Nehru arts and science college department of information technology



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NEHRU ARTS AND SCIENCE COLLEGE


DEPARTMENT OF INFORMATION TECHNOLOGY

E-LEARNING

CLASS: III B.Sc IT

SUBJECT: ANIMATION TECHNIQUES
Unit I

What is mean by Animation? – Why we need Animation – History of Animation - Uses of Animation – Types of Animation – Principles of Animation – Some Techniques of Animation – Animation on the WEB – 3D Animation – Special Effects – Creating Animation.

PART A


  1. What does the word animate mean?

Animate means ‘to give life to’.

  1. What is meant by tweening?

The process of drawing a number of frames in between the key-frames is called tweening.

  1. What is stop motion animation?

Animation that involves a model, which is changed small amounts at a time and then repeatedly photographed is called stop motion animation.

  1. Mention the uses of animation?

Animation is widely used in the entertainment industry. It is also at the heart of most computer games for making the graphics more realistic, exciting or engaging. Nowadays animation is increasingly used in education

  1. What are the two types of animation?

  1. Cel Animation and 2. Path Animation

  1. What is exaggeration?

Exaggerating an action can make it seem real. This is especially true in animation. Exaggerating the important elements makes them stand out and brings them closer to the viewer. An example is the case of the eyes of a character coming out of the sockets.

  1. What is flip book animation?

A flip book is a book with a series of pictures varying gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate, simulating motion or some other change.


  1. What is blue screening?

Bluescreening is a technique for shooting live action against a even colored blue background and then replacing the background by another image.

  1. What is morphing?

Morphing is the process of smoothly interpolating between two different images.

  1. What are the six steps of 3D animation?

Creation of 3D animation involves a number of steps: modeling, surface texture, lighting, camera, animating and rendering.

PART B

  1. What is mean by Animation?Why we need Animation?

Animate means ‘to give life to’. Animations are created from a sequence of still images. animation is the illusion of motion that is created by displaying a series of images or frames, each one slightly different from the last, over a brief period of time.

Animation can also involve a model, which is changed small amounts at a time and then repeatedly photographed. This type of animation is referred to a stop motion animation. Traditionally animation sequences are created by two types of artists: the lead artists or experts who draw those frames where major changes take place within the sequence, called key-frames, while the assistants draw a number of frames in between the key-frames, a process called tweening. Animation file formats like animated GIF and Flash SWF allow us to view animations on a computer or over the Internet.



  1. Explain the History of Animation.

In the later half of nineteenth century John Marey and Edward Muybridge developed devices that took sequences of photographs of moving objects, and used it to take pictures of galloping horses along a race track in California. In the beginning of the 20th century short animation films were created in which each frame was a separate drawing on paper. The integration between computer graphics and film was first done in the 1970s for creating special effects in feature films like 2001:A space odyssey. Throughout the 80s and 90s companies such as Industrial Light and Magic, Pacific Data Images and Pixar brought ever more sophisticated computer generated imagery to video and film, culminating in the release of ‘Toy Story’ by Pixar in 1995 the first completely computer generated animated feature film.


  1. What are the Uses of Animation?

Animation is widely used in the entertainment industry. It is also at the heart of most computer games for making the graphics more realistic, exciting or engaging. Nowadays animation is increasingly used in education as it provides an excellent way to explain dynamic processes which cannot be easily captured by video, e.g. movement of the pistons of an IC engine. A major use of animation in industrial and scientific applications is to visualize simulation of scientific phenomena, e.g. flight simulations for aircraft and guided missiles.

  1. Explain the Types of Animation.

Cel Animation

A cel animation is a term from traditional animation. Cel comes from the word Celluloid. Animation cels are generally layered, one on top of the other, to produce a single animation frame. To depict movement only a portion, typically the foreground cel, can be changed between frames without changing the background cel. (fig 1)(Refer page no342)

Path Animation

An image or collection of images together, called a sprite that moves as an independent object, like a flying bird. The sprite moves along a motion path, typically curved, called splines.

