1. Upcoming Deadlines
Have clicker ready
First Term Paper The Laws of Physics in an Animation Universe Due Tuesday, October 9th (Next week) 100 points (50 points if late) Eighth Homework (Reverse Video Reference) Due Tuesday, October 16th (In 2 weeks) 20 points (10 points if late) For full schedule, visit course website:

2. Extra Credit Opportunity
Visit the Walt Disney Family Museum in SF to see the Between Frames: The Magic Behind Stop Motion Animation exhibition.
Exhibit runs Sept. 27, to April 28, 2013
Turn in proof of attendance (ticket receipt) for 10 points extra credit.
For info:

3. Extra Credit Opportunity
Visit the Exploratorium in San Francisco.
Turn in your ticket receipt for ten points extra credit.
Hours: Tuesday-Sunday: 10a.m.-5p.m
Location: 3601 Lyon Street, SF 94123
Next to Palace of Fine Arts complex

4. Extra Credit Opportunity
Visit the Cartoon Art Museum in SF to see the Avengers Assemble! or the The Art of ParaNorman! exhibits.
Avengers exhibit runs until Oct. 7th ; ParaNorman! exhibit opens Oct. 6th
Turn in proof of attendance (ticket receipt) for 10 points extra credit.
For info: cartoonart.org

5. Extra Credit Opportunity
Attend a screening or event at the Mill Valley Film Festival
(Oct. 4th -- 14th)
Turn in proof of attendance (ticket receipt) for 10 points extra credit.
For info:

6. First Term Paper Term paper is due by 8am on Tuesday, Oct. 9th
The required length of the term paper is 1500 words. Use a word count to verify that you are not significantly below this required length.
Upload your term paper to your blog in a post entitled "The Laws of Physics in an Animation Universe."
If you find that you significantly deviate from the outline, please add a brief explanation at the end of your term paper (which does not count towards the 1500 words).
Term paper is due by 8am on Tuesday, Oct. 9th
100 points (50 points if late)

7. SPECIAL OPTION
If you score 80 points or higher on your first term paper then you have the option of skipping the second term paper.
If you are eligible and select this option then you receive the same points for the second term paper as you did on the first paper.
If you are eligible but decide to turn in a second term paper anyway then your score will be no less that that of the first term paper.

8. Survey Question
The film that you have picked out for your first term paper is…
A) Animated feature film
B) Live action feature film with SFX
C) Mixed live-action and animation
D) Something other than a film
(TV series, video game, etc.)
E) Yet to be decided

9. Review Question When you raise your arms, your center of gravity…
Shifts upward
Shifts downward
Does not change

10. Human Center of Gravity
Shifts upward
X – Center
Of Gravity X X X X

11. Review Question
If a small amount of water is added to an empty soda can then the can may be balanced as shown.
The base of support is located around:
The top rim
Center of can
Near the bottom
The bottom edge
X A)
X B)
X C)
X D)

12. Home Demo: Balance the Can
D) The bottom edge
The water in the can allows you to balance the can by positioning the CG just above this base of support.
PEPSI
Base of support x CG
15-Feb-18

13. Weight Shift

14. Center of Gravity and Creating “Weight”
In today’s lecture we continue looking at how center of gravity affects affects static poses and dynamic action.
Also look at the issue of creating “weight.”

15. Center of Gravity & Path of Action
Path of action for the center of gravity is a parabolic arc

16. Rotation & Center of Gravity
Object’s rotation may be simple spinning or complex tumbling but that rotation occurs around the center of gravity.
The rotation is independent and separate from the center of gravity’s path of action.

17. Center of Gravity in Jumps
Corey Tom
For a jumping character the path of action for the center of gravity is a parabolic arc.

18. Jumping Swinging Arms & Legs
Examine this jump in which the arms and legs swing upward near the apex of the path of action.
Normal
Slo-Mo

19. Flattened Arc
The arc around the apex is flattened, which gives the illusion of floating or flying.
Due primarily to the swinging of the legs in this jump.

20. Shift of Center of Gravity
The center of gravity actually follows a parabolic arc. X X X
Track of the waistline is a flattened arc.

21. Shifting the Center of Gravity
By raising your arms and legs, you raise the location of your center of gravity (CG).
Lower torso CG CG
Near hips
Ballet dancers do this to create an illusion of floating.

23. Carrying a Weight
A heavy weight on a character’s back shifts the total center of gravity (CG) towards the rear.
The character will lean forward to keep the total CG over his Base of Support.
Alex’s CG X
Marty’s CG X X
A character has to lean forward when carrying a heavy weight on his back in order to keep the combined center of gravity above the base of support. In this image we can visually estimate the location of Alex and Marty’s individual centers of gravity. The combined total CG will be located between the individual CGs and will be proportionally closer to the heavier character.
Total CG

24. Carrying a Heavy Backpack
A heavy backpack shifts the CG towards the rear so a character needs to lean forward to keep it over their BoS.
Pack’s CG X X X
Total CG
His CG

25. Lifting a Weight This character is of normal human weight.
The ball she’s holding is:
Very light, like a beach ball.
Extremely heavy (she has super-human strength).
Either A) or B) above is possible.

