Upcoming Deadlines

1
Upcoming Deadlines

• Second Term Paper
• Wednesday, November 25th
• (Day before Thanksgiving no class that day)
• Homework 11 (Building a scene in Maya)
• Monday, November 30th (Monday after
  Thanksgiving)
• Homework 12 (Lighting a scene in Maya)
• Monday, December 7th (Last day of class)
• For full schedule, visit course website
• ArtPhysics123.pbworks.com

2
Guest Lecture
Prof. Raquel Coelho will give a special lecture
on lighting in computer generated images. In
class, Wednesday, Nov. 18th
Coelho has worked for studios such as Blue Sky
and PDI/Dreamworks, Wildbrain Inc and Tippett
Studio, as animator in films such as "Charlotte's
Web", "Hellboy", "The Spiderwick Chronicles" and
"Happy Feet".
3
Homework Assignment
For 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.
4
Homework Assignment
The 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
them touching the vertical wall.
5
Homework Assignment
This simple scene was created by Candice Downey.
6
Homework Assignment
Do not include anything else in the scene keep
it clean so that the two letters are distinctly
seen without any other distracting elements.
Most of your grade will be based on correctly
following these instructions however extra points
will be awarded to creatively constructed letters
and interesting compositions within the scene.
7
Homework Assignment
After downloading and installing Maya, watch the
tutorials on how to perform basic tasks. Build
your scene using polygon objects ("Polygons" tab)
and/or NURBS surfaces ("Surfaces" tab). When
the scene is complete, select the "Rendering" tab
and press the "Render Current Scene" button. Once
the scene looks like you'd like, in the Render
View window save it as a JPEG file and upload it
to your blog in an entry called "Building a Scene
in Maya." Save the Maya file containing your
scene since you'll need it for the next
assignment.
8
Homework Assignment
Alternative 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 Monday, November 30th. 20 points (if
late, 10 points)
9
Special Campus Event

• Animation Show of Shows
• December 7th
• (Monday)
• At 730 PM
• Morris Dailey
• Auditorium
• in Tower Hall
• FREE

10
Extra Credit Opportunity

• Visit the Alexander Calder exhibition at the San
  Jose Museum of Art.
• Exhibition runs through Dec. 13.
• Give me your ticket receipt for five points extra
  credit.

Big Red, 1959
Hours Tuesday Sunday, 11am - 5pm Admission
5.00 for students Location 110 South Market
St., Next to Fairmont Hotel, downtown SJ
11
Extra Credit Opportunity
Visit the Cartoon Art Museum in San Francisco to
see Once Upon a Dream The Art of Sleeping
Beauty.

• Exhibition runs through Jan. 10.
• Give me your ticket receipt for ten points extra
  credit.

Hours Tuesday Sunday, 11am - 5pm Admission
4.00 for students Location 655 Mission
StreetSan Francisco, California 94105 Near
Moscone Convention Center
12
Extra Credit Opportunity
Visit the Walt Disney Family Museum in San
Francisco (opens Oct. 1st).

• Give me your ticket receipt for ten points extra
  credit.

Hours Wednesday-Monday 10a.m.-6p.m Admission
15.00 for students Location 104 Montgomery
Street Inside The Presidio of San Francisco
13
Extra Credit Opportunity
Visit the Exploratorium in San Francisco.

• Give me your ticket receipt for ten points extra
  credit.

Hours Tuesday-Sunday 10a.m.-5p.m Admission
11.00 for students Location 3601 Lyon Street,
SF 94123 Next to Palace of Fine Arts complex
14
Optics LightingPart I Ray Tracing
15
Lighting
Lighting is important in all the visual arts,
from painting to cinematography.
Humphrey Bogart in The Maltese Falcon (1941)
The Orrery, Joseph Wright (1766)
16
Up (2009)
Lets look at how lighting in used in a a scene
from Pixars Up.
17
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.
www.andrew-whitehurst.net
18
Light Intensity Distance
The intensity of light decreases as we get
farther from the light source.
The light gets weaker because it is spread over a
larger area.
Light intensity decreases quadratically, that is,
at twice the distance you have a four times less
intensity.
19
Demo Perspective Cards

