Achieving believable motion in animation requires an understanding of physics that most of us missed out on in art school. Although animators often break the laws of physics for comedic or dramatic effect, you need to know which laws you¿re breaking in order to make it work. And while large studios might be able to spend a lot of time and money testing different approaches or hiring a physics consultant, smaller studios and independent animators have no such luxury. This book takes the mystery out of physics tasks like character motion, light and shadow placement, explosions, ocean movement, and outer space scenes, making it easy to apply realistic physics to your work.

• Physics concepts are explained in animator¿s terms, relating concepts specifically to animation movement and appearance.
• Complex mathematical concepts are broken down into clear steps you can follow to solve animation problems quickly and effectively.
• Bonus companion website at www.physicsforanimators.com offers additional resources, including examples in movies and games, links to resources, and tips on using physics in your work.

Uniting theory and practice, author Michele Bousquet teaches animators how to swiftly and efficiently create scientifically accurate scenes and fix problem spots, and how and when to break the laws of physics. Ideal for everything from classical 2D animation to advanced CG special effects, this book provides animators with solutions that are simple, quick, and powerful.

ACKNOWLEDGEMENT

FOREWORD

INTRODUCTION

SECTION I: CLASSICAL PHYSICS

CHAPTER 1: MATTER AND MASSES

Matter

Composition of Matter

Atoms and Binding

Nuclear Fusion

Masses

Mass vs. Weight

Center of Mass

CHAPTER 2: MOTION AND TIMING

Motion Lines and Paths

Linear Motion

Circular Motion

Types of Circular Motion

Rotational Motion

Rotation and Distance

Calculating the Number of Times a Wheel Turns

Spinning, Tumbling, and Wobbling

Centripetal Motion

When Centripetal Force Stops

Circular Speed

Centrifugal Force

Centripetal Force and Vehicles

Pendulum Motion

Wave Motion

What Waves Do

Visibility of Waves

Types of Waves

Transverse Waves

Longitudinal Waves

Wave Properties

Amplitude

Wavelength

Frequency

Wave Velocity

Wave Relations

Wave Phase

Wave Addition and Cancellation

Standing Waves

Common Sound Effects

Resonance

Doppler Effect

Sonic Boom

Timing

Timing Tools

Uniform Motion Timing

Slow In and Slow Out

Acceleration Timing

Constant Forces

Forces Exerted by Characters

Constant Force and Acceleration

The Odd Rule

Odd Rule Multipliers

Odd Rule Scenarios

Motion Graphs

Constant Speed

Acceleration

Acceleration of Gravity

Swinging

CHAPTER 3: FORCES

Components of Force

Familiar and Unfamiliar Forces

Familiar, Non-Random Forces

Unfamiliar Forces

Variable Forces

Gravity

Gravitational Acceleration

Common Misconceptions about Gravity

Timing for Gravity

Calculating Total Time and Distance

Physics-Based Calculations

Visual Calculation Methods

The Odd Rule

Fourth Down at Half Time

Falling a la Chai

Moving and Falling

Ascending Against Gravity

Projectile Velocity

Center of Gravity

Line of Gravity

Tipping and Center of Gravity

Lowering and Raising the CG

Friction

Static and Kinetic Friction

Friction on Flat Surfaces

Frictionless Surfaces

Coefficient of Friction

Effects of Friction

Pressure and Gases

Pressure Increase from Heat

Heated Gas in a Container

Heated Air in Atmosphere

Chemical Reaction

Force from Pressure Decrease

Atmospheric Pressure

Air Resistance

Aerodynamic Lift

Pressure Differences in Action

Torque

Torque Basics

Torque Terminology

Maximizing Torque

Visualizing Torque

Calculating Torque

Lever Systems

Efficiency vs. Speed

Neutral Efficiency

Lever System Classes

First Class Systems

Second Class Levers

Third Class Levers

Balancing Torque in a Lever System

Increasing Leverage

Torque in Animation

Rotational Inertia

Action / Reaction

Action/Reaction and Balanced Forces

Action/Reaction with Two Mobile Objects

Action/Reaction and Weight

Action/Reaction and Fixed Objects

Electricity and Magnetism

Electricity

Electrical Charge

Static Electricity

Flowing Electricity

Conductors vs. Insulators

Electric Current

Electric Shock

Sparks and Lightning

Magnetism

Magnetic Fields

Making a Magnet

Electromagnets

Demagnetization

Visualizing Electricity and Magnetism

Electric Shock

Electric Current

Magnetism

EMPs

CHAPTER 4: LIGHT AND COLOR

Light Basics

Light as Rays

Light and Reflection

Seeing in a Mirror

Bouncing Light Rays

Attenuation

Physically Based Lights

Shadows

Cast Shadows

Umbra and Penumbra

Sharp and Fuzzy Shadows

Shadow Angle

Light Source Shapes

Shadow Intensity

Form and Occlusion Shadows

Reflection

Specular Reflection

