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.

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

Oldest keyframe animationOldest keyframe animation

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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.

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

VideoVideo

중앙대학교 첨단영상대학원 박 경 주

Dynamics for Character AnimationDynamics for Character Animation

중앙대학교 첨단영상대학원 박 경 주

Rule-based BehaviorsRule based Behaviors

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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?

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

p

중앙대학교 첨단영상대학원 박 경 주

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

• Must not distract the audience

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주

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

중앙대학교 첨단영상대학원 박 경 주