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Pick up a clicker, find the right channel, and enter Student ID. Upcoming Deadlines. Homework #12 –Cameras and Lights in Maya Due Tuesday, May 8 th (Next week) 20 points (10 points if late) Homework #13 – Creating Stereoscopic 3D Images Due Tuesday, May 15 th (Last day of classes)

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Upcoming deadlines

Pick up a clicker, find the right channel, and enter Student ID

Upcoming Deadlines

Homework #12 –Cameras and Lights in Maya

Due Tuesday, May 8th (Next week)

20 points (10 points if late)

Homework #13 – Creating Stereoscopic 3D Images

Due Tuesday, May 15th (Last day of classes)

20 points (10 points if late)

For full schedule, visit course website:

ArtPhysics123.pbworks.com


Homework 12

Homework #12

For this assignment you are given a photograph of a real object and you will try to match the camera and the lighting.

Each person will have a choice of four photos; for the assignment match any one of these photos (for extra credit, do more than one).

To find the photographs assigned to you, go to:

http://tinyurl.com/6uom7kp


Upcoming deadlines

Photo


Homework 121

Homework #12

The Maya model for this "widget" object has been created for you and may be downloaded here:

http://tinyurl.com/7zhsaf7

Open the object in Maya, create a surface for it to sit on, position the camera, add some lights, and adjust everything until your rendered Maya image looks as closely as possible to the photograph.

Try to match any colors, for the object and the lights, as well as the details of the shadows (e.g., penumbra angles, ambient light, drop-off).


Upcoming deadlines

Maya Render


Homework 122

Homework #12

To finish, move the position of your camera to view the scene from another direction (suggest that you turn the camera roughly 45 degrees to either side).

Render #1

Render #2


Homework 123

Homework #12

Finally, upload the photo you chose to use and the two Maya rendered images into a posting entitled "Recreating Cameras and Lights in Maya."

Note that this is a new assignment this year so there are no examples from previous semesters; contact me if you have any questions.

Due by 8am on Tuesday, May 8th

20 points (10 points if late)


Homework 124

Homework #12

Non-Maya Alternative: One of the four photographs is a pair of soup cans. Recreate the camera and lighting in that photograph as accurately as possible then take your own photos of the scene.

Finish by taking a second photograph with the camera at about 45 degrees to either side of its original position.

Upload both of your photographs as well as the photograph that you're matching.

Note that it will not be easy to duplicate the lighting conditions using common house lamps; only do this alternative if you find it absolutely impossible to work with Maya.


Final exam

Final Exam

Final exam is on Tuesday, May 22nd from 1215 to 1430 in this classroom.

Final Exam will have of 10 short essay questions on material covered in lecture.

Final exam counts for 50 points.

You may bring one page of notes double-sided (or two pages single-sided) to the exam.


Final exam1

Final Exam

Visit the course website for more info on your final exam (including sample).

Note that the final exam is optional.

All Assignments and Extra Credit must be turned in by 5pm on May 22nd


Special event

Special Event

PIXAR presentation on "Brave" in Washington Square Room 109 at 3:30pm today.

Go immediately after class if you hope to get a seat!


Survey question

Survey Question

From which of these assignments did you learn the most:

  • Term papers

  • Homeworks using Tracker

  • Stop-motion animation homeworks

  • Homeworks using Maya

  • Reverse video reference


Review question

Review Question

Which path does light ray take after entering the water?

  • Path A

  • Path B

  • Path C

  • Path D

D

A

C

B


Law of refraction

Law of Refraction

C) Path C

Angle is smaller in the denser material.

The light ray bends but does not cross the normal (line perpendicular to the surface)


Review question1

Review Question

What looks like a pool of water in this photo is actually a mirage image of the sky created due to the desert heat.

  • Mirages are produced by:

  • Refraction

  • Reflection

  • Scattering

  • Miracles

  • Myopia


Mirages

Mirages

A) Refraction

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

Cool Air

Hot Air


Review question2

Review Question

Natural lighting underwater is primarily from overhead because sunlight cannot enter the water at more than about a 45 degree angle.

