Animation

Contents

1 History 2 Early Examples 3 3D ani ma tion

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Cel-shaded animation Morph target animation Skeletal animation Motion capture

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Other animation techniques

Animation History There is no single person who can be considered the "creator" of the art of film animation, as there were several people doing several projects which could be considered various types of animation all around the same time. Georges Méliès was a creator of special-effect films; he was generally one of the first people to use animation with his technique. He discovered a technique by accident which was to stop the camera rolling to change something in the scene, and then continue rolling the film. This idea was later known as stop-motion animation. Méliès discovered this technique accidentally when his camera broke down while shooting a bus driving by. When he had fixed the camera, a hearse happened to be passing by just as Méliès restarted rolling the film, his end result was that he had managed to make a bus transform into a hearse. This was just one of the great contributors to animation in the early years. J. Stuart Blackton was possibly the first American filmmaker to use the techniques of stop-motion and hand-drawn animation. Introduced to filmmaking by Edison, he pioneered these concepts at the turn of the 20th century, with his first copyrighted work dated 1900. Several of his films, among them The Enchanted Drawing (1900) and Humorous Phases of Funny Faces (1906) were film versions of Blackton's "lightning artist" routine, and utilized modified versions of Méliès' early stop-motion techniques to make a series of blackboard drawings appear to move and reshape themselves. 'Humorous Phases of Funny Faces' is regularly cited as the first true animated film, and Blackton is considered the first true animator.

Early Examples The bouncing ball animation (below) consists of these 6 frames.

This animation moves at 10 frames per second. Animation is the rapid display of a sequence of images of 2-D or 3-D artwork or model positions in order to create an illusion of movement. It is an optical illusion of motion due to the phenomenon of persistence of vision, and can be created and demonstrated in a number of ways. The most common method of presenting animation is as a motion picture or video program, although several other forms of presenting animation also exist. Animation can sometimes refer to a way of activating a community, i.e. 'animating' the users. This means actions which encourages users to interact with a given service and is connected to moderation.

3D animation Digital models manipulated by an animator. In order to manipulate a mesh, it is given a digital armature (sculpture). This process is called rigging. Various other techniques can be applied, such as mathematical functions (ex. gravity, particle simulations), simulated fur or hair, effects such as fire and water and the use of Motion capture to name but a few. Many 3D animations are very believable and are commonly used as special effects for recent movies. Examples: The Incredibles, Shrek, Finding Nemo, Flatland 3D animation terms • • • •

Cel-shaded animation Morph target animation Skeletal animation Motion capture

Cel-shaded animation

Object with a basic cel-shader (also known as a toon shader) and border detection. Cel-shaded animation (also called cel-shading or toon shading) is a type of nonphotorealistic rendering designed to make computer graphics appear to be handdrawn. Cel-shading is often used to mimic the style of a comic book or cartoon. It is a somewhat recent addition to computer graphics, most commonly turning up in console video games. Though the end result of cel-shading has a very simplistic feel like that of hand-drawn animation, the process is complex. The name comes from the clear sheets of acetate, called cels, that are painted on for use in traditional 2D animation, such as Disney classics.

Pr ocess The cel-shading process starts with a typical 3D model. Where cel-shading differs from conventional rendering is in its use of non-photorealistic lighting. Conventional (smooth) lighting values are calculated for each pixel and then mapped to a small number of discrete shades to create the characteristic flat look. Black "ink" outlines and contour lines can be created using a variety of methods. One popular method is to first render a black silhouette, slightly larger than the object itself. Backface culling is inverted and the back-facing triangles are drawn in black. To dilate the silhouette, these back-faces may be drawn in wireframe multiple times with slight changes in translation. Alternately, back-faces may be rendered solid-filled, with their vertices translated along their vertex normals in a vertex shader. After drawing the silhouette, back-face culling is set back to normal to draw the shading and optional textures of the object. Finally, the image is composited via Z-buffering, as the back-faces always lie deeper in the scene than the front-faces. The result is that the object is drawn with a black outline and interior contour lines. The Utah teapot rendered using cel-shading:

1. The back faces are drawn with thick lines 2. The object is drawn with a basic texture 3. Shading Steps 2 and 3 can be combined using multi-texturing (see texture mapping). Another outlining technique is to use 2D image-processing. First, the scene is rendered (with cel-shading) to a screen-sized color texture:

Then, the scene's depth and world-space surface normal information are rendered to screen-sized textures:

A Sobel filter or similar edge-detection filter is applied to the normal/depth textures to generate an edge texture. Texels on detected edges are black, while all other texels are white:

Finally, the edge texture and the color texture are composited to produce the final rendered image:

As with most image-processing techniques, the performance penalty for this method is not affected by scene complexity.

