introduction.ppt [호환 모드]cau.ac.kr/~kjpark/courses/2008_2_ca/introduction.pdfaims • thi i d...

AimsAims

Thi i d i d t b th th th• This course is designed to cover both the theory and practice of the 3D computer graphics t h i f i t i ti dtechniques focusing on computer animation and simulation.

• In the lab sessions, students are exposed to pvarious modeling representations and rendering techniques, and they are expected to complete a q y p pproject using various modeling and rendering software (e.g., Maya).

중앙대학교 첨단영상대학원 박 경 주

( g y )

TopicsTopics

L t th t i• Lectures cover the topics on – Interpolation– Curves– Hierarchical kinematic modeling– Hierarchical kinematic modeling– Rigid-body simulation

M d li l h– Modeling natural phenomena– Modeling and animating articulated figures.


IntroductionIntroduction

Wh t i A i ti ?• What is Animation?– Making Things Move

– Series of pictures of objects/characters in motion

• Topics– Keyframe Animation– Physics Based Animation– Character Animation


TextsTexts• 1st 4th wk• 1st – 4th wk

– Computer Animation: Algorithms and Techniques by Rick Parent– 3D Computer Graphics by Alan Watt

• 5th – 10th wk– Siggraph course notes "Physically Based

Modeling“ (http://www cs cmu edu/~baraff/sigcourse/index html)Modeling (http://www.cs.cmu.edu/~baraff/sigcourse/index.html)• 11th ~ wk

– Computer Animation: Algorithms and Techniques by Rick Parentp g q y• Programming Help

– Numerical Recipes in C (http://www.numerical-recipes com/index html)recipes.com/index.html)

– OpenGL Programming Guide


Oldest keyframe animationOldest keyframe animation

19th t 의 i i• 19th century 의 moving images– 10 frames/sec– 각각의 영상 사이에 blackness


2D animation2D animation

숙련된 애니메이터• 숙련된 애니메이터

– Keyframes 을 그림

• 덜 숙련된 애니메이터

In between frame 을 그림– In-between frame 을 그림

• 많은 시간 소요

• 실제와 비슷한 애니메이션 제작 어려움


Story Boarding (Bug’s Life)Story Boarding (Bug s Life)• http://www pixar com/featurefilms/abl/behind pop4 html• http://www.pixar.com/featurefilms/abl/behind_pop4.html


Expressive AnimationExpressive Animation

Th f h lf fill d• The famous half-filled flour sack, guide to maintaining volume in any animatable shape, a y a atab e s ape,and proof that attitudes can beattitudes can be achieved with the i l t f hsimplest of shapes.


Computer-assisted AnimationComputer assisted Animation

• Toy Story중앙대학교 첨단영상대학원 박 경 주

y yhttp://www.pixar.com/shorts/

3D animation3D animation

A i t• Animator– 3D 로 중요한 keyframe 을 명시

• Computerin between frame 을 생성– in-between frame 을 생성

– 역학(dynamics) 기반의 motion 생성

• Still 많은 시간 소요Still 많은 시간 소요

• Pixar : 4 yrs to produce Toy Story


Motion CaptureMotion Capture

R d f li ti• Record from live action– Track motion of reference

pointspoints• Body or face or hands

Convert to joint angles– Convert to joint angles– These angles to drivean articulated 3 D modelan articulated 3-D model– These motion paths can be adapted andcan be adapted and generalized


DynamicsDynamics

G t ti b if i d f• Generate motion by specifying mass and force, apply physical laws (e.g. Newton’s Laws)

• Simulates physical phenomena– Gravity– Momentum (inertia)– Collisions– Friction– Fluid flow(drag, turbulence, …)– Solidity, flexibility, elasticity– Fracture


Physics for Natural PhenomenaPhysics for Natural Phenomena

A t t i l ti l t d t h i• Antz water simulation, related techniques were used in Shrek


VideoVideo


Dynamics for Character AnimationDynamics for Character Animation


Rule-based BehaviorsRule based Behaviors

R l 1• Rule 1• Rule 2• Rule 3• Rule 4• Rule 5Rule 5• Rule 6


Principles of AnimationPrinciples of Animation• From Disney Animation: The Illusion of Life by• From Disney Animation: The Illusion of Life by

Thomas Johnson, Ollie Johnson

• Open question: how to support these principles in computer tools?in computer tools?