During playback of the animation, the vectors are used to generate the curved path on the screen and the sprite is made to move along the path, using other parameters like speed and duration to control its motion. Path animation is also known as Sprite animation. Usually path animation takes up less disk space to store compared to cel animation because of the vector compact vector representations. (fig 2)(Refer page no343)

2D vs 3D Animation

2D animation programs do not take into consideration the depth of objects and typically depict animated objects on flat surfaces. These are drawn taking into account two coordinate axes along X and Y directions. 3D animation monitors objects by considering space coordinates and usually involves modeling, rendering and adding surface properties, lighting and camera motions. These are more complex than 2D animation and have take into account 3 axes along X,Y and Z. (fig3)(Refer pageno343)


  1. Write a note on Animation on the Web

The WWW in the early 1990s, was initially created to serve hypertext documents but later on support for animated files was included in Web pages.

The uses of animations on the Web are some limitations,



  1. Typically Web based animations involve computer files that must be completely downloaded to the client machines before playback. This can take a long time depending on the file size. A way around this problem is streaming, which is capability of specially formatted animation files to begin playback before the entire file has been completely downloaded.

  2. Another problem with Web animation is that once the animation has been delivered to the user, the user must have the proper helper application or plug-in to display animation.

  1. Write a note on the Shockwave Format

Macromedia Director

Macromedia’s Shockwave technology for Director was one of the first animation plug-ins for browsers. Shockwave enables Director authors to publish interactive, multimedia content on the Web. To create Shockwave animations for the Web you will need the Director authoring program for Windows. Shockwave animations created on either Windows or Mac can play back in any browser that supports the Shockwave plug-in. To be played via the browser, the Director movie must be saved in the Shockwave format which uses the DCR file extension. It can be inserted in an HTML document using the tag.



PLUGINSPACE=”http:// www.macromedia.com/shockwave/download”>

To view the animation the user must have the Shockwave Player as a plug-in with the browser.

Macromedia Flash

Macromedia Flash animation sequences can be saved in the Shockwave format which uses the SWF extension and played back on a Shockwave Player. An SWF file contains most of the graphics and motion information as vectors which reduces its file size and can be used easily over the Internet in Web pages. SWF is an open format which means that anyone can implement players or application software to support SWF without paying royalties.


Client Pull Animation

In Client-Pull animation an HTML page gives the browser instructions to request and load another document automatically which contains the next frame of the animation. Client Pull is executed by a refresh command written into the tag of a HTML document. Client pull animation might be slow due to the need to load a whole page every time rather than a single cell of animation.



Server Push Animation

Server-push animation requires a CGI script that tells the server when to automatically serve a new document or image.



http://www.abc.com/animation.cgi>

When the browser recognizes the IMG tag it makes a single request to the server for a file. But rather than retrieving an image file, the HTML tag gives directions to a CGI script that runs the animation.



  1. What are the steps involved in 3D Animation?

Creation of 3D animation involves a number of steps: modeling, surface texture, lighting, camera, animating and rendering.

Modeling


It involves creation of 3D objects from 2D shapes. Two of the most common methods are lofting and lathing. Lofting is a process of changing a 2D shape into a 3D object by moving the shape along a specific direction. Lathing involves rotation of a 2D shape about an axis to create a 3D object.

Surface Texture

It involves imparting realistic appearances to the 3D models by applying textures over the object surface.e.g a wood texture applied to a flat surface for making a table.


Lighting

It involves placing the lights in the scene by specifying their intensities, direction and color.


Camera

It placements determine how the scene should look like. Movement of camera can be used to produce zooming and panning effects.



Animating

The object involves creation of key-frames and tweening to produce intermediate frames.



Rendering

It produces the final output file and needs specifying the file type, frame size, frame rate etc.



