1. Upcoming Deadlines Fifth Homework (Video Analysis of a Path of Action) Due Tuesday, Sept. 18 th (Next week) 15 points (10 points if late) Sixth Homework (Stop-motion Animation of Falling) Due Tuesday, Sept. 25 th (In two weeks) 20 points (if late, 10 points) Bonus prize of 20 extra points to top three. For full schedule, visit course website: www.Animation123.com Have clickers ready

2. Homework Assignment #5 Use Tracker to analyze the motion of yourself doing a running jump. Shoot reference with at least 5 takes. Track the center of your body (center of torso at about the beltline) in the air. Upload original video, screen shot with graphs, and the video with tracking*. This assignment is due by 8am on Tuesday, Sept. 18 th (next week). 15 points (10 points if late) *May be tricky

3. Homework Assignment #5 Parabolic Path of Action Straight Line Parabolic Curve

4. Homework Assignment #5 Video Reference with Tracking

5. Survey Question How is the pace of the course so far? A)Much too Fast B)A little Fast C)About Right D)A little Slow E)Much too Slow Note: You score 1 point of credit for answering survey questions, regardless of your answer.

6. Review Question The timing and spacing for a brick tipping over is very similar to that of a leg swinging forward in a walk.A) True or B) False?

7. Review Question False. Tipping over has exponential spacing (increasing acceleration and speed) but a leg swinging forward has pendulum spacing (increasing speed, decreasing acceleration). Exponential Spacing Pendulum Spacing Example: Tipping over Example: Stride in walking

8. Review Question In reality, it is impossible to travel upside-down, as Wile E. Coyote does in this scene. A) True or B) False? “Beep Beep” (1952)

9. Wile E. Coyote & Loop-D-Loop False. If his speed is high enough then he stays in contact with the arch, just like the water in the spinning bucket.

10. Creating Action

11. Why Things Move So far we’ve only looked at how things move (slowing in/out, path of action, arcs, etc.). Now it’s time to look at why things move, that is, what causes action. The short answer is forces. To understand why things move the way they do, you need to consider the forces at play.

12. Newton’s Laws of Forces Newton established three basic laws to explain how motion is caused by forces: Law of Inertia Law of Acceleration Action-Reaction Principle Disney and other early animators rediscovered these laws of forces in their studies of motion. Sir Isaac Newton

13. Follow-Through When a character stops, it doesn’t suddenly freeze. Some parts of the character stop abruptly while others, such as arms, long hair, clothing, etc., continue moving for a few frames. In animation, this is known as follow-through. In physics, we know it as Newton’s Law of Inertia.

14. Motion, with & without Forces An object moves with constant, uniform motion until acted on by a force. No force An asteroid floats in space with a constant speed unless gravity deflects its motion. FORCE

15. Balance of Forces Rarely are there no forces but often forces are balanced so they “cancel” each other out. Important: Balanced forces does not mean that there’s no motion! Gravity Tension Floor

16. Law of Inertia Newton’s Law of Inertia says: An object moves with constant, uniform motion until acted on by an unbalanced force. Gravity Floor The bowling ball moves with constant speed* *In reality, there is a small unbalanced force, friction, that does slow the ball’s speed.

17. Home Demo: Riding the Bus When a moving bus halts, you continue moving forward.

18. Inertia & Drag Hair remains in motion even after the head stops moving, which is follow-through due to inertia. Before the bus stopsJust after it stops

19. Shoot ‘Em Up (2007) If the crash occurs at 35 miles per hour then the hero flies off at a speed of about 2 feet per frame.

20. Shoot ‘Em Up (2007) Frame 438 Frame 439 Frame 440 Frame 441 Stuntman flies out the window at about 10 m.p.h. This is a bit slow but at a realistic speed the audience wouldn’t see the action.

21. Shoot ‘Em Up (2007) Frame 459 Frame 460 Frame 461 Frame 462 Stuntman flies into the van at about 5 m.p.h. Noticeably much too slow but the sequence is outrageous anyway, so it works.

22. The League of Extraordinary Gentlemen (2003) In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet. http://www.youtube.com/watch?v=n8SDdkKSqns

23. A)Roll forward from where he lands, in the direction of the moving car. B)Roll backwards from where he lands. C)Land just as he does in the movie; this was actually done by a stuntman. The League of Extraordinary Gentlemen (2003) In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet. In reality, he would:

24. A) Roll forward You are moving at the same speed as the car when you jump out so you will roll forward. Jumping out of a Car Your path You’ll start losing speed after you hit the ground so, relative to the car, you’ll fall behind as the car continues speeding along. car

25. Law of Inertia (cont.) Newton’s Law of Inertia also says: An object at rest (not moving) remains at rest until acted on by an unbalanced force. Gravity Floor A stationary bowling ball remains stationary until some unbalanced force comes along. This is nothing more than motion at constant speed but with speed equal to zero.

