Upcoming Deadlines

Homework #11 – Building a Scene in MayaDue Tuesday, November 22nd (Only class meeting next week)20 points (10 points if late)

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

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Homework #11For this assignment you will create a simple scene; the assignment that follows will be to light the scene in a variety of ways.

In both of these assignments you will be using Autodesk Maya, a popular software application used in animation.

You can download a 30-day trial version of Maya from the Autodesk website.

Homework #11The scene that you create in this assignment consists of a floor, a single wall in the background, and some objects in the foreground.

Those objects need to be arranged so that they create the shape of the initials of your name.

Position the two letters so that they rest on the floor or on each other; do not have themtouching the vertical wall.

Homework #11

This simple scene was created by Candice Downey.

Homework #11Alternative non-Maya Assignment: If you are unable to use Maya then create a scene like the one described above using real objects (blocks, books, etc.) and photograph the scene. In next week's assignment you will light this scene in a variety of ways so be sure that you can recreate it for that assignment.

This assignment is due by 8am on Tuesday, November 22nd

20 points (if late, 10 points)

Survey QuestionHow did your stop-motion character

animation turn out?A) Very goodB) GoodC) FairD) PoorE) Didn’t complete it

Review QuestionThe longer strings of a harp and the longer pipes of an organ produce sounds with:

A) Higher frequenciesB) Lower frequenciesC) Equal frequencies

Wavelength and FrequencyB) Lower frequenciesLonger strings and pipes produce sounds with

longer wavelengths and thus lower frequencies.

For example, if the length is doubled then the frequency is halved, lowering the note by one octave. Men and women

typically sing an octave apart.

C5C4

High note

Low note

Review QuestionWhen the forced vibrations match an object’s natural

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

This is called:A) SpectrumB) Acoustic BeatC) SurgingD) ResonanceE) Harmony

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

http://www.youtube.com/watch?v=Pq-PxdOarjA

Review QuestionA musical instrument playing a single note produces

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

The unique “signature” of an instrument’s spectrum is called:

A) HarmonyB) MelodyC) TimbreD) RhythmE) Symphony

Why Instruments DifferC) Timbre

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)

“Timbre” 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

Optics & LightingPart I: Ray Tracing

LightingLighting is important in all the visual arts, from painting to cinematography.

The Orrery, Joseph Wright (1766) Humphrey Bogart in The Maltese Falcon (1941)

Up (2009)Let’s look at how lighting in used in a a scene from Pixar’s Up.

Key Lighting (One-Point)Simplest type of lighting is with a single dominant light source, called the key.

Traditionally, this light source is located on the left side of the scene.

Utah TeapotThe Utah teapot or Newell teapot is a 3D computer model which has become a standard reference object (and an in-joke) in the computer graphics community. It is a mathematical model of an ordinary teapot of fairly simple shape, which appears solid, cylindrical and partially convex.

The teapot model was created in 1975 by early computer graphics researcher Martin Newell at the University of Utah.

Cast Shadows & Form Shadows

Form ShadowCast Shadow

Cast ShadowsSize and sharpness of a cast shadow depends on:• Size of the light source• Distance from light to object• Distance from light to wall

Cast Shadow for Directional Light

UMBRAObject

Wal

l

A directional light has parallel light rays so the cast shadow is simple to trace on the wall.Dark shadow called the umbra.

Shadow is sharp (not fuzzy).

Creating Directional LightLight sources, such as bulbs, send light in all directions; directional lighting is created with mirrors or lenses to form the light into a beam.

“Barn doors”

Cast Shadow for Point Light Source

UMBRA

Light source(Point) Object

Wal

lShadow is sharp (not fuzzy).

Size of shadow depends on:* Distance from the light to object* Distance from object to wall

Light rays spread out from a point light source, such as a bright light bulb or a candle.

Film Noir Shadows

Shadow Of A Doubt (1943)

M (1931)

Film noir makes extensive use of cast shadows, manipulating their size for dramatic effect.