  1. Write a short note on Special Effects?

Atmospheric Effects

Many 3D computer graphics images have a distinctive crystal-clear quality and this is intended by the artist but sometimes it creates an appearance of unreality and falseness. In the real world the perceived colors of objects change depending on the distance of the objects from the viewer. This is produced by the scattering of the light rays by the tiny air molecules of the atmosphere. To address the problem, some higher end software packages offer techniques such as rain, snow, fog and haze. These permit us to define various atmospheric parameters. The program includes these parameters in the color calculations when it renders the final frame.


Particle Systems

Many phenomena like smoke, gas, steam, fire and clouds cannot be modeled easily as surfaces. The particle system technique found on many 3D system packages handles these types of phenomena that consist of masses of molecule sized particles rather than surfaces. Here you do not model individual surfaces rather you define the number of particles in the system. Defined to exist and move in a three-dimensional space, these particles which are too small to be seen individually, and will become visible only if present in sufficient numbers. When the rendering program processes the model information for a given frame, it looks at each pixel of screen space and calculates whether enough particles are present at that location to be visible. If so, pixels are colored appropriately and rendered.

In defining a particle system, you normally have several parameters under your control. One parameter is the number of particles; another is the color of the particles, which often can be animated as well. Rather than a generic particle system, most 3D systems offer specific particle systems with unique parameter sets to mimic natural phenomena. For e.g. a ‘cloud’ particle system may contain parameters for controlling the direction, the speed and randomness of movement, as well as a parameter for defining shape of a cloud.


PART C


  1. Explain the Principles of Animation.

The principles introduced in this section can be found in ‘Disney animation: The illusion of life’ by Frank Thomas and Ollie Johnston.

Squash and Stretch

e.g. Bouncing ball. An animation of a bouncing ball that does not change shape as it moves gives a lifeless, mechanical impression. To be more realistic the shape of the ball should be flattened as it strikes the ground and revert back to the original round shape as it rebounds back into the air. (fig 4)(Refer pageno346)



Anticipation

If the audience is not prepared for a sudden motion, the motion seems awkward and confusing, In life we usually prepare to act before we actually act and the animation should make this clear. e.g. before running away a character might brace its feet and look behind.



Staging

The concept of staging comes from theater and film. It means to arrange things in each frame so that the action is clear and easy to see. If too many things are happening in too many places, the audience would not know where to look. Staging means to give those characters emphasis and to integrate them with the background.



Follow-through and Overlapping Action

Like anticipation, follow through and overlapping action have to do with clarity. Follow through is the complement of anticipation. When you throw a Frisbee, for e.g., your arm continues its long arc after the Frisbee has left your hand. Including follow-through makes an action easier to see and more realistic. Anticipation and follow-through combine in overlapping action.


Slow-in and Slow-out

Slow in and Slow out means that there are more in between frames immediately before and after each stop, with fewer frames for faster action in between two stops. Slow in and Slow out contributes to realism because in the real world that is how the objects move. For e.g. When a person is in a position of rest seated in a chair, to begin moving and gather momentum takes a bit of time.


Arcs

Living things rarely move in perfectly straight lines. Our joints are hinges, and moving them describes an arc. The overall movement of characters in an animation should follow an arc as well. This is both more lifelike and more interesting visually.



Secondary Action

Secondary actions result from the main action. Anticipation and follow through are two examples, but there are others. Each part of a character might not move at the same rate. For e.g. a robe might trail behind a running character. Including secondary actions contributes to realism.



Timing

The speed of an action is an important way to show a character’s intent. Timing is also the most important way to indicate weight. A balloon is easy to move but soon slows down from the air. A boulder is hard to get moving but even harder to stop. The classic e.g is a character who walks off a cliff but does not fall until he or she looks down.



Exaggeration

Exaggerating an action can make it seem real. This is especially true in animation. Exaggerating the important elements makes them stand out and brings them closer to the viewer. An example is the case of the eyes of a character coming out of the sockets when he or she sees something startling.



Appeal

All the characters in an animation should have appeal. Appeal is visual as well as psychological. Characters that are visually intriguing are more likely to hold an audience’s attention than characters whose appearance is mundane or predictable.