26. Lifting a Heavy Weight Very Light. Heavy Ball No matter how strong the
Ball’s CG
No matter how strong the
character is, the pose
cannot be in balance if the ball is very heavy because the total center of gravity will not be above the base of support.
Imagine this as a free-standing statue; obviously it would tip over. X X
Total CG
Her CG X

27. Lifting a Light Weight
Light ball has little effect on the location of the total center of gravity.
CG X X X X
Center of gravity easily stays above her base of support

28. Lifting a Heavy Weight The water bottle brings the CG forward.X
CG X X X
Character leans back to keep the total CG above her feet

29. Lifting a Heavy Weight The water bottle brings the CG forward.
I hate my job.
The water bottle brings the CG forward. X
CG X X X
Character leans back to keep the total CG above her feet

30. Rising from an Armchair
To rise from a chair, you need to lean forward to bring your center of gravity over your feet.

31. Rising from an Armchair
If the chair has arms then you can extend your base of support to include your hands.
If the character stands up quickly then some of the poses may be out of balance. If so then the motion slows into the standing pose, much like a rising ball slows into its apex.

32. Breakdance Push-ups

33. Weight Shift
The scale closest to the CG supports a proportionally greater amount of weight.
Corey Tom

34. Weight Shift
The scale closest to the CG supports a proportionally greater amount of weight.
Corey Tom

35. Weight Shift in Characters
Alex is leaning such that his center of gravity is closer to the screen-left foot.
300 pounds X CG
When a character changes pose the character’s center of gravity shifts, causing a weight shift from one leg to another. Simply shifting the center of gravity by a few inches is enough to cause significantly weight shift.
Shoe illustration by Corey Tom
CoP
200
100
200
100

36. Demo: Weight Shift on Force Plate
Force plates are essentially digital bathroom scales that can be connected to a computer for collecting data.
Variation in weight is surprisingly large.

37. Weight Shift Measurements
Weight shift only requires a small shift in the location of the center of gravity
Corey Tom CG X
6 in.
6 in.
In this pose the weight on each leg is about the same; the center of gravity is positioned an equal distance from each foot.
Illustration by Corey Tom 90 90
12 inches
Equal weight on each foot
180
pounds 90 90

38. Weight Shift Measurements
Weight shift only requires a small shift in the location of the center of gravity
Corey Tom CG X
4 in.
8 in.
With just a two inch shift of the center of gravity the weight on each foot changes significantly.
Shifting the center of gravity by just two inches increases the weight to that side significantly; now the weight on the screen left foot is twice that of the weight on the other foot.
Illustration by Corey Tom
120 60
12 inches
2:1 ratio of weights
180
pounds
120 60

39. Weight Shift Measurements
Weight shift only requires a small shift in the location of the center of gravity
Corey Tom CG X
3 in.
9 in.
Shift the CG just one more inch and the ratio is now 3-to-1.
Shifting the center of gravity by one more inch now gives a 3-to-1 ratio of weights; notice the changes in the pose as the weight shift occurs.
Illustration by Corey Tom
135 45
12 inches
3:1 ratio of weights
180
pounds
135 45

40. Contrapposto
Notice the angles of the hips and shoulders and that they converge on the side that bears most of the weight.
Weight shifts from foot to foot are reflected by corresponding shifts in the hips and shoulders.
Donatello's bronze statue of David (circa 1440s)

41. Glenn Vilppu on Weight Shift
“By simply shifting the weight to one leg, we automatically create a curve in the torso, as we generally shift the rest of the torso to compensate. This shifting doesn't stop there, but extends to the neck and head, going up, which tends to move in the opposite direction again.” Glenn Vilpuu,

42. Standing vs. Sitting
Since weight shift changes the pose, you can tell whether a character is sitting or standing.
Katie Corna
In which scene are the characters sitting on a bench and in which scene are the characters standing?

43. Standing vs. Sitting
Since weight shift changes the pose, you can tell whether a character is standing or sitting.
Katie Corna

44. Illustrator Challenge
For illustrators, try this challenge at home:
Pick out some figure drawings (preferably your own) and make a copy with half the figure’s pose covered up.
Have a friend do the same and exchange drawings. Each of you should sketch in what you think the hidden half looks like.
Compare and think about why some poses read better than others.

