal Farm (1954). Traditional animated films which were produced with the aid of computer technology include The Lion King (US, 1994) and Spirited Away (Japan, 2001). However, nowadays the animation is created completely digitally on the computer. The characters and scenes are created as well as moved through the use of computer programs. Both two-dimensional (2-D) and three-dimensional (3-D) graphics are used. Computer animation is also called CGI (computer-generated imagery or computer-generated imaging), especially when used in films. The technique used is essentially the same as stop-motion animation, except that it is done with a computer. The computer image Depending on the complexity needed, key positions of an image are identified by the programmer or animator. Both 2-D and 3-D images are used. For instance, if it is a human being, it is first identified by a basic "skeleton". This skeleton is not visible in the final animation. It is simply used to make sure that the human does not "come apart" or lose shape when it is moving. It also determines what parts can move to show motion or expression. Then its hands and legs, neck, mouth, are highlighted as movable parts or segments. Even hair and clothes are moved to make it more life-like. So the skeleton does not only mean the bones: it includes all those parts that the animator may wish to move. The position of each segment of the skeletal model is defined by animation variables, or Avars. By changing the values of these Avars, the character shows movements of many different kinds. On the other hand, if any part of the image is not part of the skeleton, it cannot be moved at all. Simple computer animation uses stick-like figures where only hands and legs may move and there is no change in facial expression. In commercial animated movies, every image has hundreds of Avars. The character "Woody" in Toy Story for example, uses 700 Avars, including 100 Avars in the face. This allowed the character to show many moods or facial expressions as well as motion by changing the values of Avars over time. Key framing The main job of an animator is to generate the correct Avar values to obtain realistic motion. These Avars are set at strategic points (frames) in time. The computer interpolates between these frames; that is, the computer itself does the in-betweening. This process is called key framing. The main advantage here is that the in-betweening is done automatically by computer programs and that reduces a lot of work. The computer just does the work of a traditional animator. Motion capture This is a new method in which live action is used and is not just an extension of traditional animation. A real performer acts out the scene that is supposed to be animated. His or her motion is recorded to a computer using video cameras and markers. The markers are usually at important positions on the face or limbs where there is movement or show of emotion due to facial expression. This information is used to move the corresponding character that is eventually animated by the computer. For example, in the 2006 film Pirates of the Caribbean: Dead Man's Chest, actor Bill Nighy provided the performance for the character Davy Jones. As seen in the bottom picture, the parts where there are white dots on the actor's face and body are recorded as 3-D markers. The movements of these positions are used to create the computer animated character of Davy Jones, as shown in the middle picture. Finally, special effects are added on to the character's face for a more "realistic" effect. Even though Nighy himself doesn't appear in the film, the movie benefited from his performance by recording his posture, facial expressions, etc. Thus motion capture is appropriate in situations where believable, realistic behavior and action is required. Rendering Finally, the animation is rendered. In computer animation, it is not easy to have an object move over a background, as is normally done in traditional animation. This is because the computer has to be "told" through a program, what the properties of the object are. For instance, if it is transparent it should not hide the background when it moves in front of it. If it is opaque, it will not only hide the background but also cast a shadow depending on the source of light in the image. For movie animations, several images (frames) must be rendered, and stitched together since there may be many images in one scene. One such beautiful example of a completely computer-generated image is shown on the back cover. The major visible features include transparency, texture, shadows, shading due to position of light sources, and depth of field. All these are possible due to rendering. Tracing every ray of light in a scene would be impractical and would take gigantic amounts of time. So, there is a search for efficient programs or algorithms to do rendering. A number of different techniques are available to obtain a final image. Computer software and hardware Computer animation can be created with a computer and animation software. Some examples of animation software are: Amorphium, Art of Illusion, Poser, Ray Dream Studio, Bryce, May, Blender, TrueSpace, Lightwave, 3D Studio Max, SoftImage XSI, Alice, and Adobe Flash (2D). 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. Movie animation needs a high quality that would take tens to hundreds of years to create on a home computer. Very powerful networks of computers called farms are used for this purpose. Video games Rendering is also used for 3D video games where the scene keeps changing depending on how the game is played. Here rendering is needed in real-time unlike in an animation movie scene where the image is obtained once and for all in a unqiue way. Here it is difficult to insist that the computers be very fast or powerful since games are played on ordinary computers. So the program is speeded up by the use of of graphics cards with 3D hardware accelerators (OpenGL and DirectX are popularly used.) This ensures that the scene changes correctly on-line as the game is played. The animated object below was generated in Perl OpenGL. Architecture Architects use services from animation companies to create 3-dimensional models for both the customers and builders. It can be more accurate than traditional drawings. Architectural animation can also be used to understand the building in relation to the environment and its surrounding buildings. The future Currently, most computer-animated movies show animal characters (Finding Nemo), fantasy characters (Shrek, Monsters Inc.), anthropomorphic machines (Cars, Robots) or cartoon-like humans (The Incredibles). A computer-generated attempt to show realistic-looking humans is still an open problem. Perhaps you will be the one do solve this problem! Adapted from Wikipedia, the free Encyclopedia