Directed by Friz Freleng from a story by Warren Foster.
Animation by Gerry Chiniquy and voices by Mel Blanc.
Won the Oscar for Best Short Subject (Cartoons) in 1956.

Upcoming
Deadlines
Pick up a clicker, find the right channel, and enter Student ID
Homework #13 – Creating Stereoscopic 3D Images
Due Monday, May 17 th (Last day of classes)
20 points (10 points if late)
Final Exam is at 12:15 on Wednesday, May 19th in this room.
All Assignments and Extra Credit must be turned in by 5pm on
Wednesday, May 19 th
There are no more furlough days for this class this semester.
For full schedule, visit course website:
ArtPhysics123.pbworks.com

Final Exam will have of 10 short essay questions on material covered in lecture.
Final exam counts for 50 points.
See course website for copy of last semester’s final exam.
You may bring one page of notes doublesided (or two pages single-sided) to the exam.

Interview with Kathy Altieri,
DreamWorks Animation artist
Tuesday, May 11 th at 2:30 p.m.
Morris Dailey Auditorium (Tower Hall) http://www.youtube.com/watch?v=vkwZ9kzrMN0

Activating your Clicker
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* Enter the channel number or letter for joining this class. Hit Enter/Send key.
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* Type in your student ID; hit Enter/Send.
Clicker is now ready to use; leave it on.
Hit any key to wake the clicker from sleep mode.

Survey Question
In the last homework assignment you will be re-coloring photos for 3D effects.
How much experience do you have using
Adobe Photoshop?
A) Never used it
B) Have used it only a little bit
C) Use it regularly
D) I am a Photoshop God

Finding the Highlight
Lamp
Where does Albert see the highlight reflected off this metal block?
A B
D: None of these
C
Albert

Finding the Highlight
Lamp
Albert
C Light rays from point C reach Albert.

Review Question
Matte surfaces, such as paper and cloth, are typically rendered in computer graphics using which shading model?
A) Phong
B) Blinn
C) Thong
D) Lambert
E) Mambo
Key only
Key + Fill

D) Lambert
Johann Heinrich
Lambert (1728–1777)
A Lambert surface scatters light diffusely so under directional light it looks equally bright from all angles.

Review Question
What is the shape of the mirrors in these photos?
A)
Concave Mirror
B)
Convex Mirror

Review Question
A) Concave Mirror
Image in concave mirror is magnified when original is close to the mirror.
Original
Mirror Image

Global Illumination
Advanced computer graphics uses global illumination algorithms to compute a more physically realistic rendering of a scene.
Without GI With GI
Notice focusing of light through glass sphere

Caustics are the bright concentrations of light caused by the focusing of that light when passing through a transparent object.
Caustics also create shadow patterns, such as the bright and dark pattern in a swimming pool, due to the deflection of the light.

Refraction
Light rays bend (refract) passing from water to air, making objects appear to be shallower and closer to the observer.
Observer sees image
Image
Image
Actual
Actual

Reciprocity
Light bends the same way whether it’s entering the water or coming out of the water.
Laser
This symmetry for light rays is called “reciprocity.”

Law of Refraction
Light passing from one material to another is refracted by an angle that depends on the optical density of each material.
Angle is smaller in the denser material.

Demo: Refraction thru a Block
Light is refracted entering the block and refracted back on leaving the block.

Optical density is given by the index of
refraction, n.
The larger the difference between the indices at an interface, the larger the angle of refraction for light rays crossing the interface.
Air
Water
Air
Glass
Air
Diamond n = 1.0
n = 1.3
n = 1.0
n = 1.5
n = 1.0
n = 2.4

Demo: Invisibility
Mineral oil and glass have nearly the same index of refraction
A glass rod is nearly invisible in a beaker of mineral oil.
A diamond, however, is easily seen.

Which path does light ray take after entering the glass wedge?
A)Path A
B)Path B
C) Path C
A
B
C
WEDGE

Path B
The angle always bends towards the perpendicular going from air to glass.
Notice that it bends away from the perpendicular going back out of the glass.
A
B
C
WEDGE

Mirages
Mirages are caused by the refraction of air because hot air has lower optical density than cold air.
Cool Air
Hot Air

When refraction angle exceeds 90º the light does not cross the surface.

