Subject : multimedia

1. 
   What does the word ‘Animate’ mean?
   

1. 
   How is animation created?
   

1. 
   What is tweening?
   

1. 
   What are the different types of animation?
   

1. 
   What are MPEG 2 Video bit rates?
   

1. 
   What is the complementation of anticipation?
   

1. 
   What is flip book?
   

1. 
   Expand DFT.
   

1. 
   What are the three basic transformations?
   

1. 
   What is blue screening?
   

1. 
   What are the different types of animation?
   

1. 
   Cel Animation:
   

Animations cels are generally layered, one on top of the order, to produce a single animation frame. A frame consists of the background cel and the overlying cels and is like snapshots of the action at one instant time.

1. 
   Path Animation:
   

The sprite moves along a motion path typically curved called splines. This passes through the series of anchor points which the user can control to change the shape of the curve.

1. 
   2D vs. 3D Animation :
   

1. 
   Explain about computer assisted animations.
   

Computer assisted animation is also based on the key frame concept.

• 
  Frames are created in between by the animation program not by junior animators doing a lot of tedious work.
  
• 
  Cel based animation by placing the animated object on a time line
  
• 
  A play back head moves across the timeline to display frames one after the other.
  

1. 
   Explain about creating movement.
   

Two lines perpendicular to each other with distance marked along each line allow you to locate shapes accurately on a plane. This kind of system is called a coordinate system and the numbers that identify where a point is are called coordinates of a point.

Two lines drawn perpendicular to each other are called axes of the co ordinate system. The horizontal axis is usually called the X axis and the vertical axis is usually called Y axis. The point at which the axes cross is called the origin whose coordinate are (0, 0).

The coordinate of a point therefore involves three numbers instead of two. The origin has a coordinate of (0, 0, 0). Distance from the origin may be measured in any appropriate unit including pixels, inches, cm and points.

Three basic transformations are: Translation, Rotation and Scaling. Translation involves moving an object in straight lines in any direction on the screen. Rotation implies changing the orientation of an object by rotating it through some angles in the clock wise direction or counter clock wise direction. Scaling implies enlarging or shrinking whole or part of an object.

1. 
   Write a note on special effects.
   

Many 3D computer graphic images have a distinctive crystal-clear quality. In the real world the perceived colors of objects changes depending on the distance of the objects from the viewer. 3D computer rendering programs often have different handling this sort of atmospheric effect. To address this problem, some higher-end software package offer technique such as rain, snow, fog and haze. These permit you to define various atmospheric parameters interactively from menu windows.

In using an atmospheric rendering system you normally specify the color of the atmosphere and the distance at which that color completely overrides the color of objects. A technique provided by some system for handling this kind of irregularity involves what is known as a density map, a black and white picture that you create before you render frame.

Some system offer a variation of the density map technique over time where the vertical direction in the map denotes variation over a spatial axis and the horizontal direction of the map as variation over time.

Many phenomena like smoke. Gas, steam, fire and clouds cannot be modeled early 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.

One parameter is the number of particle; another is the color of the particle, which often can be animated as well. E.g.: Fire particle often can be animated well; ‘cloud’ particle system may contain parameter for controlling the direction, A ‘Stream’ particle for defining a moving stream of water particle. The most common of this function is an explosion in which each surface is broken into many small surfaces which expand outward in an exploding pattern.

1. 
   Give short notes on Compression.
   

It is extremely difficult working with such huge files mainly because of two reasons:

• 
  Due to their huge sizes storage requirements increases rapidly with multiple such media files thereby increasing the cost. During a multimedia development work one can quickly run out of disk space.
  
• 
  Even if there is adequate storage space, such files require a large data transfer rate that may be beyond the capabilities of both the processor and hard disk. Foe E.g.: to play back an audio file, the disk and processor have to process about 1.4 million bits of data per second.
  

1. 
   Explain about MPEG2 – Audio.
   

The MPEG-2 audio standard was designed for applications ranging from digital HDTV television transmission to internet downloading. It uses lower sampling frequencies providing better sound quality at low bit rates. The MPEG-2 standard encompasses the MPEG-1 standard using the same coding and decoding principles as MPEG-1.

1. 
   MPEG-2 BC:
   

1. 
   MPEG-2 AAC:
   

1. 
   Explain about MPEG – 2 Video.
   

The MPEG was developed to provide video quality not lower than and up to HDTV quality. Its target bit rates are 2 to 15 Mbps and it is optimized at 4Mbps.