26. If the bus starts moving again, you remain stationary, seemingly thrown backwards. Home Demo: Riding the Bus (cont.)

27. Inertia & Drag When the bus accelerates forward, the character’s hair drags behind due to inertia. Before the bus starts Just after it starts

28. As seen by observer sitting in the bus Frame of Reference As seen by observer on the street Bus Moves Background

29. Space Balls (1987)

30. Jackass (2002) http://www.youtube.com/watch?v=V-dFVdhgSsc

31. Class Demo: Tablecloth Pull Yank quickly Due to the vase’s inertia it remains at rest since almost no force acts on the vase if one pulls quickly and straight.

32. The centrifugal force you experience on taking a sharp curve is nothing more than inertia keeping you moving forward in a straight line. It feels as if you’re pulled to the outside bank of the curve. Centrifugal Force Revisited Your path

33. Inertia & Drag An object won’t move until a force acts on it so long hair trails behind as head turns. Although this is due to the hair’s inertia, in animation it’s usually called drag. An object at rest remains at rest until acted on by a force.

34. Drag in Arcs and Waves Animation drag is very noticeable when something like hair or cloth moves in an arc or in a wave-like motion.

35. Fukkireta http://www.youtube.com/watch?v=NFep4vO4TRc

36. Class Demo: Hula Skirt The motion of a hula skirt is an excellent example of animation “drag.” Also notice how the skirt moves outward as it turns due to centrifugal force.

37. Flour Sack Exercises The sack drop and sack pantomime are common animation exercises. A flour sack is a good proxy for learning character animation since it shows follow-through and drag. Dancing with the Sacks

38. Importance of Follow-through & Drag “Now we could use Follow-through on the fleshy parts to give us the solidity and dimension, we could drag the parts to give the added feeling of weight and reality. It all added up to more life in the scene. The magic was beginning to appear.” From The Illusion of Life - Disney Animation Notice the subtle follow-through in the hands, skirt, and pant legs for the last drawing of the Moving Hold. By Ham Luske

39. Newton’s Laws of Forces Newton established three basic laws to explain how motion is caused by forces: Law of Inertia Law of Acceleration Action-Reaction Principle The Law of Inertia explains motion without forces (or with only balanced forces). The Law of Acceleration explains motion with unbalanced forces. Sir Isaac Newton

40. Leaf/Paper Drop Test Animate a leaf (or piece of paper) drifting slowly to the ground. That was not a good leaf drop Let’s see some good ones by Gloria Cho and Katie Corna.

41. Leaf Drop Test http://www.youtube.com/watch?v=mbMo4HFJC1Y

42. Paper Drop Test http://www.youtube.com/watch?v=vKf-vIDSIik

43. Air Resistance Air resistance is a force created when an object moves through air. Depends on: Size (area) of the object Speed of the object Larger the size or speed, larger the resistance. Air Resistance Gravity

44. Demo: Hand out the Window Experience the force of air resistance by holding your hand out a car window. Resistance increases as speed increases. Resistance increases as area increases.

45. Demo: Falling in a Vacuum Feather falls slowly due to air resistance force. If we remove the air (create a vacuum) then feather and coin fall with same acceleration.

46. Home Demo: Drop the Sheet A flat sheet of paper falls slowly because of air resistance. What happens if we place it on top of a book, blocking the air from reaching it? Air Resistance Weight Book and sheet fall together

47. Falling on the Moon There’s no atmosphere and thus no air resistance on the Moon. http://www.youtube.com/watch?v=5C5_dOEyAfk

48. Falling with Air Resistance 1 3 5 5 5 Accelerating Motion Uniform Motion Light objects, such as a beach ball, initially fall with accelerating motion. Due to air resistance, the motion transitions to uniform motion after falling a certain distance. 5

49. Terminal Speed Speed of falling objects increases until air resistance force balances gravity force. When forces balance, zero acceleration so constant speed. This is the terminal speed, the maximum speed when falling. Heavier parachutist has higher terminal speed

50. Wile E Coyote with Anvil The accident-prone Wile E Coyote walks off a cliff carrying an anvil. If he lets go of the anvil, he’ll fall: A)Slower B)Faster C)At the same speed

51. Wile E Coyote with Anvil The answer is: A)Slower You reach terminal speed when the force of air resistance balances your weight. The less you weight, the less air resistance is needed so the terminal speed is also lower (lower speed lower air resistance).