  1. Explain Some Techniques of Animation

Introduction

Some techniques employed in building up an animation sequence, either in the traditional way or computer based. The objectives of these techniques are generally to improve the efficiency or reduce time-involvement or introduce some innovation over the basic cel or path animation schemes.


Onion Skinning

Onion-Skinning is a drawing technique borrowed from traditional cel animation that helps the animator create the illusion of smooth motion.This enables them to see previous and following frames while they are drawing the current frame. Onion skinning is an easy way to complete sequence of frames at a glance and to see how each frame flows into the frames befor and after.



Motion Cycling

Human and animal motion such as walking, running and flying, is mainly a repetitive action that is best represented by a cycle. A walk cycle requires from 8 to 12 frames. The sequence usually falls into two halves. The first half begins at an extreme(frames 1-2):the feet are at their farthest apart, with the back toe and front heel touching the ground. In the remainder of the first half (frames 3-4) the legs trade position. When the first left leg is forward, the right arm is forward, and vice versa. The second half of the cycle(frames 5-8)is simply a variation of the first half, but with arms and legs reversed. The finished walking character can be used as a moving cel, i.e. a sprite. (fig 5)(Refer pageno349)



Masking

A mask in a computer program is in a sense a model of the plastic masks it protects parts of a frame from effects of other editing tools. This technique can be used to make and animated object move “behind” the protected area. For e.g the frame of the TV is masked, so that the scrolling text do not appear in front of the frame, but is only visible within the TV screen.



Adding Sound

Sound is an important enhancement to moving images. Background music can evoke emotions. When sound matches the visuals for e.g, a door opening a or a person speaking, it is called synchronous sound. When sound is independent of the visuals, such as background music, it is called asynchronous sound.


Flip-book Animation

A flip book is a book with a series of pictures varying gradually from one page to the next, so that when the pages are turned rapidly, the pictures appear to animate, simulating motion or some other change. Flip books are often illustrated books for children. Flip books are essentially primitive form of animation. Like motion pictures, they rely on persistence of vision to create the illusion that continuous motion is being seen rather than a series of discontinuous images.

The flip book appeared in 1868, and was originally known as a kineograph.They were the first form of animation to employ a linear sequence of images In 1985, Thomas Edison invented a mechanized form called the mutoscope, which mounted the pages on a central rotating cylinder rather than binding them in a book.


Rotoscoping and Bluescreening

Rotoscoping was an early animation technique which enabled animators and video editors to trace the contour of objects on each frame of an animation and video sequence to create a silhouette called a matte. The technique was first used around 1914, to place live characters over synthetic backgrounds. Rotoscoping has been used as a tool for special effects in action movies.

Bluescreening is a technique for shooting live action against a even colored blue background and then replacing the background by another image. This is nowadays extensively used as chroma-keying using digital editing tools whereby the background color is selected by a selection tool and replaced by passing over with some other background.

Color Cycling

Color cycling allows you to change color of objects by cycling through a range of colors. The software provides smooth color transitions from one color to another. RGB color wheel is used to specifying an initial color, a clockwise or anti clockwise direction for changing colors.



Morphing

Morphing is the process of smoothly interpolating between two different images. For e.g, an individual’s face gradually transforming into the face of another person or even an animal. In the early days of films a morph would be achieved by cross-fading techniques , nowadays this is achieved more realistically using computer software. The popular science fiction film Terminator 2: Judgment Day uses this technique.



  1. Explain in detail about Creating Animation.

Introduction

Animation involves the production of a series of still images that when played back in quick succession, appear as continuously moving. This illusion is produced by a physiological characteristic of our eyes known as persistence of vision. In film a playback rate of twenty-four frames per second works well. In video the standard rate of playback is thirty frames per second. Thus, for producing a one hour animation on video 108000 frames would be required.