True or False?


Total internal reflection

Total Internal Reflection

True.

For the same reason you can only see the sky from underwater when looking up at more than about a 45 degree angle.

See sky

Mirror


Optics lighting part iv scattering

Optics & LightingPart IV: Scattering


Elements of optics

Elements of Optics

Reflection

Scattering

Eye-Brain

Light Source

Refraction


Dw consulting example

DW Consulting Example

Disco lights for Intel commercial


Basic scattering

Basic Scattering

Some sunlight is scattered, making the fog visible.


Scattering out scattering in

Scattering Out & Scattering In

To this viewer, the fog has scattered out some of the light so the sun isn’t as bright

To this viewer, the fog has scattered in some light so the fog is visible.


Scattering vs absorption

Scattering vs. Absorption

Scattering is a deflection of the light.

Absorption is an elimination of light.

40%

100%

50%

10%

For example, if 40% of the light is scattered and 10% is absorbed then 50% directly reaches viewer.


Extinction

Extinction

Extinction defined as absorption plus scattering.

40%

100%

40% scattered10% absorbed

50%

10%

10%

100%

10% scattered40% absorbed

50%

40%

Extinction is 50% in both cases.


Demo scattering vs absorption

Demo: Scattering vs. Absorption

Beakers filled with water placed on overhead projector.

Beaker has drop of white ink, the other has a drop of black ink.

?

What is seen on the screen?


Demo scattering vs absorption1

Demo: Scattering vs. Absorption

Glass dishes filled with water placed on overhead projector.

One dish has drop of milk, the other has a drop of black ink.

Projected image has two dark spots.

Black ink absorbs light.

White ink scatters light.


Particle sizes scattering

Particle Sizes & Scattering

Large Particles (Reflection/ Refraction)

Tiny Particles (Rayleigh Scattering)

Air

Birds

Cloud

Small Particles (Mie Scattering)


Particle sizes color

Rayleigh Scattering

Particle Sizes & Color

Tiny Particles – Scatter blue light the most, red the least; white light scattered with a hue shift to blue.

Gas fumes

Fine smoke

Particles smaller than wavelength of visible light.

Air molecules


Rayleigh scattering by color

Rayleigh Scattering by Color

Blue light: 440 nm

Green light: 550 nm

Red light: 660 nm

For tiny particles (under 400 nm) scattering is strongest for blue light and weakest for red light.

Scattering Strength

Particle Size

0 200 nm 400 nm


Tyndall scattering

Tyndall Scattering

Tyndall scattering is very similar to Rayleigh scattering since both are the scattering of light (especially blue light) by very small particles.

Blue iris

Opalescent glass


Demo aerogel opalescence

Demo: Aerogel Opalescence

Aerogel is ultralight, hard foam made from SuperGlue.

Scattering makes aerogel look blue while the transmitted light is yellow.

Flashlight shines white light on a piece of aerogel


Particle sizes color1

Mie Scattering

Particle Sizes & Color

Small Particles – Scattering of hues varies with particle size, usually averaging out to white.

White paint

Milk

Particles comparable to wavelength of visible light.

Clouds


Mie scattering by color

Mie Scattering by Color

Blue light: 440 nm

Green light: 550 nm

Red light: 660 nm

For small particles Mie scattering strength varies greatly with the particle size.

Since particles tend to be a mix of sizes, all hues are scattered equally resulting in white.

Scattering Strength

Particle Size

400 nm 800 nm 1200 nm


Particle sizes color2

Particle Sizes & Color

Confetti

Large Particles – Reflect light off the surface or, if transparent, refract and transmit light.

Sand

Particles much larger than the wavelength of visible light.

Rain


Suspended particles

Suspended Particles

A dust storm is seen from the reflection off the suspended dust particles rather than true scattering.

Mie scattering by water droplets in clouds.

Reflection from suspended particles.


Volumetric lighting

Volumetric Lighting

Volumetric lighting is used to create the volume of scattered light, usually due to Mie scattering in dust or fog.


