Upcoming Classes

Tuesday, Sept. 11th

Motion and Dance, Part 1Assignment due:

* Read “Motions without Turns”, Physics and the Art of Dance, K. Laws, Pages 36-51

Thursday, Sept. 13th

Motion and Dance, Part 2

Assignment due:

* First draft of first oral presentation or written paper

Upcoming Deadlines

Thursday, September 13th

First draft of your first term paper or your

oral presentation

Thursday, September 27th

First Set of Oral Presentations

First term paper (if not giving presentation)

Oral Presentations

The following persons will give oral presentations on Thursday, September 27th :

• Batres, Adan• Boyd, Heidi• Chen, Emily• Kwiatkowski, Dajon• Lebedeff, Christopher• Lipton, ChristopherFor everyone else, your first term paper is due on

that date.

Extra Credit: SF Museum of Art

Visit San Francisco Museum of Modern Art and see Abstract Expressionist paintings.

Turn in your ticket receipt ($7 for students). Worth one homework assignment; deadline is Oct. 16th

Guardians of the Secret, Jackson Pollock, 1943

Quiz

Put your name on a sheet of paper and answer the following question from today’s reading assignment:

In animation, what is meant by the expression “slowing out”? Give an example of slowing out.

Pollock Extra Credit (1)

In the movie “Pollock” there’s a scene in which Jackson Pollock goes to a store and trades one of his paintings for something which he then brings home riding a bicycle.

What is it that Pollock gets from the store and what happens on his way home from the store?

Pollock Extra Credit (2)

In the movie “Who the F*ck is Jackson Pollock” the forensic detective investigating Teri Horton’s painting finds something interesting on the back of the painting, which leads him to visit Pollock’s original art studio.

What is it that he finds and why does he need to visit Pollock’s studio?

Motion in Real & Animated Worlds

Real World & Animated WorldUnderstanding the real world helps in creating interesting animated worlds.

"Animation follows the laws of physics — unless it is funnier otherwise.“Art Babbitt, Disney animator, director, and creator of Goofy

Motion & Mechanics

The study of motion is a fundamental field of physics known as mechanics.

“In order to do the fantastic we must first understand the real.” Walt Disney

Motion & Mechanics

Physical laws apply equally to living characters, living beings are just a little more complex (but then so is an automobile engine)

Thomas Eakins

Computer Generated Animation

Animation software, such as Maya, have sophisticated physics “engines” that use the laws of physics to compute motion.

The Four ‘A’s of Animation

In his book, Animation, The Mechanics of Motion, Chris Webster lists the following four levels for animated motion:

•Activity (arbitrary movement)•Action (physical motion)•Animation (purposeful motion)•Acting (motion with personality)

These categories are best understood by considering specific examples.

Activity (Level 1)

The opening sequence in the Star War’s movies is a good example of activity, the lowest level of animated motion.

The motion is arbitrary, without constraint of physical laws.

That moving ball was another example of activity.

Action (Level 2)

Action is the level of animation when objects move according to physical laws, such as a bouncing ball or a waving flag.

Animation (Level 3)

At this level the motion not only follows the physical laws but is also intentional, such as a bird flapping its wings or a human’s throw.

Acting (Level 4)

At this highest level not only is the motion intentional but it also conveys personality.

The Four ‘A’s of Animation (again)•Activity (arbitrary movement)•Action (physical motion)•Animation (purposeful motion)•Acting (motion with personality)

Physics is important in the first three levels and you cannot achieve acting without those first three levels.

Disney’s Principles of Animation

1. Squash & Stretch2. Timing3. Anticipation4. Staging5. Follow Through & Overlapping Action6. Straight Ahead & Pose-to-Pose Action7. Slow In and Slow Out8. Arcs9. Exaggeration10.Secondary Action11.Appeal

(from Disney Animation – The Illusion of Life, by Thomas and Johnston)

It’s all in the timing…

An essential element of animation is the timing between frames

“It’s not important what goes on each frame of film; it’s the spaces between the frames that are important. “ Norman McLaren

First Film: The Bouncing Ball

To learn basic timing, all animation students begin with the same film: the bouncing ball

Timing: Frames, Keys, & Clocks

We’ll use three different ways of measuring time:

• Frames (intervals of 1/24th of a second)• Keys (given number of frames between poses)• Clocks (actual seconds as measured by a clock)

IMPORTANT: We’ll select the keys such that there are always the same number of frames between each key.

Uniform Motion

1 2 3 4 5

EqualDistances

NOTE: In all examples there are an equal number of frames between keys

Rolling ball is an example of uniform motion.Velocity of the ball is constant (with no friction).

Arbitrary

Uniform Motion in Perspective

Uniform Motion in Perspective

Uniform motion may not appear uniform due to distortion of scale when shown in perspective.

Distance

s are equally

-

space

d, in persp

ective.

VanishingPoint

Horizon Line

Accelerating Motion & Falling

1

2

3

4

1

3

5

7

1

4

9

16

Falling is an example of accelerating motion (in animation, “slowing out”).

Distance between keys increases in the ratios 1:3:5:7:9… starting from point of release (key #1).

