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SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Animation
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Animation
Representation of objects as they vary over time
Traditionally, based on individual drawing or photographing the frames in a sequence
Computer animation also results in a sequence of images, but these are created by software
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Animation
Animation is made from a series of stills and relies on something called persistence of vision
Persistence of vision is the phenomenon were an object on the eye’s retina remains for a brief time after viewing
This means that a series of still images which vary slightly, if shown rapidly will give the illusion of movement
If each of the eight pictures below were shown at the same point in rapid succession, the result would be a rotating arrow.
Animation
TV gives the illusion of continuous movement by showing the stills at the rate of 30 frames per second
Today, most animation is performed by computer. Examples are Bugs, Toy Story, and the BBCs Walking with Dinosaurs
The computer will produce a wire frame of the scene, then apply textures and light effects before moving onto the production of the next frame, each of which may take hours or even days to produce
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Why animate?
Animate means “to bring to life”
Because it is a good (and sometimes less expensive) way to show/say some things
The power of motion Visual effects
Wipes, fades, zoom, dissolveAnimated presentationsAnimated applicationsAnimated Web applications
ApplicationsAnimation has been used for entertainment, advertising, instruction, art and propaganda on film or video; it is also employed on the World Wide Web and in multimedia presentations
Microsoft DirectAnimation
A high-level DirectX APIs and controls that provides rich support for animation
Comprehensive support for different media types
A uniform time and event model that frees user from frame-level details
Can be used to build high-performance animation in a variety of environments
HTML, JavaScript, VBScript, Java, C++, VB
See DirectX Media SDK
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Animation Packages
Frame-based animationTweeningImage creation and image animation2-D image, 3-D imageAnimation files store a series of framesWireframe (mesh)Surface textureMorphingRendering
Web AnimationFlash from Macromediaplasma from Discreet
3-D Animation3ds max from Discreet (a division of AutoCAD)SOFTIMAGE|XSI from Softimage (a division of Avid Technology)Maya from Alias|Wavefront (a division of SGI)
What we are going to talk about?
Cel (and flipbook) animation
Sprite, path, vector animation
Key frames and tweening
Character animation
2D vs. 3D
… and other things
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Cel Animation
Cel Animation is the technique used to produce the old Tom & Jerry cartoons and the new computer generated Disney cartoons
It draws its name from the celluloid films used in old hand drawn animations
Moving elements in a scene are drawn on transparent materials known as cels (celluloid), now replaced by acetate or plastic
The celluloid films permitted layering, where the background to a sequence may be drawn on one or more films and then the films containing the animated characters place on top
Such animation starts with the production of keyframes, which are the first and last frames of an action scene
24 frames per second
Cel Animation
The frames in between the keyframes are then produced using a process known as tweening
Sketch onto a cel with pencilWhen the pencil frames are satisfactory, they are permanently inked
Tweening is where the number of frames which must appear between keyframes is calculated and the frames drawn
Tweening may be performed by computer if the frames are not too far apart
Only the moving elements on the cel need to be redrawn for each frame, the fixed part of the scene need only be made once
Animation cels are layered to produce a single animation frame
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Flipbook (Simple) Animation
Timer
Rotate through several pictures
Change location
Examplesflying butterflyflip bookbouncing ball
problem: takes too much time (especially over the Internet)
compression techniques are usually proprietary (different type of images!)
