Physics for Animation Artists

Alej Garcia* (Physics)Dave Chai (Art & Design)

San Jose State Univ.

Supported by the NSF/CCLI program*Presenting at AAPT Winter 2009 meeting, Chicago

AnimationThree basic types of animation:

Traditional Computer Stop-motion

As kids we knew these as “cartoons.”

Four of the top 10 grossing movies in 2008 were animated feature films (WALL-E, Kung-Fu Panda, Madagascar 2, and Horton Hears a Who!).

Animation-related WorkAnimation is also important in:

Video Games

Guitar Hero III sales topped $1 billion in the 2008 holiday season.

Top money movies of 2008 were Dark Knight, Iron Man, and Indiana Jones (each had over $300 million in domestic gross)

CGI for live-action films

Silicon Valley & SJSU

San Jose State is located in Silicon Valley at the south end of San Francisco Bay

Animation Program at SJSU

The Animation / Illustration program in San Jose State’s School of Art & Design has 5 permanent faculty, a dozen lecturers and over 400 majors.

Physics for AnimatorsTo create realistic animations, animators

need to understand principles of physics.

Anatomy for Artists

Surgeons and artists learn anatomy, but for very different purposes.Engineers and artists need different curricula in physics for their disciplines.

Leonardo da Vinci

Teaching Physics to Animators

For three semesters Dave Chai and I have been team teaching an upper-division animation class.

Prof. Dave Chai,Award-winning animator

Animation ExercisesAnimation is learned by exercises of

varying difficulty. The simplest is a bouncing ball; an intermediate exercise is a human jump.

PlayMovie

PlayMovie

Ball DropTime (sec)

Frames

Distance from apex

1/24 1 1/3 inch

1/12 2 1 1/3 inches

1/8 3 3 inches

1/6 4 5 1/3 inches

¼ 6 1 foot

1/3 8 1 ¾ feet

½ 12 4 feet

2/3 16 7 feet

¾ 18 9 feet

1 24 16 feet

The first exercise is the ball drop, which introduces constant acceleration.

We discuss the timing and spacing of the motion, such as in this example of a falling softball (4 inch diameter) animated “on twos.”

A Fourth Down at Half Time

3 frames per key(close-up)

6 frames per key(medium shot)

In time, Key #3 is half way between #1 and #5.

In space, Key #3 is a fourth of the way down between #1 and #5.This rule always applies for any key half-way in time from the point of release.

Timing a Jump

This jump looks to be about 12 inches in the air, which takes a total of 12 frames (6 from take-off to apex and 6 from apex to landing).

#1

#2 #3#4

#5Frame Key

1 #1

2 |

3 |

4 #2

5 |

6 |

7 #3

8 |

X

X XX

X

X = Center of Gravity

Timing the JumpFrame 78

Frame 82

Frame 87

The jump has 4 frames from take-off to apex and 5 frames from apex to landing.

The height of the jump, given the time in the air, should only be about 6-8 inches.

This jump looks to be about 12 inches high.

Play Movie

Path of Action

As with bouncing ball, the path of action is a parabolic arc.Apex needs to be above the half-way point between take-off and landing

Parabolic Arc in Perspective

VP

HL

Ball starts and ends on the ground.

Maximum height (ball at midpoint)

Parabolic Arc in Perspective (cont.)

VP

HL

1

3

Use “Fourth Down at Half Time” to fill in more points.

Apex of a Jump

Correct

Apex

Animation Physics Website

For more info, visit:

www.AnimationPhysics.com