Upcoming Deadlines

Homework #9 – Stop-motion Character AnimationDue Wednesday, November 3rd (This Wednesday)10 points (5 points if late)

Homework #10 – Outline for Second Term PaperDue Wednesday, November 10th (Wednesday of next week)10 points (5 points if late)

Second Term Paper – Science Fact or Cinematic Fiction?Due Wednesday, November 17th 100 points (50 points if late)

For full schedule, visit course website:ArtPhysics123.pbworks.com

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Special Guest Animation JudgeThe top three stop-motion character animations (this Wednesday’s homework) will be picked by Jason Spencer Galsworthy of Dreamworks Animation (and formerly with Aardman Animation).

Homework Assignment #10

Outline of your Second Term Paper.Topic: Science Fact or Cinematic Fiction?

An important component of being a well-educated adult is the ability to distinguish between fact and fiction, between science and make-believe.

For this assignment, you will choose a single physics principle, such as conservation of energy or the action/reaction principle, and describe three scenes from three different films that incorrectly illustrate that physics law or principle.

Homework Assignment #10

For example, you can describe how the principle of action/reaction is violated during a fight sequence when one character recoils but without a matching reaction on the other character.

The three films you select can be animated or live-action featuring CGI animation special effects.

You are strongly encouraged to find three scenes that are as different as possible from each other yet have the same fundamental error in the physics.

Homework Assignment #10

Post your outline in a blog entry entitled, “Outline for the Second Term Paper.”

Outline due by 8am on Wednesday, Nov. 10th

10 points (if late, 5 points)

The term paper itself is due a week later. Length, structure, grading rubric, etc. are similar to

the first term paper.

Activating your Clicker* Turn on your clicker.* Enter the channel number or letter for

joining this class. Hit Enter/Send key.* Clicker should read AP123GF10* Type in your student ID; hit

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Survey Question

You attended the “Animation Show of Shows” last Friday evening.

True or False

Review Question

Synchronized standing and sitting by a stadium’s crowd is what type of wave?

a)Lateralb)Transversec) Longitudinald)Invitationale)Transvestical

AmplitudeWaveMotion

Transverse vs. Longitudinal Waves

Wave Motion

Amplitude

Amplitude

Wave Motion

Both types of waves can travel down a Slinky

http://www.youtube.com/watch?v=Rbuhdo0AZDU

b) Transverse

Review Question

When a buzzer is moving towards you the wavelength of the sound gets shorter.

The frequency of the sound is…

a) Higher b) Lower c) UnchangedShorter Wavelength

Doppler Effect

a)Higher

If moving towards you, wavelength shorter and frequency higher.

If moving away, wavelength longer and frequency lower.

Waves & SoundPart II

“Talkies”

The first feature film with synchronized sound, 1927’s The Jazz Singer, was made using Vitaphone, a sound-on-disc technology.

Sound-on-film, however, would soon become the standard for “talkies”by the early 1930s.

Sound-on-film sound track

Silly Symphonies

Silly Symphonies had many imitators, including Warner Bros.’s Looney Tunes and Merrie Melodies, as well as MGM's Happy Harmonies.

From 1929 to 1939, Disney studios created 75 cartoons in the Silly Symphonies series, starting with The Skeleton Dance.

This series dominated the Oscars, winning yearly from 1932 to 1937.

The Skeleton Dance (1929)

http://www.youtube.com/watch?v=jkhxjzc9uuE

South Park: Bigger, Longer & Uncut (1999)Disney (and the rest of the industry) believed that audiences would not sit through a feature-length animated feature with simplistic animation.

http://www.youtube.com/watch?v=6UMaTg3lSf4

South Park proved him wrong, making over $82 million worldwide, with a $21 million budget.Was it the catchy music?

Frequency & Pitch

The faster vibrations, have higher frequency. Higher frequencies results in higher pitch for the musical note.

Musical notes are sound waves of different frequencies.