Demo: Total Internal Reflection
Past the critical angle all the light is internally reflected.
Just below critical angle

Demo: Total Internal Reflection
Prism demonstrates total internal reflection if the angle of incidence is large enough.
No light escapes to this side
No light escapes to this side
No light escapes to this side

Looking up Underwater
Try this when you’re in the pool or the ocean next summer.
Looking straight up you see the sky but outside the 96 ° cone surface is like a mirror

Natural Lighting Underwater
Due to total internal refraction sunlight never enters the water at more than about a 45 degree angle.
Image seen underwater
Sun

Total internal reflection causes light to reflect inside a solid glass tube.

Curvature of a lens surface produces a continuous, variable angular refraction.
Concave lens shrinks its image
Convex lens magnifies its image

Demo: Concave Lenses
Curved surface of a concave lens causes light rays to diverge, dispersing the light and shrinking any images.

Demo: Convex Lenses
Curved surface of a convex lens causes light rays to converge, focusing the light and possibly magnifying images.

Demo: Real Image of Convex Lens
Image formed by convex lens can be observed on a screen.

Bokeh Effect (Lens Blur)
Point lights expand into balls of light when the light source is out of focus (outside the depth of field).
The term is from the Japanese word boke ( 暈け or ボケ ), which means "blur" or "haze."

Pinhole Camera
Small pinhole allows only small amount of light in, blocking overlapping diffuse rays and forming image inside the camera.

Demo: Pinhole Lens
Make a pinhole in a piece of cardboard.
You’ll find that you can focus better when looking through the pinhole.
This works best if you remove any corrective lenses, such as contacts and eyeglasses.

Camera Obscura
The camera obscura (room darkened) dates to ancient times; it was first detailed in the writings of Leonardo da Vinci.
A room is completely sealed from light except for a coinsized hole in one wall. An image of the outside world appears projected, upside down and reversed right-toleft, onto a wall opposite the opening.
Diffuse light

Camera obscura with a projecting mirror.
Mirror
Mirror
Next to the Cliff House, San Francisco

Johannes Vermeer (1632-75)
Common elements in his paintings and ray tracing analysis suggest that this great Dutch artist may have built a camera obscura in his studio.
The Music Lesson

Vermeer

Using a lens allows for more light to be focused on the camera screen or film.
No image (Diffuse) Camera obscura Camera with lens

The eye’s lens changes shape to focus the image onto light sensitive cells of retina.
Image is formed upside-down on the retina of the eye.

If eye’s lens is unable to form image on the retina, an object will appear out of focus.
Myopia Hyperopic

Eyeglasses
Lenses of eyeglasses restore visual acuity by combining with the eye’s lens to form focused image onto retina.
Eyeglasses began to appear in common use in the 13th century. They may have been invented in northern
Italy but Marco Polo reports them in China as early as 1275.
Detail of portrait of Hugh de
Provence, Tomasso da Modena, 1352
Pinhole glasses

Astigmatism
Astigmatism due to eye’s lens being elliptical, which causes the focus in the vertical to differ from horizontal.
Vertical focus
Astigmatism may be corrected using a cylindrical lens.
In this example, the lens focuses in the horizontal only since vertical is already in focus.

Separating Colors
Blue wavelength of light refracts slightly more than the red, creating rainbows.
Water
Droplet
Glass Prism

Rainbows are formed by refraction from many, many raindrops. The red part is always above the blue part.

Double Rainbow
Primary
Secondary

Diamonds are cut so as to create a beautiful jewelry by taking advantage of total internal reflection and high color dispersion (prism effect).

Objects in the distance have a bluish, unsaturated color due to atmospheric scattering of blue light (same as blue sky).

Atmospheric Perspective Example

“Perspective of Color”
Not only did he make good use of what he called “Perspective of Color” but
Leonardo also correctly predicted that this is why the sky is blue.
The Virgin of the Rocks, Leonardo, 1482

Light Scattering
Mie Scattering
Direct scattering by suspended particles, such as dust, fog, etc.
Rayleigh Scattering*
Refraction by random variations in a transparent medium.
For both types of scattering blue light tends to scatter more strongly than red light.
Also called Rayleigh-Brillouin Scattering*

Mie Scattering Examples

Rayleigh Scattering
Sky is blue due to Rayleigh scattering of sunlight in the atmosphere.
When it passes through a very thick layer all the blue is scattered out and we’re left with yellowish red.

Volumetric Lighting
Volumetric lighting is used to create the volume of scattered light, usually due to Mie scattering.

Alan Wake (2010)
Atmospheric effects are very important in
Alan Wake, an upcoming game for Xbox 360.
http://www.youtube.com/watch?v=F3WfXAanKOs

No homework due next week
Homework #13 due on Monday, May 17 th
(Last day of class)
Please return the clickers!