The standard provides for four levels of video resolutions.

For each of the above four levels, MPEG-2 provides for five profile: Simple, Main, Spatial resolution, Quantization accuracy, and high. The decoders for a given profile would be able to decode all the lower profiles that have been defined for the level.

The coding scheme is similar to MPEG-1 the main difference being that instead of progressive scanning, interlaced scanning is used. There are two alternatives: field mode and the frame mode. In field mode DCT blocks are generated from a field and are used where large amount of motion is present, capitalizing on the shorter time interval to generate a field. In frame mode DCT a block are derived from a frame and is used for slower motion, using a longer time interval to generate a frame.

This form the basis of the ATV (Advanced Television) standard for HDTV in North America. It uses a 16:9 aspect ratio with resolution of 1280 by 720.

This forms the basis of the DVB (Digital Video Broadcast) standard for HDTV in Europe. It uses a 4:3 aspect ratio and defines a resolution of 1440 by 1152(1080 visible). This is exactly twice the resolution of low definition PAL format of 720 by 576.

This forms the basis of the MUSE (Multiple sub-Nyquist Sampling Encoding) standard for HDTV in Japan and rest of Asia. It uses a 16:9 aspect ratio with a resolution of 1920 by 1035.

1. 
   Write about principles of animation.
   

Traditional hand drawn animation has a set of principles of its own. The goal for the Disney animation was to create ‘the illusion of life’.

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 flatted as it strikes the ground and revert back to the original round shape as it rebounds back into the air.

(Squash and stretch)

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.

The concept of staging comes directly 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.

Follow through is the complement of anticipation. Including follow through makes an action easier to see and more realistic. Anticipation and follow through both combine in overlapping action. Overlap contributes to the continuity of a scene.

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. They contribute to realism because in the real world that is how the object moves

The overall movement of characters in an animation should follow an arc as well.

Secondary actions results from the main action. Each part of a character might not move at the same rate. For example, a robe might trail behind a running character. Including secondary actions contributes to realism.

Holding an important moment of scene is just as important as getting the proper speed. A hold gives the audience time to recognize what is going on. The classic example is a character that walks off a cliff but does not fall until he or she looks down.

It is an action can make it seem real. This is especially true in animation. The important element makes them stand out and brings them closer to the viewer. An example is the case of the eye of a character coming out off the sockets. When he or she seems something startling.

All the characters in an animation should have appeal. It 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 about some techniques of animation.
   

The objective of these techniques is generally to improve the efficiency or reduce tome involvement or introduce some innovation over the basic cel or path animation schemes.

It is drawing technique borrowed from traditional cel animation that helps the animator create the illusion of smooth motion. It is an easy way to complete sequence of frames at a glance and to see how each flows into the frames before and after.

Human and animal motion such as walking, running and flying is mainly a repetitive action that is best represented by a cycle. The first half begins at an extreme, the feet are at their farthest apart, with the back toe and front heal touching the ground. In the reminder of the first half the legs trade position. So do the arms but when the left leg is forward the right arm is forward and vice versa the second half of the cycle is simply a variation of the first half but with arms and legs reversed.

A mask in a computer program is in a sense a model of the plastic masks- it process parts of a frame from effects of other editing tools. The technique can be used to make an animated object move “behind” the protected area. In fig 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.

Stay tune

to this channel

Stay tuned

(Masking)

Adding Sound:

Sound is an important enhancement to moving images. Background music can evoke emotions. Sounds that arise from the action being viewed can clarify what is happening and create an effect of realism.

A flip book is a book with series of pictures varying gradually from one page to the next, so that when the pages are tuned rapidly, the pictures appear to animate, simulating motion or some other change. Flip book are not always separate books, but may appears an added feature in ordinary books or magazines, often in the page corners. Flip book are essentially a primitive form of animation.

It 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 traced contour would then be replaced by something else to produce a special visual effect.

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

Color Cycling:

It allows you to change color of object by cycling through a range of colors. The software provides smooth color transition from one color to another. In an RGB color wheel this can be done by specifying an initial color, a clockwise or anti-clockwise direction for changing colors and the total time duration for complete rotation over the wheel.

Morphing is the process of smoothly interpolating between two different images. When played back it appears that the first image gradually and seamlessly changes into the second images.

