CGMB 324: MULTIMEDIA SYSTEM DESIGN

Chapter 06: Multimedia Element IV - Animation

Objectives

Upon completing this chapter, you should be able to:To identify the terms and concept related to animationTo define animation and describe how it can be used in multimedia systemsTo understand some of the common animation techniques

Principles of Animation

Animation

Animation = An illusion of movement created by sequentially playing still image frames with different movements at the general rate of 15 - 30 fps (frames per second)

This animation moves at 10 frames per second.

This animation moves at 2 frames per second. At this rate, the individual frames should be discernible

Animation

These frames may be generated by computers, or by photographing a drawn or painted image, or by repeatedly making small changes to a model unit (claymation and stop motion), and then photographing the result with a special animation camera.

When the frames are strung together and the resulting film is viewed, there is an illusion of continuous movement due to the phenomenon known as persistence of visionpersistence of vision..

Generating such a film tends to be very labour intensive and tedious, though the development of computer animation has greatly sped up the process.

The animations shown before consist of these 6 frames.

How Animation Works?

It is believe that animation is possible because of

a biological phenomenon known as persistence of visionpersistence of vision An object seen by human eye remains

chemically mapped on the eye’s retina for a brief time after viewing

a psychological phenomenon called phi.phi. Human’s mind need to conceptually complete

the perceived action i.e. translating the action

Still images are flashed in sequence to provide the illusion of animation

How Animation Works?

Combination of these two (persistence of vision + phi) make it possible for a series of images that are changed very slightly and very rapidly, one after another, to seemingly blend together into a visual illusion of movement.

E.g. a few cells or frames of rotating logo, when continuously and rapidly changed, the arrow of the compass is perceived to be spinning.

Morphing – process of transforming one image into another via a series of frames

How Animation Works?

The speed of the image changes is called the frame rate.

Movie/Film is typically delivered at 24 – 30 frames per second (fps)

Computer animations can be effective at 12 12 to 15 frames per secondto 15 frames per second

How Animation Works?

To animate can be thought of as, “to bring to life”

Animation includes time varying positions (motion dynamics), shape, color, transparency, structure and texture of an object (update dynamics), and changes in lighting, camera position, orientation and focus.

Animation Techniques

Traditional animation, sometimes also called cel cel animationanimation or hand-drawn animation, is the oldest and historically the most popular form of animation.

Traditional animation began with each frame being painted and then filmed.

Cel animationCel animation, developed by Bray and Hurd in the 1910s, sped up the process by using transparent overlays so that characters could be moved without the need to repaint the background for every frame.

Computer animationComputer animation has advanced rapidly, and is now approaching the point where movies can be created with characters so lifelike as to be hard to distinguish from real actors.

Animation Techniques - Cel Animation

This image shows how two transparent cells, each with a different character drawn on them, and an opaque background are photographed together to form the composite image.

http://en.wikipedia.org/wiki/Traditional_animation

Example of a claymation Example of a computer animationhttp://en.wikipedia.org/wiki/Image:Pyramid_of_35_spheres_animation.gifhttp://www.dbprescott.com/girlanim.gif

Animation Techniques – Claymation And Computer Animation

Animation Layout Transition The simplest form of animation is

transition Transitions specify how the display

changes (such as fading to black) as a user moves from one item (such as slide or Web page) to another)

Examples : Spiral Stretch Zoom Checkerboard

Process / Information Transition Animation can be used to describe

complex information / process in an easier way Perform visual cues (e.g. how things work)

Basic Concepts Of Animation Input process

Digitize the drawings – to capture key frames containing the characteristic positions.

Post-processing may be required to filter glitches. Composition

Foreground and background figures combined Pan = take a portion of an image (e.g. just a person’s

face) Zoom = fill the entire screen with an image

In between process Movement from one position to another needs a

composition of frames with intermediate positions (intermediate frames) in between the key frames.

‘Inbetweening’ can be done using interpolation

Basic Concepts of Tweening

Consider the following sequence of key frames (key 13) of a bouncing ball:

1

2

3Keyframe 1 Keyframe 3

Keyframe 2

Basic Concepts of Tweening

Using linear interpolation to yield the in-betweening

1

2

3

Basic Concepts of Tweening

This is not realistic!