Scattering angle

Scattering & Angle

Direction of light scattering is not random.

Forward

Backward

More light

Less light


Mie scattering angle

Mie Scattering & Angle

Mie scattering is strongest in the forward and weakest backward directions.

Fog


Mie forward scattering

Mie Forward Scattering

Sun

Sun is behind the fog in this photo

Fog

Mie scattering from drier fog

Drier Vent

Camera


Mie backward scattering

Mie Backward Scattering

Sun is behind the camera in this photo

Fog

Camera

Mie scattering from drier fog

Drier Vent

Sun


Sun rays

Mie scattering by fog mist

Sun Rays

Intensity of sun rays varies with the angle between sun and viewer.

Notice that the light on the ground is bright even though the ray’s intensity appears to taper off along the sun ray.

To camera

To camera


Rayleigh scattering angle

Rayleigh Scattering & Angle

Rayleigh scattering is strongest in the forward and backward directions.

It is weakest to the sides (90 degrees).

Gas fumes


Brightness of the sky

Brightness of the Sky

The darkest part of the sky tends to be about 90 degrees from the direction of the sun.

Rayleigh scattering by air molecules

From Sun


Single vs multiple scattering

Single vs. Multiple Scattering

Light rays may scatter multiple times, if the scattering medium is dense.

Light Fog

Heavy Fog


Demo scattering in a fish tank

Demo: Scattering in a Fish Tank

Single versus multiple scattering is nicely shown by shining a flashlight into an aquarium filled with clean water then adding more and more milk.


Single scattering in a fish tank

Single Scattering in a Fish Tank

Single scattering produces a narrow beam of light.

Flashlight

Mie scattering by very dilute water/milk mix.


Single scattering in a fish tank1

Single Scattering in a Fish Tank

Intensity differences due to scattering angle (i.e., near the light we have more forward scattering).

Flashlight

To camera

To camera


Multiple scattering in a fish tank

Multiple Scattering in a Fish Tank

Multiple scattering produces a diffuse beam of light.

Flashlight

Hue shift from white (near flashlight) to orange-red on the opposite side.


Scattering in a fish tank

Scattering in a Fish Tank

With single scattering only particles in the direct beam are scattering the light.

To camera

With multiple scattering particles outside the beam are illuminated by light scattered from out of the beam.

To camera


Optical thickness

Optical Thickness

Total scattering depends on optical thickness.

20%

100%

80%

40%

100%

60%

Demo: Beaker on projector; fill with milky water


Shadows multiple scattering

Shadows & Multiple Scattering

With multiple scattering the side opposite from the light can be in shadow.

Shadows


Atmospheric perspective

Atmospheric Perspective

Objects in the distance have a bluish, unsaturated color due to combination of Rayleigh, Tyndall, and Mie scattering.


Atmospheric perspective1

Atmospheric Perspective

Far away mountains can have a bluish ting due to blue light scattered in by Rayleigh scattering

From Sun

Weak scattering but big optical depth


Atmospheric perspective example

Atmospheric Perspective Example


Fog and smog

Notice clock face

Fog and Smog

Atmospheric perspective can remove all contrast for distant objects, turning them into silhouettes.


Perspective of color

“Perspective of Color”

Not only did Leonardo da Vinci make good use of what he called “Perspective of Color” but he also correctly predicted that this is why the sky is blue.

The Virgin and Child with Saint Anne, 1510

La Gioconda, 1503-06

The Virgin of the Rocks, 1482


Underwater perspective

Underwater Perspective

Water is transparent but absorbs red light about x100 more than blue light.

Objects in distance are bluish but saturated.

Significant reflection by suspended particles.

Particles are easily mixed in water due to buoyancy.


Sunrise sunset

Sunrise & Sunset

At sunrise and sunset the rays from the sun pass through a thick layer of atmosphere so Rayleigh scattering removes much of the blue light.


Next lecture seeing color

Next LectureSeeing Color

Homework #12Recreating Cameras and Lights in Maya

Due Tuesday, May 8th (Next Tuesday)

Please turn off and return the clickers!


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