Diffuse Reflection

Diffuse Reflection and Light Intensity

Detecting Shape and Color

Diffuse vs. Specular Reflections

Diffuse Interreflection

Partial Reflections

Refraction

Caustics

Gamma Correction

Linear vs. Curved Light Intensity

Gamma Correction for Real World Perception

Gamma Correction and Cameras

Gamma Correction on Digital Files

Gamma Calculations

Monitor Gamma Adjustment

RGB Gamma Curves

Linear Workflow

Section II Character Design and Animation

CHAPTER 5: CHARACTER DESIGN

Size and Scale

Proportion and Scale

Weight and Strength

Physical Characteristics and Size

Posture

Deformability

Wing Size and Shape

Climate

Longevity

Sound

Babyness

Joints

Types of Joints

Animal Joints

Joints as Levers

Elbow

Foot

Neck

Muscles for Joints

Weight Distribution

Character Center of Gravity

Balance

Improving Balance

CHAPTER 6: CHARACTER ANIMATION

Jumping

Parts of a Jump

Calculating Jump Actions

Calculating Jump Timing

Jump Magnification

Jump Magnification and Acceleration

Push Time

Push Key Spacing

Motion Arc and Jump Timing

Landing

Stop Time

Very High Jumps

Walking

Poses

Strides and Steps

Walk Timing

Walking and Energy Efficiency

Horizontal CG Shift

Vertical CG Shift

Hip Rotation

Shoulder Rotation

Dancing and Gymnastics

Torque and Turning

Balance with Multiple Characters

Gymnastics Lever Systems

Lifting Weight

Shifting Body Weight

Sitting and Standing

Getting Hit

Fight Scenes

Momentum and Force of Impact

Changing Momentum

Force and Changing Momentum

Action/Reaction and Changing Momentum

Recoil

Tipping Over

Rotational Inertia and Tipping

Tipping and Friction

Drag and Follow Through

Drag

Follow Through

Overlapping Action

Length and Motion

Surface Area and Motion

SECTION III: VISUAL EFFECTS

CHAPTER 7: ENVIRONMENT

Clouds

What¿s in a Cloud

Types of Clouds

Cloud Altitudes

Inside a Cloud

Movement of Clouds

Cloud Effects

Cloud Combinations

God Rays

Backlit Clouds

Rain

Rain Formation

Types of Rain Clouds

More about Rain Clouds

Wind and Rain

Where Rain Forms

Predicting Rain

Weather from the West

Raindrops

Falling Raindrops

Invisible Raindrops: Puddle Effects

Slow-Moving Raindrops: Windowpane

Lightning

How Lightning Forms

Cloud-to-Cloud Lightning

Lightning Formation and Appearance

Effects from Lightning

Thunder

CHAPTER 8: FIRE AND EXPLOSIONS

Fire

Flames

Flame Appearance

Creating Flames

Smoldering Solid Matter

Fireball

Mushroom Clouds

Mushroom Clouds in Animation

Smoke

Smoke Appearance

Puffy Smoke

Tendril Smoke

Campfire Smoke

Explosions

Types of Explosions

Life of an Explosion

Before the Explosion

After the Explosion

Role of Containers

Timing for Explosions

Shockwaves

Shockwaves Through Air

Shockwaves Through the Ground

Breakage and Fracture

Anatomy of Fracture

Crack Patterns

Inherent Weak Points

Internal Cracks

Animating Breakage

How Physics Engines Determine Fracture

Flying Pieces

CHAPTER 9: FLUID EFFECTS

Properties of Liquids

Cohesion

Adhesion

Viscosity

Newtonian and Non-Newtonian Fluids

Solid/Liquid Behavior of Non-Newtonian Fluids

Surface Tension

Buoyancy

Liquid Appearance

Meniscus

Pouring Shapes

Oceans and Lakes

Waves

Wave Terminology

How Ocean Waves Form

Movement of Waves

Breaking Waves

Floating on a Wave

Ocean and Lake Appearance

Water Reflection

Color of the Ocean

Spray, Mist, and Foam

Shadows on Water

CHAPTER 10: EARTH AND OUTER SPACE

Earth Today

Earth¿s Layers

Atmosphere

Atmospheric Levels

Height of Vehicles in Atmosphere

Formation of Earth

Gaseous Earth

Supercontinents

Formation of Modern Landscape

Tectonic Shifts

Volcanism

Bombardment

Erosion

Glaciers

Earth¿s Crust

What¿s a Rock?

How Rock Forms

Rock Composition

Rock Classification

Causes of Geology

Geology from Magma

Geology from Compression

Geology from Heat and Pressure

Geology from Buoyancy

Geology from Weathering and Erosion

Designing a Landscape

Usual Rock Colors

Unusual Rock Colors

Life on Earth

Fossils

Meteorites and Life on Earth

Evolution and Diversity

Outer Space

Origin of the Universe

Stars

Galaxies

Properties of Galaxies

Nebulas

The Vacuum of Outer Space

Temperature in a Vacuum

Sound in a Vacuum

Radiation

Michele Bousquet is a longtime animator and instructor, and the author of more than 20 books on computer animation. Her freelance animation work has served clients like Autodesk and the Australian Broadcasting Corporation, and she has taught university-level animation classes at countless locations, including several art institutes. After years of answering questions about physics from animation students, Michele took on the task of formulating the answers into this book. Michele holds a Bachelor¿s degree in Mathematics and Computer Science from McGill University.