In the early days of animation, a technique was developed to produce animation frames more efficiently. First a master animator would draw the most important or keyframes of an animation sequence. Keyframes are those which correspond to some major action in the animation sequence. Then a number of less experienced assistant animators would draw the in-between frames between each pair of keyframes. This process is called tweening. Almost all 3D computer graphics animation systems are based on this key-framing and tweening approach. In a computer keyframing system the animator is the equivalent of the master animator. The animator sets up the keyframes, then instructs the computer to calculate the in-between frames. The computer thus, serves as an assistant to the human (master)animator.


Interpolations

A Key-frame based software system creates the in-between frames of an animation by interpolating the transformation values form one keyframe to the next. In fig.(a) An object is 10m away from the observer at key-frame 1(kf1) and 0m from the observer at key-frame 60(kf60). The animator specifies all the 9 transformation parameters to the software both at Kf1 and Kf60. The software then computes the values of the parameters from the frame 2 to frame 59 by interpolation. The simplest kind of interpolation called linear interpolation. All computer animation systems provide a capability called motion preview, which enables the animator to see the changes. The motion preview he/she may decide to change one of the keyframes and save it as a new keyframe overwriting the old keyframe.

(fig 6)(Refer pageno 361&362)

If your requirement is that the cube should move smoothly through various positions without any abrupt changes, then the solution is a spline interpolation. There is no abrupt changes in the curve the cube translates smoothly from one point to another over the entire length of the sixty frame animation.

In animation you often want some change to begin slowly and then increase in speed. Such changes are known as ease-in. The opposite of an ease-in is an ease-out, in which the value changes very quickly at first and the more slowly towards the end of the frame range. Combining an ease-in and an ease-out produces an interpolation called an ease-in-out (S shaped curve)in which the value changes slowly at first then more quickly and then slowly again.

Parameter-curve Editing

In a keyframe based animation system the most common way to define the movement and timing of an object is to transform the object manually until it looks right visually and then save each set of transformations as a keyframe.Using a system that allows parameter graph editing you can select control points that represents specific keyframes and pull them or down to change the value of the Sy parameter. In parameter curve editing systems it is normally possible to edit a curve in all the same ways that you might edit a curve for modeling purposes. For e.g., you might insert new control points into the curve, thereby changing the shape of the curve, as well as the animation controlled by the graph.

Most systems also allow you to select the type of interpolation used between any two control points. Any combination of interpolation types may be used between frames. This is useful when you want an element of your animation to change for a certain amount of time, but then to remain unchanging for another period of time. Most systems provide you with some ready way to lengthen or shorten a sequence of animation, effectively changing the timing to make an action slower or faster. This editing is called scaling the animation.


Hierarchical Animation

Many models are more complex than a simple one-piece object. Animating a hierarchical model is conceptually just an extension of the technique of animating a simple one piece model. For e.g. a table with 5 members, when rotating the table by a specific angle each of the members rotates about its own local origin. The result is not what is desired. The solution is to organize the model into a hierarchical structure. The whole table is at the top level of the structure and the separate elements are at the lower levels. Within such a hierarchy each element is called nodes, which are also called child nodes of the table. The table object however consists only of a transformation matrix but no geometry, because it is purely a logical grouping of several sub elements and has no shape of its own.

(fig 7)(Refer pageno364)

Inverse Kinematics (IK)

In some situations the guideline of the previous section, i.e., selecting each node of the hierarchy, transforming that node, and saving the transformation. Consider the simple arm model in one position and think about moving that model to another position. You know this intuitively and that is why you want to place the hand and let the joints follow, rather than individually rotating each joint in order to get the hand to a specific location. The technique that implements this approach is called inverse kinematics. Kinematics refers to the mechanical study of motion while inverse refers to the fact that the flow of transformations within the hierarchical model is calculated in the opposite direction to the normal calculations. While in the previous section the rotation of the table object(parent node) determined the final positions of the legs(child node), in this case the rotation of the hand(child node) determines the final position of the upper arm(parent node). In an Inverse kinematics model, the transformations applied to the lowest level, Hand determine the transformations of Lower Arm. The calculations of the transformations travel upwards through the hierarchy. The standard downward propagation of transformations is sometimes referred to as forward kinematics.