Palette Animation
Simulate motion by color cyclingrapidly changing the colors of selected entries in a color palette or switching between multiple palettese.g. running waterquick method of creating animation that requires very little memory
GDI functionsSelectPaletteSelectPaletteEntriesRealizePaletteCreatePaletteAnimatePalette
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Sprites and Paths
Sprite: a part of the animation which moves independently of the rest
Anything can be a sprite: ball, animal, human, …
A sprite can be attached to a path (or vice versa), so that successive sprite positions are located on a path
Sprite can animate in-place, or move along a path, or both
Splines and Vectors
Paths can be linear
More often, paths follow a spline curve
Sprites can be describedas raster objects
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Key Frames
Most important frames are drawn first:key frames
establish the main dramatic poses,define the flow of actions, and create the overall graphic style of the animation
Tweening
Tweening: frames are inserted between the key frames
Computer can do much of the tedious work
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Motion Interpolation
Motion along an arbitrary line
Computer performs the interpolation
Special effects (rotation, resizing) can be specified along the line
Morphing
Transformation of one image into another
A number of key points is set on both images
Actual transformation is calculated on the basis of transformation (in both position and color) of key points
More key points + more intermediate steps = smoother transformation
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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2D vs. 3D
Our perception of the world is three-dimensional
3D effects improve visual appearance
3D special effects can be added to 2D images (most drawing/painting programs can do it)
3D images can be generated from appropriate scene setups
… but: sophisticated applications are required
Kinematics
Considers only motion
Determined by positions, velocities, accelerations
Forward kinematicsLow level approach where animator has to explicitly specify all motions of every part of the animated structureEach node in hierarchy inherits movement of all nodes above it
Inverse kinematicsRequires only the position of the ends of the structureFunctions as black box - controls detailed movement of entire structure
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Forward Kinematics
Animator specifies joint angles
Computer finds position of end-effector: X
Inverse Kinematics
Animator specifies end-effector positions
Computer finds joint angles
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Kinematics Summary
Forward KinematicsAnimator has complete freedom over the movements of any part of the structureAmount of work is function of the complexity of the structure, much more expensive when dealing with complex structures
Inverse KinematicsDoes not leave much scope for the animator to inject ‘character’ into the movementsModel does not possess the interpretation of a human beingOverall movement of structure depends on the formula same footprints, same movements
Character Animation
Often the trickiest part – many simultaneous movements involved
Faces are very difficult to animate
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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3D effects
Adding depth to 2D images
Effects likeextrudingshadowshighlightsembossingtexturingspecial lighting effects
Step 1: Creating Storyboards
detailed storyboard drawings are created as the blueprint for the action and dialog
there can be as many as 3 to 4 thousand such drawings for a feature-length movie (which comes to about onedrawing everytwo seconds or so)
they are revisedmany times duringthe creativedevelopment process
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Step 2: Modeling
specialized animation software is used to create three-dimensional computer models of characters, props, and sets
computer models describe the shape of the object as well as themotion controls thatthe animators use tocreate movementand expressions
Step 3: Animation
specialized animation software allows animators to orchestrate the motion in each scene by defining key frames or poses
computer automatically creates the "in-between" frames
animators neitherdraw, nor paint thescenes, as is requiredin traditionalanimation process
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Step 4:
surface characteristics, including textures, finishes and colors, are added to every object in the scene
textures can simulate a wide variety of appearances
textures may be 2Dimages or proceduralalgorithms
additional properties:reflectivity,transparency …
Step 5:
Using "digital lights," every scene is lit in much the same manner as stage lighting
Key, fill and bounce lights and room ambience are all defined and used to enhance the mood and emotion of each scene
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Lighting is the key
Key light – the brightest
Fill light – opposite the key light, reduces contrast and shadows
Back light – reduces shadows, separates the subject from the background
Step 6: Rendering
rendering software (Pixar's proprietary RenderMan) "draws" the finished image by computing every pixel of the image from the model, animation, shading, and lighting information
once rendered, finalimages aretransferred to film,video, or CD-ROM
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Stages of 3D Animation
3D modeling
Motion specification
Motion simulation
Shading, lighting, rendering
Postprocessing
Motion Generation
KeyframingAllows fine control but does not ensure the naturalness of results
Procedural Methods and Motion CaptureRealistic motion, however allows little control over fine details
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Procedural Methods
Computer procedurally follows the steps in an algorithm to generate motion
SimulationsPassive systems
No internal energy source, moves only when an external force acts on them
Active systemsInternal source of energy, can move of their own volition
Easy to generate a family of similar motions Particle systemsFlexible surfaces
Motion Capture
capture of motion of (human) actorwhole body, upper body, face
Technology – optical, magnetic, mechanical
Employs special sensors (trackers) to record motion of human performer
ProblemsDifficult to accurately measure motion of human body – clothes may shift, etcIf object used to generate recorded motion and graphical object have different dimensions -> animation will have noticeable flaws.
SWE 423 - MULTIMEDIA SYSTEMS
Dr. Abdallah Al-Sukairi - KFUPM
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Virtual Reality
Head-mounted displays
Data gloves track hand movements
Haptic interfaces provide tactile feedbackHaptics is the study of human touch and interaction with the external environment via touch 'Haptic' comes from a Greek term meaning 'able to lay hold of'
For flight and industrial simulation, games
Animation
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6.2 Web Animation