Standing WavesWhen a wave

interferes with its reflection, this may create a standing wave.

Fundamental & OvertonesThe Fundamental is the lowest frequency standing wave.The Overtones are twice, three times, etc., the frequency of the Fundamental.

110 Hz (A2)

220 Hz (A3)

330 Hz (E4)

Frequencies of standing waves for a 6 foot long organ pipe

OctaveThe note produced by two strings, one half

the length of the other, sounded similar.In Western music these two notes are said to

be an octave apart.Higher note is twice the frequency of the

lower.

Sing “Some-where over the rainbow…”

Men and women typically sing an octave apart.

C5

C4

Perfect Fifth

If the second string is 2/3rd the length

then the two notes are said to be “a fifth apart.”

Higher note has 50% higher frequency.

G4

C4

Separation between tenor and bass or soprano and alto.

Sing “Twin-kle, twin-kle little star…”

Strings and PipesShorter the string or the pipe, the higher the frequency of the note that’s produced.

Brass InstrumentsResonant standing waves produced in a pipe (horn); the set of frequencies (notes) depends on the length of the pipe.

Valves used to vary the length through in pipe

Woodwind InstrumentsResonant standing waves also produced in a pipe but the pipe length varied by air holes (finger-holes, keys, or pads).

Flute

Clarinet

Saxophone

Oboe

Bassoon

Meter stick

Cor anglais

Demo: Playing a Straw

Can make a simple reed by cutting a straw, as shown, lightly placing it between your lips, and blowing hard.

What happens if you shorten the straw (e.g., cut it in half)?

Demo: Hoot TubesLarge tube has a metal screen near one

end.Heat screen with a flame.

Remove tube from the flame and it

plays like an organ pipe.

The sound created by the larger hoot tube has a larger:A) Frequency; B) Wavelength; C) Amplitude

Hoot Tubes, Analyzed

C) Amplitude.Remove the flame and hot

air rises from the screen, drawing in cold air.

Hot air rising through pipe causes vibration at natural frequency, which depends on the length of the pipe.

Amplitude depends on the diameter of the pipe.

FLAME

Natural FrequenciesMetal baseball bat

and wooden bat sound very different when dropped to the floor.

Different materials and shapes vibrate at their own natural frequencies.

Forced VibrationsVibrating guitar strings force the vibration

of the guitar’s body, producing the sound.

553 Hz 731 Hz

Circular rings indicate where the surface vibrates up and down

Demo: Tuning Fork & Sound Box

Tuning fork by itself is not very loud.

Sound is much louder if it is held against a sound box, such as the body of a guitar or any similar rigid surface.

The tuning fork forces the surface into oscillation at the same frequency.

ResonanceResonance occurs when forced vibrations match an

object’s natural frequency.

Oscillations grow in amplitude due to synchronized transfer of energy into the vibrating object.

Acoustic ResonanceIf the amplitude of the sound is sufficiently large, resonant vibrations can shatter a wine glass.

This may be achieved by exceptionally powerful singers (and by average singers using electronic amplifiers).

http://www.youtube.com/watch?v=BE827gwnnk4

Tacoma Narrows Bridge

In 1940, the first Tacoma Narrows bridge was destroyed by resonance.

First Bridge

Second Bridge

Wind-forced oscillations that happened to match one of the bridge’s natural frequencies.

Tacoma Narrows Bridge

First Bridge

Second Bridge

http://www.youtube.com/watch?v=j-zczJXSxnw

Wave SpectrumTo appreciate what it takes to create a realistic

animation of water, such as the ocean, it’s useful to understand the concept of wave spectrum.

Real CGI

The Abyss (1989)

James Cameron’s The Abyss won an Oscar for Best Visual Effects, thanks to ILM’s creation of the first CGI character made of water.

The Old Man and the Sea (1999)

Aleksandr Petrov, the paint-on-glass animator, creates a realistic ocean with a full spectrum of waves, from major surges to minor ripples.

http://www.youtube.com/watch?v=l2_KszEnlq0

Spectral Decomposition

A complicated wave pattern may be decomposed as a sum of simple waves.