52. Estimating Terminal Speed Air Resistance Gravity Terminal speed of a rectangular object (with the density of water) falling flat is approximately: (Speed) = (50 m.p.h.) x  T where T is thickness in inches. Thickness, T TT Terminal Speed 1 / 100 inch 1 / 10 5 m.p.h. ¼ inch½25 m.p.h. 1 inch150 m.p.h 4 inch2100 m.p.h. 9 inch3150 m.p.h T

53. Terminal Speed & Thickness Piece of paper falls much faster when you drop it sideways instead of face-down. Air Resistance Gravity Air Resistance Small thickness; Slow terminal speed Big thickness; Fast terminal speed

54. Terminal Speed & Shape Terminal speed of aerodynamic shapes, like a sphere, are about 50% faster than for a rectangle. For example, the terminal speed of a raindrop with a radius of 1/8 th inch is about 20 m.p.h. Large raindrops are flattened due to air resistance and very large drops are split into smaller drops by the force of air resistance.

55. The Incredibles (2004) http://www.youtube.com/watch?v=j2SmaI6iPxA What is unrealistic about the way objects fall in this scene?

56. The Incredibles (2004) They land in the water… … chat for 10 seconds… … and then fuselage lands! Fuselage should have landed before they reached the water.

57. Terminal Speed & Density The denser the material, the higher the terminal speed. The table gives the terminal speed for density of water. The terminal speed for wood is about the same as for water since the density of wood is close to that of water. The terminal speed for rocks is about 50%-75% larger since rocks are 2-3 times denser than water. Metals, like iron and copper, are 8-9 times denser than water so the terminal speed is about three times larger. For example, a brick’s terminal speed is about 100 m.p.h. (Falling flat so thickness is 2 inches)

58. Leaf/Paper Terminal Speed The terminal speed of a leaf or sheet of paper is about 5 feet per second, which is about 3½ miles per hour (or 2-3 inches per frame). Terminal speed is reached after falling about 4 frames (flat orientation). Air Resistance Gravity

59. Falling Coffee Filter Tracked falling of a coffee filter. Distance Fallen Time Accelerates in first 1 / 3 second Constant Speed Click

60. Air Resistance Threshold Distance fallen from apex Speed (miles per hour) 1 foot5 4 feet10 9 feet15 16 feet20 25 feet25 49 feet35 100 feet50 400 feet100 900 feet150 Air resistance is only noticeable once an object’s speed gets close to its terminal speed. This table gives the speed of an object from the distance it’s fallen it there is no air resistance. For example, since a brick’s terminal velocity is 100 m.p.h. then air resistance is not noticeable for a 100 foot drop.

61. Balloon Drop Because the water balloon falls faster, the air resistance force on a water balloon is greater than on an air-filled balloon! However, a few ounces of air resistance force is insignificant for a water balloon weighing several pounds. Water Air Gravity Air Resistance

62. Cat Drop Video Reference http://www.youtube.com/watch?v=YJy17-BHQXg

63. Cat Drop Motion Graph Good parabolic arc; no noticeable air resistance

64. Cat Drop from Building Dropping a cat from a height of 100 ft (about 8 th floor) it reaches terminal velocity about half-way down. Height (feet) Frames No Air Resistance Terminal velocity 40 m.p.h. For cats, falling four stories is same as forty. Air Resistance Gravity

65. Surviving Falls from Heights Cats seem to have an uncanny ability to survive falls from high places. For example, cats have been known to survive falls of up to 32 stories. By contrast, dogs rarely survive falls of more than six stories. Humans usually die when they fall from such heights. From: www.animalhealthcare.ca In a study of cats that had fallen from up to 32 stories, an interesting finding emerged: while the rate of injury in cats seemed to increase linearly depending on the length of the fall, after seven stories, the rate of injury seemed to level off! In other words, the survival rate and severity of injuries were no more severe in a cat that fell seven stories than in one that fell 32 and in some cases, injuries were even less!

66. Surviving Falls from Heights (cont.) After further study, the reasons for this discrepancy became clear. When a person falls from a building, maximum speed or "terminal velocity" is reached after 32 stories. Cats, on the other hand, achieve terminal velocity at after falling only five stories! Until a cat reaches terminal velocity, it will experience acceleration and tend to reflexively extend its limbs, making it more susceptible to injuries. However, when a cat reaches terminal velocity, its vestibular system (i.e. the organs of balance) become less stimulated, causing the cat to relax. It will then orient its limbs more horizontally (splay- legged), thereby increasing air drag in much the same way a parachute does. In this posture, the force of impact also appears to become more evenly distributed. Don’t try this demo! Squirrels cannot die from a fall.

67. Home Demo: Keep It Up You can estimate the terminal speed as the wind speed needed to support the object.

68. Indoor Skydiving iflysfbay.com With a big fan (blowing 120-150 mph), you can experience terminal speed and skydive indoors.

69. Next Lecture Creating Action Part II For Tuesday of next week: Homework #5 (Video Analysis of Path of Action) Remember to turn off your clickers!