45. Weight Gain and Loss
Take a heavy object in your palm and move it up and down; notice how the object’s weight changes.
Rising & Slowing Down: Lose Weight
Rising & Speeding Up: Gain Weight
Falling & Speeding Up:
Lose Weight
Falling & Slowing Down:
Gain Weight
With gravity
We think of an object’s weight as being constant but when the object accelerates its weight effectively varies. Specifically, if the object is:
Moving upward and gaining speed: Gain weight
Moving upward and losing speed: Lose weight
Moving downward and gaining speed: Lose weight
Moving downward and losing speed: Gain weight
This weight gain and loss is easily demonstrated if you take a heavy object, say a dumbbell or a large water bottle, and move it up and down. The object should be heavy enough so that you notice it’s weight, not just feel the contact with your skin. Another example is lifting a heavy bag of groceries by the bag’s handle; if you quickly pull upward the weight gain can be large enough to break the handle.
Dumbbell photo:
Against gravity

46. Dynamic Weight
Your weight on the ground varies as your body rises or falls, speeds up or slows down.
With gravity
Against gravity
With gravity
Against gravity
Corey Tom
Falling & Speeding Up:
Lose Weight
Rising & Speeding Up: Gain Weight
Rising & Slowing Down: Lose Weight
Falling & Slowing Down:
Gain Weight

47. Demo: Force Plate
Gain and lose weight by moving your body up and down. Can move the whole body or just part of it, for example your arms.
With gravity
Rising & Slowing Down: Lose Weight
Rising & Speeding Up: Gain Weight
Falling & Speeding Up:
Lose Weight
Falling & Slowing Down:
Gain Weight
Against gravity

48. “Counteraction” .

49. “Counteraction”
Richard Williams calls this effect of varying weight the counteraction.
Falling & Slowing Down:
Gain Weight
As a character moves (walks, runs, jumps, etc.) the changes in weight create many overlapping actions in the movement of hair, clothing, and flesh. Gaining weight pulls these downward while losing weight causes them to almost float. Richard Williams calls this effect “counteraction” and in The Animator's Survival Kit he writes, “When the character (accelerates) up – the drapery or hair or soft bits go down.” Poorly animated characters sometimes look “floaty” as they walk because their actions lack this variation in weight.
Book cover:

50. “Counteraction”
Richard Williams writes, “When the character goes up – the drapery or hair or soft bits go down.”
Lose Weight
Gain Weight
Lose Weight

51. Dynamic Balance
A pose that’s out of balance for a stationary character may be in dynamic balance if the character is moving.
Charlene Fleming

52. Tilting the Line of Gravity
Acceleration tilts the line of gravity.
Stationary or Steady Train
Accelerating
Train
Charlene Fleming

53. Stopping and Starting You lose balance on a sudden stop or start
since acceleration tilts the line of gravity.
Sudden stop
Sudden start
Fall towards the new Center of Pressure.

54. Leaning into a Turn
Centripetal acceleration tilts the line of gravity to the inside of the turn.
When a moving character turns a corner there's a change of momentum due to a centripetal force (see the principle of Momentum and Force). Remember that a change in momentum occurs when the direction of motion changes, even if the speed stays constant. Making a turn causes the line of gravity to tilt and characters will lean accordingly to stay in dynamic balance (e.g., a runner leans into a turn). The faster and/or tighter the turn, the greater the angle of the tilt.
Illustration by Charlene Fleming
Faster and/or tighter the turn, the greater the angle of the tilt.

55. “Roll Over” Loss of Balance
Car making a tight turn may lose balance due to tilting of the line of gravity caused by centripetal acceleration.
Tips Over
Centripetal
Acceleration X CG X CG
Similar to a car parked on a slope
Tight Turn

56. Centrifugal Force
Can view roll-over loss of balance in terms of the centrifugal force pulling the CG outward.
Centrifugal
Force
Centripetal
Acceleration X CG
Centrifugal
Force
Tight Turn
Weight

57. Quiz Question
Car takes a sharp, high-speed turn. Which side of the car dips downward?
A) This side goes down.
B) This side goes down. X CG
Tight Turn

58. Centrifugal Force
Centrifugal force pulls the CG towards the outside of the curve and, combined with the weight, it tilts the car.
Centrifugal
Force X CG
B) This side goes down.
Weight
Tight Turn

59. Bullitt (1968)
Watch the cars as they take high-speed turns.

60. Leaning In vs. Tilting Outward
Motorcycle riders actively lean into the turn to maintain dynamic balance.
Tight Turn
Car’s suspension is passive so centrifugal force tilts it outward.
Tight Turn

61. Leaning In vs. Tilting Outward

62. Leaning In vs. Tilting Outward
Car’s suspension is passive so centrifugal force tilts it outward.
When a car takes a high speed turn by the Law of Inertia the body of the car tends to continue traveling in the original direction, thus causing the car to tilt to the outside of the curve; this can also be thought of in terms of the centrifugal force, as experienced by the car.
On the other hand, motorcycle riders tend to lean into the turn thus tilting opposite from the tilting of the car, in order to maintain dynamic balance as they take the turn.
Motorcycle riders actively lean into the turn to maintain dynamic balance.

63. Radius of the Rotation
With constant rotation, the farther from the center the greater the centrifugal force.
Centrifugal
Force

64. Radius of the Turn
Going the same speed, the tighter the turn radius the greater the centrifugal force.
Same speed
Centrifugal
Force

65. Wall of Death
The Wall of Death stunt uses a circular pit with a tight radius.

66. Next Lecture Action / Reaction
First Term Paper
Due on Tuesday (Next week)