Computer Graphics LET US ENTER INTO THE MAGICAL

Computer Graphics

LET US ENTER INTO THE MAGICAL WORLD OF ANIMATION

Contents • • INTRODUCTION APPLICATIONS DESIGN OF ANIMATION SEQUENCES GENERAL COMPUTER ANIMATION FUNCTIONS RASTER ANIMATIONS COMPUTER ANIMATION LANGUAGES KEY FRAME SYSTEMS MOTION SPECIFICATIONS

Computer Animation What is Animation? Make objects change over time according to scripted actions What is Simulation? Predict how objects change over time according to physical laws 4

Introduction • Computer animation is the process used for generating animated images (moving images) using computer graphics. • Animators are artists who specialize in the creation of animation. • From Latin animātiō, "the act of bringing to life"; from animō ("to animate" or "give life to") and -ātiō ("the act of"). 2 D ANIMATION 3 D ANIMATION

APPLICATIONS Video games cartoon Mobile phones

Design Of Animation Sequences • Steps for designing animation sequences. 1. Storyboard Layout 2. Object definitions 3. Key frame specifications 4. Generation of in-between frames

Storyboard Layout

Object Definitions

Key frame Specifications

In-between frames

GENERAL COMPUTER ANIMATION FUNCTIONS • Animation software provide basic functions to create animation and process the individual object. Manipulate data object database. FUNCTIONS Motion generation. Object rendering. Amorphium Art of illusion

Raster Animations Real-time animations can be generated using raster operations.

ORGANISATION OF A VIDEO COLOUR TABLE 0 1 0 0 0 1 41 H 65 255 24 -bit 65 0 0 0 1 0 0 0 0 Pixel value 0 Red Green Blue Monitor

Computer Animation Languages • GENERAL PURPOSE LANGUAGES: • C, C++, Pascal, or Lisp(control animation sequences).

SPECIALIZED ANIMATION LANGUAGES • Key frame systems • Parameterized systems • Scripting systems

Key frame Systems

Motion Specifications • Various ways in which motions of objects ca be specified as: • Direct Motion Specification. • Goal-Directed Systems. • Kinematics and Dynamics.

Direct Motion Specification

Goal Directed System

Kinematics and Dynamics • KINEMATICS: • Motion parameters such as position , velocity and acceleration are specified without reference to the forces. • INVERSE KINEMATICS: • Initial and final positions of objects at specified times and from that motion parameters. • DYNAMICS: • The forces that produce the velocities and accelerations are specified(physically based modeling). • It uses laws such as Newton’s laws of motion , Euler or Navier -stokes equations.

Outline Principles of Animation Keyframe Animation Articulated Figures 23

Principle of Traditional Animation • • • Squash and Stretch Slow In and Out Anticipation Exaggeration Follow Through and Overlapping Action Timing Staging Straight Ahead Action and Pose-to-Pose Action Arcs Secondary Action Appeal 24

Squash and Stretch Squash 25

Slow In and Out 26

Anticipation 27

Computer Animation Pipeline • • • 3 D modeling Motion specification Motion simulation Shading, lighting, & rendering Postprocessing 28

Outline Principles of Animation Keyframe Animation Articulated Figures 29

Keyframe Animation Define Character Poses at Specific Time Steps Called “Keyframes” 30

Keyframe Animation Interpolate Variables Describing Keyframes to Determine Poses for Character in between 31

Inbetweening Linear Interpolation • Usually not enough continuity 32

Inbetweening Spline Interpolation Maybe good enough 33

Inbetweening Spline Interpolation • Maybe good enough • May not follow physical laws 34

Inbetweening Spline Interpolation • Maybe good enough • May not follow physical laws 35

Inbetweening Inverse Kinematics or Dynamics 36

Outline Principles of Animation Keyframe Animation Articulated Figures 37

Articulated Figures Character Poses Described by Set of Rigid Bodies Connected by “Joints” Base Arm Hand Scene Graph 38

Articulated Figures Well-Suited for Humanoid Characters 39

Articulated Figures Joints Provide Handles for Moving Articulated Figure 40

Inbetweening Compute Joint Angles between Keyframes consider the length constancy Right 41 Wrong

Example: Walk Cycle Articulated Figure: Hip Upper Leg (Hip Rotate) Upper Leg Hip Rotate Knee Lower Leg Ankle Foot 42 Lower Leg (Knee Rotate) Hip Rotate + Knee Rotate Foot (Ankle Rotate)

Example: Walk Cycle Hip Joint Orientation: 43

Example: Walk Cycle Knee Joint Orientation: 44

Example: Walk Cycle Ankle Joint Orientation: 45

Challenge of Animation Temporal Aliasing • Motion blur 46

Temporal Ailasing Artifacts due to Limited Temporal Resolution • Strobing • Flickering 47

Temporal Ailasing Artifacts due to Limited Temporal Resolution Strobing • Flickering • 48

Temporal Ailasing Artifacts due to Limited Temporal Resolution • Strobing • Flickering 49

Temporal Ailasing Artifacts due to Limited Temporal Resolution • Strobing • Flickering 50

Motion Blur Composite Weighted Images of Adjacent Frames • Remove parts of signal under-sampled in time 51

Space Time Constraints Editing Motion Original 52 Adapted

Space Time Constraints Morphing Motion The female character morphs into a smaller character during her spine 53

Space Time Constraints Advantages Free animator from having to specify details of physically realistic motion with spline curves Easy to vary motions due to new parameters and/or new constraints Challenges Specifying constraints and objective functions Avoiding local minima during optimization 54

Dynamics Other Physical Simulations Rigid bodies Soft bodies Cloth Liquids Gases etc. Cloth Hot Gases cgvr. korea. ac. kr 55