Looks like being deflected by some unknown source; it doesn’t match the rest; angle may be too sharp

Basic Concepts of Tweening

Better to use a spline (curved lines) formula

1

2

3

http://www.cadtutor.net/dd/bryce/anim/anim.html

Basic Concepts of Tweening

Basic Concepts

Changing Colors Computer animation uses color

lookup tables (CLUT) in a frame buffer and the process of double buffering.

Animation is done by manipulating the table.

E.g. cycle the LUT; this saves time and bandwidth.

Also called Palette Animation Palette Animations change only the

color palettes, while the images themselves remain the same.

The effect is very different.

http://images.beggerlybend.com/animpal/ap_flare2.gif

Other Animations

Other Animations Toggling on and off – For a “yes/no”

situation Rotating through several image frames –

just like still TV ads. Delta frame (frame created from preceding

keyframe based on those pixels that have changed) – very computationally intensive, requires storing of initial frame as bitmap.

Encoding of the changed pixel into RLE format.

Controlling Animation

Full Explicit Control Simplest of all. Just specify explicitly the change or

directly manipulate; e.g. for a linear presentation. Procedural Control

Based on communication between various objects to determine their properties.

In physically-based system, the position of one object may influence motion of another

In action-based systems, the individual actors may pass their positions to other actors to affect the other actor’s behavior.

Controlling Animation

Constraint-based Systems Some objects move in straight lines, others

don’t! Easier to specify with constraints than

explicit control. Tracking Live Action

Rotoscoping = specify the acting parts of the character and draw over it. (cartoon characters in real environments)

Controlling Animation

Use indicator to key points and use data glove to move the parts.

Kinematics and Dynamics (physics)Kinematics - relates to position and

velocity of points Dynamics – also follows the laws of

physics

Animations File Formats

Some file formats are designed specifically to contain animations :Macromedia Director (.dir and .dcr)Macromedia Flash (.fla and .swf)AnimatorPro (.fli and .flc)3D Studio max (.max)SuperCard (.pics)CompuServe GIF89a (.gif)

Applying Animation In Multimedia Systems

Applying Animation In MM Systems When do we need to use animation in a

multimedia system? Once we’ve established that, why not just

use video? These are some of the questions a

multimedia developer is typically faced with. Firstly, animation and video are very much

alike. Both are comprised of moving images and

both support sound and can depict motion or action.

Applying Animation In MM Systems One of the places where animation and

video do differ is the nature of the content itself.

Most of the time, animation uses vector graphics and flat colors for its content.

Video, on the other hand, often uses the equivalent of 24-bit color images to depict real people and real places.

Think of animation to be like a cartoon and video like a real movie with real actors and people.

Nevertheless, the line separating the two are becoming thinner with time.

Animation (like the famous stick man above), is often recognizable by its very nature to portray things and objects that are often not possible in the real world.

Video, is more likely to show real world events and people. We can usually tell the difference between video and animation right away.

Applying Animation In MM Systems

Applying Animation In MM Systems These days, however,

animation and video sometimes merge into a motion picture that is different from both pure animation and video, as we know it.

This allows the interaction between real people and cartoon characters. It is actually quite an achievement in film-making.

Applying Animation In MM Systems

So, where would it be suitable to use animation over video?

Consider a system which is trying to explain how a CD-ROM is read by the computer.

You have the option of either using text, images, audio (narration), animation or video to explain it.

All would work, but only one is best.

Applying Animation In MM Systems Text would be too long and confusing. Images would be better, but needs to

be complemented with a significant amount of text to be understood.

Audio can only explain what can also be read in words. Plus, if you missed something, it would be inconvenient to review.

Video is interesting, but how do we capture on video this particular process (CD-ROM being read) in reality and in a way that is easy to understand?

Applying Animation In MM Systems Finally, we are left with animation. Because of its nature to depict strange

and impossible things, we can illustrate how a CD-ROM works quite nicely.

The individual components can be taken apart and shown, in motion, how they all interact with one another.

Unfortunately, animation has its limitations.

Often, we are unable to find something specific in the form of a ready-made animation (which someone else has done) and have to create the thing ourselves.

Applying Animation In MM Systems

It requires effort and work, but the results are worth it.

Plus, we need not worry about copyright infringement, since we created it ourselves.

Nevertheless, the long arm of the law can still prosecute us if the content within the animation itself is owned by someone else.

So, if you create an animation you plan to use commercially (especially), make sure it is all yours from the ground up.

References

http://en.wikipedia.org/wiki/Animation http://www.cadtutor.net/dd/bryce/anim/a

nim.html