Upper Arm
( fig 8)


Upper Arm



Lower Arm




Lower Arm







Hand




Hand

Forward kinematics Inverse kinematics

An inverse kinematic model is often called a chain. Each joint or node is referred to as a link in the chain. The end point of the final link in an inverse kinematic chain is called the effector and the starting point of the first link in the chain is called the root of the chain. Inverse kinematics is applied to human and other animal bodies.

Motion paths

The concept of motion paths allows you to define a path that an object moves along. The path is drawn in space using the standard curve drawing techniques. This path usually called the motion path the object, represents the path along which the object will move. The animator indicates the object that should move along the path and specifies the number of frames over which the motion take place. For e.g. you draw a motion path and assign it to a cube beginning at frame 1 and ending at frame 100. If you use a standard linear interpolation then at frame 50 which represents half of the total time, the cube will be located halfway along the path.

(fig 9)(Refer pageno 366 & 367)

This moves the cube along the path at a constant rate of speed throughout the length of the animation. Most systems also provide a technique for controlling the rate of movement by adjusting the interpolation of a second curve, called a timing curve, which represents the rate of movement along the path. For e.g. by changing the linear curve to an ease-in interpolation curve, the animator specifies that the cube still follows the same motion path but doing so at a different rate of speed, moving slowly at first and then picking up speed covering a great distance in the final frames of the animation. Another importance that must be considered when animating an object along a motion path is the orientation of the object relative to the path. For e.g . animating a paper airplane along a motion path. Undoubtedly you want the nose of the airplane to stay on the path, i.e. to remain tangent to the curve. Some systems do this by default. Other systems by default always keep the object in the original orientation of the object as it moves along the path, and must be manually adjusted.


Shape Changes

Most 3D animation systems provide some way of reforming or deforming the shape of the surface of an object. In animating a flexible or changing surface you determine the positions of the points that define the surface(control points or vertices), save the positions of these points as a keyframe, reposition the surface-defining points, save a new keyframe and then ask the computer to interpolate the values between the two keyframes. The interpolated positions of the surface-defining points yield the in-between shapes of the object. For e.g, a shape change animation of a square transforming into a circle.

With a spline-based model, simple animations are not difficult, but complex animations might require a great deal of very careful selecting and moving of control points. A number of techniques developed to simplify the process of animating the surface defining points of a model. By moving few points of the controlling model, you move a large number of points of the original model. In one technique called lattice animation .Moving a few points on the lattice moves many associated points on the surface of the model and deforms the model. A second technique called axis deformation involves substituting one or more straight axes of the normal Cartesian coordinate system.

Camera Animation

Apart from animating objects over time, it is also possible to animate camera parameters, such as point of view from the scene is observed, over time. Most systems treat the camera as an object and allow you to manipulate it like translating or rotating. The settings of the camera are then saved as keyframe. The computer then interpolates the in-between camera positions for each frame that lies between the keyframes. Any of the parameters that define a camera location, direction, FOV, focal length normally can be animated with this keyframe approach. Cameras of graphics systems also permit you to animate the locations of the far and near clipping planes. This may be done to improve the Z-buffer rendering resolution of a scene.

Animating Lights and Surface Properties

Lights can be defined and placed in a virtual scene just like normal objects. It is possible to position a light, save that position as a keyframe, reposition it, save a new keyframe and then create the interpolated animation of the light moving from the the first position to the second. In addition it might be possible to rotate a spotlight or scale some specialized light such as an area light, the definition of which includes a specified size. In many systems we can animate the other parameters that make up the definition of light, like brightness, color, spread, etc. Some systems provide a default linear interpolation while other systems offer parameter curve editing capabilities for the animation of these lighting parameters.

You can also animate various surface characteristics of objects such as color, shininess, diffuseness, highlight color etc. For e.g. rotate a color texture map on a surface over time here the surface geometry and all other properties of the surface remain static. Only the rotation parameter of the texture map is animated.




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