• Hold large card at arms 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
Arms length
Half
20
Area Distance
These four figures are equally spaced in distance
and, in perspective, you are standing that
distance from the first.
21
Light Intensity Angle
As 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.
5 light rays hit surface
7 light rays hit surface
22
Seasons of the Year
Northern Hemisphere is warm in July because Earth
is tilted towards the Sun.
Southern Hemisphere is cold in July since its
tilted way from the Sun. The seasons are
reversed in January.
Equator
23
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 objects curvature and
shape.
24
Shadows
Size and sharpness of a shadow depends on size
and distance of the light source and of the
object casting the shadow.
25
Shadows
No Shadow
An ant on the ground standing in the penumbra
could see part of the sun. Standing in the umbra
part of the shadow, the ant wouldnt see the sun
at all.
Penumbra
Umbra
26
Ray Tracing for Shadows
Trace rays from light source to wall to map out
location of deep shadow (umbra) and fuzzy shadow
(penumbra).
Light source
Object
Wall
27
Solar Shadows
The width of the penumbra for a shadow cast by
the Sun equals about 1 of the distance from the
object to its shadow.
Angle ½ degree
(
)
Penumbra
Sun
UMBRA
Distance
Floor
Diagram is not to scale
Object
28
Penumbra Size
Notice how the size of the penumbra increases as
the shadow gets farther from the base of the tree.
29
Inconsistent Shadows
The perspective in this painting is pretty good
but whats wrong with the shadows?
The Birth of the VirginFra Carnevale, 1467
30
Inconsistent Shadows
Variety of errors yet not immediately noticeable.
Rising shadows?
Downward shadow?
No shadows?
Long shadows from left to right
The Birth of the VirginFra Carnevale, 1467
31
Ambient Light
Ambient
Ambient
Direct
Direct
Most lighting is indirect, coming not from a
light source but from reflections off of other
surfaces.
Direct
Ambient
32
Fill Lighting
Key
KeyFill
Fill
With two-point lighting the fill light softens
the contrast by adding ambient light.
www.andrew-whitehurst.net
33
Rim Lighting
KeyFill
KeyFillRim
Rim
Adding a rim light shining from behind
distinguishes the foreground objects from the
dark background.
www.andrew-whitehurst.net
34
Three-point Lighting
Three-point lighting (Key, Fill, and Rim) is a
formula that Hollywood has used for years.
KeyFillRim
Rim
Three-point lighting usually looks good but
sometimes too good, that is, it seems fake.
From Casablanca (1942)
35
Specular and Diffuse Reflection

• Reflection from most surfaces is diffuse, with
  incoming light scattered in all directions.
• Reflection from mirror surfaces is specular, with
  light reflecting in one direction.

Mirror
Specular reflection
Diffuse reflection
36
Lambert Diffuse Reflection
The apparent brightness of a Lambert surface is
the same regardless of the observer's angle of
view. This is typical of matte surfaces, such as
paper and cloth. In computer graphics,
Lambertian reflection is often used as a model
for diffuse reflection. The visual effect is that
rotating or scaling the object does not change
the apparent brightness of its surface
Key only
Key Fill
37
Phong Reflection
Phong reflection is a surface model combining the
diffuse reflection of rough surfaces with the
specular reflection of shiny surfaces. Shiny
surfaces have small intense specular highlights,
while dull surfaces have large highlights that
fall off more gradually. The model also has an
ambient term to account for the fill lighting.
38
Law of Specular Reflection

• Angle of incidence equals angle of reflection

SPECULAR REFLECTION
39
Demo Blackboard Optics

• Special blackboard has mounted light source and
  mirrors.

Light Source
Demonstrates the Law of Reflection
Mirror
40
Ray Tracing

• Light ray from point A is reflected at point B
  and arrives at point B.

Notice the relationship between point B (where
the ray is reflected to) and point B (where the
ray would go if the mirror wasnt there).
41
Demo Who Do You See?
Which person in the front row sees the guy with
the hat in the mirror?
B
C
D
A
E
MIRROR
42
Demo Who Do You See?
Person A sees the guy with the hat when looking
in the mirror.
B
C
D
A
E
Diffuse light
MIRROR
The converse is also true Person E sees Person A
in the mirror.
43
Finding the Highlight
Lamp
Where does Abe see the highlight reflected off
this metal block?
Abe
A
C
B
D None of these
44
Finding the Highlight
Lamp
Abe
C
Light rays from point C reach Abe.
45
No Highlight for Diffuse Surface
Same amount of light from all points of a Lambert
diffuse surface.
Lamp
Abe
This end will be brighter only because its
closer to the lamp.
46
Diffuse Surface is Not a Mirror

• Light rays diffusely scatter in every direction
  from every spot on the surface.

Look at this spot on a diffuse surface
See a light ray from the top of your head
reflected from this spot. Also see light ray
from the tip of your nose reflected from this
spot.
47
Plane (Flat) Mirror

• Tracing light rays from original, to mirror, to
  eye allows us to construct image.

HAIR
NOSE
CHIN
Original
Mirror
48
Demo Pocket Mirror

• See full image of your head in a plane mirror
  thats half the size of your head.

Mirror
Image
Original
49
Image in the Mirror
Which work of art has a correct reflection?
Velazquez, Venus at her Mirror
Utamaro, Woman Powdering Her Neck
Incorrect
Incorrect
Helmut Newton, Bergstrom over Paris
Correct
50
Next LectureGuest LectureLighting in CG
Animation

• Campus closed on Wednesday Friday

Please return the clickers!