J h L t P i i l f t diti l i ti• John Lasseter. Principles of traditional animation applied to 3D computer animation. Proceedings of SIGGRAPH(Computer Graphics)Proceedings of SIGGRAPH(Computer Graphics) 21(4):35-44, July 1987


Principles of AnimationPrinciples of Animation• Squash and stretch• Squash and stretch• Staging• TimingTiming• Anticipation• Follow throughFollow through• Overlapping action• Straight-ahead vs. pose-to-pose vs. blockingg p p g• Arcs• Slow in, slow out• Exaggeration• Appeal


The flour sackThe flour sack• Characters composed of• Characters composed of

living flesh do not move rigidly

• Preservation of volume is key

• Disney animators demonstrate with a half filled bag of flourbag of flour

Do we have computer-createdDo we have computer created animation that is as expressive as this?


Squash and stretchSquash and stretchSquash: flatten an object or character by pressure or by itsSquash: flatten an object or character by pressure or by its

own powerStretch: used to increase the sense of speed andStretch: used to increase the sense of speed and

emphasize the squash by contrast

Note: keep volume constant!

Weight is given using timing

Add squash/stretch to define the motion and show the speed


p

Anticipation and StagingAnticipation and Staging

Tell the audience• Tell the audience what you are doing b f d itbefore you do it

• Present the idea so it is unmistakably clear. Audience can only ysee one thing at a time. Useful guide: gstage actions in silhouette


Straight Ahead and Pose to poseStraight Ahead and Pose to poseScene drawings 에사용되는두가지방법

• Straight Ahead ActionSt t / id

• Pose to PoseD th k f

g

– Start w/ an idea– Draw all frames until

done

– Draw the key frames firstFill in the in betweensdone

– Good for frantic motion such as a character

– Fill in the in-betweens

such as a character jumping around in excitement


Follow Through and Overlapping ActionFollow Through and Overlapping Action

E thi h ld t• Everything should not have to stop at once

h iwhen a pose is reached

• The way the action is ycompleted

=> tell about a tell about a character


Slow in and Slow outSlow in and Slow out

A i t ifi th i k• Animator specifies the primary or key frames which are most important

• In order to stress these frames, move slowly away from one key frame quickly inslowly away from one key frame, quickly in the in between frames, and slowly into the ne t framenext frame

• Most time is spent on/near the key framesp y


ArcsArcs

M ti i t i ht li i t i• Motion in straight lines is not organic• Most human motion happens on curved pp

trajectories or arcs


TimingTiming

Th b f d i d t i th• The number of drawings determine the amount of time it takes on the screen– No inbetweens: character hit with a huge

force and his head is nearly snapped offy pp– Two : nervous tic, muscle spasm

Five : Come on hurry– Five : Come on… hurry– Seven: tries to get a better look at something– Ten: stretches a sore neck


ExaggerationExaggeration

W lt Di t d ti ith• Walt Disney wanted exaggeration with believability

• To him, realism meant “convincing” like real people arereal people are

• If the character was sad, make him sadder, if he was tired, make him more tired


Secondary ActionSecondary ActionAction aside from that of the primary character• Action aside from that of the primary character

• Must not distract the audience


Solid Drawing and AppealSolid Drawing and Appeal

A i t t k h t d b f• Animators must know how to draw before they can animate

• Appeal is what makes people want to look at a characterat a character


Affine GeometryAffine Geometry

V t S• Vector SpaceP(x1,y1) Q(x2, y2)

– Distance of two points– Distance of two points – Direction & Magnitude

• Affine SpaceAffine Space– Vector Space & Points & Operations


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