The graph of intensity (or power) versus frequency is the spectral decomposition.

TimeAm

plit

ud

e

Decomposition into waves

Frequency

Inte

nsi

ty

Class Demo: Wave Spectrum

Timbre and SpectrumA musical instrument playing a single note

produces not just that note’s frequency but others as well, mostly overtones.

The frequencies produced by a flute playing an A (slightly flat) show that the fundamental (436 Hz) and the harmonic (872 Hz) have almost the same amplitude.

The spectrum of a tuning fork has (mostly) a single peak at the fundamental.

Why Instruments Differ

The unique spectrum of frequencies for a musical instrument gives that instrument a unique signature, which is called the instrument’s timbre (or quality).

Playing this note (196 Hz)

Ocean Wave Spectrum

High FrequencyShort Wavelength

Low FrequencyLong Wavelength

Inte

nsi

ty High Winds

LowWinds

As the wind speed increases, the intensity of the large surge waves increases dramatically while the short ripples increases much less.

“Timber” of a MaterialSpectrum of waves will be different for different materials due to density, viscosity, surface tension, depth of the fluid, etc.

Gushing Oil Well

http://www.youtube.com/watch?v=pDyqhOL1ePU

Jello waves

Media That Transmit Sound

Sound travels better through elastic liquids and solids, such as water and rocks, than through air.

This is due to the close proximity of the atoms as they vibrate. Sonar used by whale and dolphins

Demo: Wave Spectrum

Strike the iron grate and listen to the sound.

Next, loop the string loop on your finger and let the iron grate hang freely.

Place your fingertips in your ears.

Strike the iron grate again and listen to the difference in the sound.

Hear richer, louder sound transmitted by string

Demo: What Your Voice Sounds Like

Your voice sounds different to you when you hear it from a recording.

This is because when you are speaking aloud, most sound waves reach your ear traveling through the solid flesh and bone of your skull.

Leave yourselfa voice-mail

Oil on the Water

Wave spectrum changes due to oil slick

Exxon Valdez accident

Shallow Water Waves

As waves enter shallow water, they slow down, grow taller and change shape.

From www.seafriends.org.nz

Approaching Shore

As waves enter shallow water, they slow, grow taller and change shape. At a depth of half its wave length, the rounded waves start to rise and their crests become shorter while their troughs lengthen. Although their period (frequency) stays the same, the waves slow down and their overall wave length shortens. From www.seafriends.org.nz

Wave Bending

When wave fronts approach a gently sloping beach on an angle, they slow down in the shallows, causing them to bend towards the beach. If the beach slopes gently enough, all breakers will eventually line up parallel to the beach.

Beach

Surf ZoneThe waves steepen and finally break in the surf when depth becomes less than 1.3 times their height.

Waves change shape in depths depending on their wave length, but break in shallows relating to their height!

From www.seafriends.org.nz

Breakers

Spilling breakers are arise from long waves breaking on gently sloping beaches. There are several rows of breakers.

Plunging breakers can occur on moderate sloping beaches. There is only one row of breakers.

Surging breakers surge over steeply sloping (but not vertical) beaches or rocks. Waves break one at a time.

From www.seafriends.org.nz

Clash of the Titans (1981)

Notice how fake the waves looks because the spectrum and the timing are wrong.

Tidal wave scenes were created with scale models.

http://www.youtube.com/watch?v=JgiOx1fQzoA

Clash of the Titans (2009)

With modern CGI and a good understanding of physics it’s possible to make believable waves.

Nevertheless, you can have good physics and still make a bad movie.

http://http://www.youtube.com/watch?v=19jb4P8sYzw

Next LectureEffects Animation

Hot & ColdHomework 10 (Outline of 2nd Term Paper)

Due Wednesday, April 14th (This week)

Please return the clickers!