1. 
   Write about animation on the web.
   

The World Wide Web developed in the early 1990s was initially created to serve hypertext documents but later on support for animated files was included in web pages. A way around this problem is streaming, which is the capability of specially formatted animation files to begin playback before the entire file has been completely downloaded.

1. 
   Macromedia Director:
   

Macromedia’s shockwave technology for director was one of the first animations plug-ins for browsers. Director is a popular 2D animation and interactive multimedia authoring tool which is used in CD-ROM publishing broadcast videos and film. To create shockwave animation for the Web you will need the director authoring program for Windows.

Director movie must be saved in the shockwave format which uses the DCR files extensions. It can then be inserted in an HTML document using the tag

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

1. 
   Macromedia Flash:
   

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 instruction to request load another document automatically which contains the next frame of the animation. Client Pull is executed sequence the browser reads this header information which instructs it to keep of the time.

The META tag with the refresh command does two things first, it includes the time before the next page request is sent or the same page reloads. Second, it indicates a location, typically a URL, from where the next page is to be loaded, here page2.html. Client pull animation might be slow due to the need to load a whole page everything rather than a single cell of animation.

Server-Push Animation:

It requires a CGL (Common Gateway Interface) Script that tells the server when to automatically server a new document or images. The HTML source code for a server push animation looks like this:

IMG SRC = http://www.abc.com/animation.cgi>

When the browser recognizes the IMG tag it makes a single request to the server for a file. The CGI script sends a series of images to the client as if it was transferring a single file.

1. 
   Explain in detail about rendering algorithm.
   

1. 
   Ray Casting Algorithm:
   

A Rendering algorithm therefore is the procedure that a particular program uses to calculate a picture. Most rendering algorithm in software package use a general approach called Scan-Line Rendering. To determine what color a given pixel should filling common approach is a process called Ray Casting.

The eye then follows the ray until the ray either hits an object or exists from the viewable world. If the ray hits an object the program calculates the color of the object at the point where it has been hit.

(Ray Casting)

1. 
   Shading Algorithm:
   

Shading Algorithm is used to calculate the shading of a surface. Rendering each flat surface with only one color gives object a faceted look and therefore is called faceted Shading. In order to calculate the color of a given surface any shading algorithm must know whether the surface faces towards or away from light.

According the surface will appear lighter or darker. In order to determine the direction in which the surface faces, computer graphics programs employ use the surface normal. A surface normal is a line perpendicular to a surface at a given point on that surface and is represented by an arrow coming off the surface.

(Shading)

Several shading algorithm have been developed for rendering polygonal surface so that they look smooth. As a group they are referred to as a smooth shading algorithm, and these work by calculating the average of the normal at a given vertex and then calculating the color at each vertex based on the averaged surface normal at that vertex.

1. 
   Z-buffer Algorithm:
   

To presort objects by depth can be very time consuming particularly with a scene involving a large number of objects because each polygon of each object has to be sorted by depth. An alternative solution to this problem is known as the Z-buffer Algorithm.

When ray is a cast through a pixel, the ray light hit any of the several objects that lie in its path. When ray hits a pixel its z-value is looked from the Z- buffer and store.

1. 
   Ray Tracing Algorithm:
   

A different category of rendering algorithm called ray tracing addresses this problem by dealing with the entire object in a scene simultaneously. As with the ray casting technique, a ray is projected from the eye through the pixel and into the scene and hits the first surface. If the surface has been defined as somewhat reflective the ray bounces off it and hits the second object which might have been defined as partially reflective and partially transparent.

Consequently most ray casting programs ask you to define the maximum number of bounces that each ray should follow. This is called the depth of the ray tracing. The larger the depth, the more accurate but also more time- consuming the rendering.

1. 
   Polygon Subdivision:
   

• 
  A patch need far fewer polygon than do other sections
  
• 
  Flat areas of the patch, only a few polygon are necessary to produce a good approximation
  
• 
  Where the curvature of a patch changes abruptly
  
• 
  A lot of polygons are required to make the rendering look smoothly curved.
  

1. 
   Aliasing:
   

Anti aliasing consists of selectively blurring certain pixel along the aliased edge of a rendered surface. Some high end system provides you with parameters for controlling the quality of the anti aliasing.

Temporal aliasing is a problem that occurs when the object are moving very quickly. Sometimes the placement of an object within the frame changes drastically from frame to frame and this produces a jerky effect when you play the animation back. Motion blur, involves rendering fast moving objects with a slight blurring at each frame.

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