List of cel-shaded media Video games Some of the more prominent games that have featured cel-shaded graphics:

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Breath of Fire: Dragon Quarter Cel Damage Crackdown Crazyracing Kartrider Dark Cloud 2 Fear Effect Gungrave series Harvest Moon: Save the Homeland Jackie Chan Adventures Killer7 Klonoa 2 The Legend of Zelda: Phantom Hourglass Mega Man X Command Mission Metal Gear Acid 2 Samurai Legend Star Wars: Clone Wars Steamboy Silver Surfer Skyland Sonic X Team Galaxy The Iron Giant

Morph target animation Morph target animation (or per-vertex animation) is a method of 3D computer animation that is sometimes used as an alternative to skeletal animation. Morph target animation is stored as a series of vertex positions. In each keyframe of the animation, the vertices are moved to a different position. Depending on the renderer, the vertices will move along paths to fill in the blank time between the keyframes or the renderer will simply switch between the different positions, creating a somewhat jerky look. The former is used more commonly. There are advantages to using morph target animation over skeletal animation. The artist has more control over the movements because he or she can define the individual positions of the vertices within a keyframe, rather than being constrained

by skeletons. This can be useful for animating cloth, skin, and facial expressions because it can be difficult to conform those things to the bones that are required for skeletal animation. However, there are also disadvantages. Vertex animation is usually a lot more timeconsuming than skeletal animation because every vertex position would have to be calculated. (3D models in modern computer and video games often contain something to the order of 4,000-9,000 vertices.) Also, in methods of rendering where vertices move from position to position during in-between frames, a distortion is created that doesn't happen when using skeletal animation. This is described by critics of the technique as looking "shaky". On the other hand, this distortion may be part of the desired "look". Not all morph target animation has to be done by actually editing vertex positions. It is also possible to take vertex positions found in skeletal animation and then use those rendered as morph target animation. Sometimes, animation composed in one 3D application suite needs to be transferred to another, as for rendering. To avoid export issues, native animation formats will often be converted to morph target animation. This is sometimes necessary due to the different ways 3D application suites implement bones and other special effects.

Skeletal animation

Skeletal animation, sometimes referred to as rigging, is a technique in computer animation, particularly in the animation of vertebrates, in which a character is represented in two parts: a surface representation used to draw the character (called the skin) and a hierarchical set of bones used for animation only (called the skeleton). This technique is used by constructing a series of 'bones'. Each bone has a three dimensional transformation (which includes its position, scale and orientation), and an optional parent bone. The bones therefore form a hierarchy. The full transform of a child node is the product of its parent transform and its own transform. So moving a thigh-bone will move the lower leg too. As the character is animated, the bones change their transformation over time, under the influence of some animation controller.

Each bone in the skeleton is associated with some portion of the character's visual representation. In the most common case of a polygonal mesh character, the bone is associated with a group of vertices; for example, in a model of a human being, the 'thigh' bone would be associated with the vertices making up the polygons in the model's thigh. Portions of the character's skin can normally be associated with multiple bones, each one having a scaling factors called vertex weights, or blend weights. The movement of skin near the joints of two bones, can therefore be influenced by both bones. For a polygonal mesh, each vertex can have a blend weight for each bone. To calculate the final position of the vertex, each bone transformation is applied to the vertex position, scaled by its corresponding weight. This algorithm is called matrix palette skinning, because the set of bone transformations (stored as transform matrices) form a palette for the skin vertex to choose from.

Motion capture Motion capture, motion tracking, or mocap is a technique of digitally recording movements for entertainment, sports, and medical applications. In the context of filmmaking (where it is sometimes called performance capture), it refers to the technique of recording the actions of human actors, and using that information to animate digital character models in 3D animation.

A dancer wearing a suit used in an optical motion capture system

The procedure

In the motion capture session, the movements of one or more actors are sampled many times per second. High resolution optical motion capture systems can be used to sample body, facial and finger movement at the same time. A motion capture session records only the movements of the actor, not his/her visual appearance. These movements are recorded as animation data which are mapped to a 3D model (human, giant robot, etc.) created by a computer artist, to move the model the same way. This is comparable to the older technique of rotoscope where the visual appearance of the motion of an actor was filmed, then the film used as a guide for the frame by frame motion of a hand-drawn animated character. If desired, a camera can pan, tilt, or dolly around the stage while the actor is performing and the motion capture system can capture the camera and props as well. This allows the computer generated characters, images and sets, to have the same perspective as the video images from the camera. A computer processes the data and displays the movements of the actor, as inferred from the 3D position of each marker. If desired, a virtual or real camera can be tracked as well, providing the desired camera positions in terms of objects in the set. A related technique match moving can derive 3D camera movement from a single 2D image sequence without the use of photogrammetry, but is often ambiguous below centimeter resolution, due to the inability to distinguish pose and scale characteristics from a single vantage point. One might extrapolate that future technology might include full-frame imaging from many camera angles to record the exact position of every part of the actor’s body, clothing, and hair for the entire duration of the session, resulting in a higher resolution of detail than is possible today. After processing, the software exports animation data, which computer animators can associate with a 3D model and then manipulate using normal computer animation software. If the actor’s performance was good and the software processing was accurate, this manipulation is limited to placing the actor in the scene that the animator has created and controlling the 3D model’s interaction with objects.

Other animation techniques •

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Drawn on film animation: a technique where footage is produced by creating the images directly on film stock, for example by Norman McLaren and Len Lye. Paint-on-glass animation: a technique for making animated films by manipulating slow drying oil paints on sheets of glass. Pinscreen animation: makes use of a screen filled with movable pins, which can be moved in or out by pressing an object onto the screen. The screen is lit from the side so that the pins cast shadows. The technique has been used to create animated films with a range of textural effects difficult to achieve with traditional cel animation. Sand animation: sand is moved around on a backlighted or frontlighted piece of glass to create each frame for an animated film. This creates an interesting effect when animated because of the light contrast.

Name:- Punyarup Nayak Roll no:- 710551 Branch:- computer sc.(3rd sem)

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