SWE 423 - 031- 61 Animation031)/6.1-Animation.pdfSWE 423 - MULTIMEDIA SYSTEMS Dr. Abdallah Al-Sukairi - KFUPM 2 Animation Animation is made from a series of stills and relies on something

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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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



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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.



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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

SWE 423 - 031- 61 Animation031)/6.1-Animation.pdfSWE 423 - MULTIMEDIA SYSTEMS Dr. Abdallah Al-Sukairi - KFUPM 2 Animation Animation is made from a series of stills and relies on something

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