I Confess (1953)

Cast Shadow for Area Lights

UMBRA

Penumbra

PenumbraLight source

Object

Wal

l

Rays from a large light source to wall to map out location of deep shadow (umbra) and fuzzy shadow (penumbra).

The larger the light source, the smaller the umbra.

Umbra and PenumbraAn ant on the ground standing in the penumbra could see part of the sun.

Standing in the umbra part of the shadow, the ant wouldn’t see the sun at all.

No Shadow

Penumbra

Umbra

Solar Shadows

UMBRAPenumbra

Sun

Object

The width of the penumbra for a shadow cast by the Sun equals about 1% of the distance from the object to its shadow.

Floor

Angle = ½ degree

()

Distance

Diagram is not to scale

LIGHT

Example: If an object is 9 feet (108 inches) from the ground, the penumbra is a little more than 1 inch wide.

Penumbra SizeNotice how the size of the shadows’ penumbra increases as the shadow gets farther from the base of the tree.

Very far from the base the penumbras on each side meet and there’s no more umbra.

Solar Eclipse Seen from Space

…. And another

Light Intensity & DistanceThe intensity of light decreases as we get farther from the light source.

For a point light the intensity decreases quadratically, that is, at twice the distance you have a four times less intensity.

The light gets weaker because it is spread over a larger area.

Demo: Perspective CardsHold large card at

arm’s length.Close one eye then

hold small card at a distance such that it is same size as large card.

That distance will be half way between your eye and large card.

1

1 2

3 4

Arm’s lengthHalf

Area & Distance

These four figures are equally spaced indistance and, in perspective,you are standing that distance from the first.

At twice the distance,the face is ¼ the size.

At four times the distance face is 16th the size.

Light Intensity & AngleAs angle between the light and a surface increases, the intensity of the light on the surface decreases because it is spread over a larger area.

7 light rays hit surface

5 light rays hit surface

Seasons of the YearNorthern Hemisphere is warm in July because Earth is tilted towards the Sun.Southern Hemisphere is cold in July since it’s tilted way from the Sun.

The seasons are reversed in January.

Equator

Lighting and Dimension

Intensity of light striking a surface varies with angle so the gradient created by a key light is a strong visual cue of an object’s curvature and shape.

Form Shadow for Point Light Source

Light source(Point)

Object

The form shadow is completely dark if point source is the only light source (i.e., no ambient or reflected light).

Object is brightest where the rays hit head-on and dims going up to the terminator.

Terminator

Form Shadow for Area Light Source

Light source(Area)

A B C

View from A View from B View from C

Terminator widens into a penumbra for an area light.

Ambient Light

Direct

Direct

DirectAmbient Ambient

Ambient

Most lighting is indirect, coming not from a light source but from reflections off of other surfaces.

Fill Lighting

Key

Fill

Key+Fill

With two-point lighting the fill light softens the contrast by adding ambient light.

Rim Lighting

Key+Fill

Rim

Key+Fill+Rim

Adding a rim light shining from behind distinguishes the foreground objects from the dark background.

Three-point Lighting

Rim

Key+Fill+Rim

Three-point lighting (Key, Fill, and Rim) is a formula that Hollywood has used for years.

From Casablanca (1942)

Three-point lighting usually looks good but sometimes too good, that is, it seems fake.

Inconsistent Shadows

The Birth of the VirginFra Carnevale, 1467

The perspective in this painting is pretty good but what’s wrong with the shadows?

Inconsistent Shadows

The Birth of the VirginFra Carnevale, 1467

Long shadowsfrom left to right

No shadows?

Rising shadows?

Downward shadow?

Variety of errors yet not immediately noticeable.

Inconsistent Shadows

Frames of Reference, A. Garcia (2000)

Inconsistent Shadows

Reference photos illustrate why the shadows are inconsistent in the final image.

Inconsistent ShadowsThis fake cutting that circulated during the 2004 Presidential primaries combined a photo of John Kerry was taken 1971 with one of Jane Fonda taken in 1972.

The form shadows on their clothes are clearly inconsistent.

Next LectureReflection

Homework #11 (Building a Scene in Maya)Due next Tuesday

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