Multimedia object types: animation ISMT multimedia Dr Vojislav B Mišić.

Multimedia object types:animation

ISMT multimedia

Dr Vojislav B Mišić

Animation Technically, similar to video – a sequence

of still images Images created artificially, as opposed to

video (which presents something happening in the real world, maybe retouched)

Why? Because it is a good (and sometimes less expensive) way to show/say some things

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

Flipbook animation displaying a sequence of graphic files

(e.g., a slide show) problem: takes too much time (especially

over the Internet) solution: some form of compression (we

will discuss this in more detail later) compression techniques are usually

proprietary (different type of images!)

Cel animation animation created by a sequence of still

images (as always) different characters, objects, backgrounds

overlaid to obtain the final image final image is shot frame by frame changes are made only to objects which

move multiplan camera (Disney): distance

between layers in order to create an illusion of depth

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, but

that is unrealistic more often, paths follow

a spline curve watch for gravity! example: mixed feelings sprites can be described

as raster objects

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 areinsertedbetweenthe key frames

computer can do much of the tedious work

Motion interpolation Motion along an arbitrary line Computer performs the interpolation Special effects (rotation, resizing)

can be specified along the line

Character animation often the trickiest part – many

simultaneous movements involved faces are very difficult to animate sometimes

cutouts areused forbody parts

Other design effects ease-in and ease-out velocity curves line-of-action secondary action and overlapping

action follow-through hierarchical motion exaggeration

Anticipation, action, reaction Action/reaction is often anticipated before it

actually happens Sometimes aided by showing small

movements immediately before the action Reaction-recovery: small movements in the

opposite direction immediately after the action

Fake: the action itself is not shown, only what happens before and immediately after

Kinematics (in mechanical engineering) study of

motion of rigid objects and structures (in motion picture technology) study of

motion of (rigid) objects and structures with joints

examples: men (objects) walking, running,falling down or apart

inverse kinematics: calculating the motion form predefined key positions, under the given set of constraints

Morphing transformation of one image into another very popular a few years ago 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

Some rules to be obeyed …

Animated GIFs a sequence of still images (actually

GIF images according to GIF89a standard), packed for the Internet

suitable for simple animations small size = short loading time several tools available (including one

from Microsoft)

Macromedia Flash Quickly becoming de facto standard Compact export format, players Ability to incorporate raster images

as well as vector objects Powerful 2D motion effects Hotspots to support interactivity More on Flash in the lab sessions …

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

3D effects adding depth to 2D images effects like

extruding shadows highlights embossing texturing special lighting effects

Genuine 3D genuine 3D worlds rendered into 2D

images tasks in creating 3D: a brief

overview according to Pixar

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

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 choreograph 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

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

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

Powder your nose

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

Summary

Animation is often the simplest way to accomplish motion

If you want to go beyond what Flash can offer, be ready for surprises …