Total distance from point of release (key #1) increases in the ratios 1:4:9:16:25:… or 12:22:32:42:52…

In “Straight Ahead” animation after drawing keys #1 and #2 the positions of the rest are given by these rules.

Distance FallenTime (seconds)

Frames Distance fallen (key #1 to #2)

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

Distance fallen from key #1 (release point) to key #2 depends on the number of frames between keys.

Distance fallen from key #2 to #3 is three times further; from #3 to #4 is five times, from #4 to #5 is seven times, etc.

Note: These distance do not depend on the object’s weight.

Falling Bowling Ball

1 (Release)

2

3

3 frames per key(and dolly in)

4

6 frames per key

4

3

2

1 (Release)

Bowling ball is one foot in diameter.

Balls falls by one diameter in the first six frames.

Same times

5

5

(6 frames)

(12

fram

es)

Falls ¼ of diameter in the first three frames.

Demo: Catch a Buck

Put thumb and index fingers near Washington’s head. Can you react fast enough to catch the money?

Half length of dollar bill is 3 inch so it takes about 1/8 of a second (0.125 seconds) to fall this distance.

Typical reaction time is 0.20 to 0.25 seconds.

Measuring Reaction Time

Release

Catch

Distance (inches) Time (sec.)

1 0.072 0.103 0.124 0.145 0.166 0.177 0.198 0.2010 0.2312 0.2514 0.2716 0.2918 0.30

Rolling Downhill

13

7

1

2

3

4

Rolling downhill isalso accelerating motion

Very similar to falling except distances are smaller and depend on the slope of the incline.

Key #1 is point of release

5

Demo: Galileo’s Clicking Ramps

Roll balls down notched, inclined ramps and listen for the clicks.

Start

1 4 9 16 25 36 49 64

8 16 24 32 40 48 56 64

4=2x2 9=3x3 16=4x4 25=5x5 36=6x6 49=7x7 64=8x8

Sliding with Friction

Sliding this way

5 3 1

1 2 3 4

Sliding with friction is another example of accelerating motion but in this case the object “slows in.”

Draw last key (where object stops) first and draw keys leading up to it in the ratios 1:3:5:7:9:…

Blockstopshere

Speed Lines and Acceleration

1 2 3 4

Blockstopshere

With Friction

1 2 3

Without Friction

In accelerated motion, the velocity increases or decreases uniformly (e.g., velocity with friction could go from 6, to 4, to 2, and finally zero)

In uniform motion, the velocity remains constant (no acceleration)

Speed lines used to indicate velocity

Falling and Floating1

3

5

5

5

Accelerating Motion

Uniform Motion

Light objects, such as a beach ball, initially fall with accelerating motion.

Due to air resistance, the motion transitions to uniform motion after falling a certain distance.

For very light objects, such as a leaf, this transition is almost immediate.

5

Squirrels cannot die from a fall.

Hyper-acceleration

13

7

1

2

3

4

Constant accelerationRelease

5

1

2

3

4

Release

Hyper-acceleration

If the slope of an incline increases, the acceleration itself accelerates.

Tipping Over

A good example of hyper-acceleration is an object tipping over when off-balance.

Release

At 4º in ½ second

At 15º in

1 second At 5

7º in

1½

seco

nd

No simple way to compute hyper-acceleration.

Brick tipped 2º off-balance then released.

Acceleration “Stretch”

Objects do not physically stretch as they fall (not even raindrops).

Objects visually stretch as they gain speed due to motion blur.

Motion blur does not depend on the object’s material, however, it will look more natural for rigid objects to stretch less than elastic objects.

High-speed camera

Human eye

The Dover Boys

The Dover Boys is an animation classic by Chuck Jones (better known for Bugs Bunny, Daffy Duck, Road Runner, and others).

This cartoon has great examples of extreme “stretch”, also called “smear” animation.

Moving & Falling2 3 4

5

7

3

1Arbitrary 5

1

6

7

Ball rolling off of a table combines horizontal and vertical motion.

Falling starts with key #4, with vertical distances increasing as 1:3:5:7:…

Horizontal distances equally spaced as with uniform motion.

Arc is the combination of uniform horizontal motion and accelerating vertical motion.

Demo: Fall and Fire1

5

3

1 2

3

4 4

2

3

1FALL

FIRE

One ball is released and falls straight down.Other ball is fired horizontally.At all times the balls are at the same height.Hit the ground at the same time.

Parabolic Arc of Motion

2

3

4

5

7

3

15

1

6

7

Up and down motion is symmetric, as shown.Key #4 is highest point of the arc of motion.

ArbitraryApex

Bouncing with Squash & Stretch

Stretch is added where motion is the fastest.Squash is used to emphasize impact on bounce.

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

Add points to the curve by ‘tweening’ from the point of maximum height.

Maximum RangeMaximum range is at 45 degrees (when air resistance is negligible).

Demo: TrebuchetTrebuchet is a type of catapult popular in the 13th century.

ReleaseWarwolf45 degrees

Movie: Trebuchet

Contestant in annual pumpkin throwing contest, Punkin Chukin

Next Lecture Motion & Dance (I)

Remember:Read “Motions without Turns”, Physics

and the Art of Dance, K. Laws, Pages 36-51