1. Upcoming Deadlines Fifth Homework (Video Analysis of a Jump) Due Wednesday, Feb. 24 th (Next week) 15 points (10 points if late) Sixth Homework (Stop-motion Animation) Due Wednesday, March 3 rd (In two weeks) 20 points (if late, 10 points) Bonus prize of 20 extra points to top three. For full schedule, visit course website: ArtPhysics123.pbworks.com Pick up a clicker, find the right channel, and enter Student ID

2. Activating your Clicker * Turn on your clicker. * Enter the channel number or letter for joining this class. Hit Enter/Send key. * Clicker should read AP123S258 * 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.

3. Extra Credit Opportunity Go to any event at Cinequest Film Festival in downtown San Jose. Turn in proof of attendance (receipt, photos, etc.) for 5 points of extra credit.

4. Extra Credit Opportunity Student registration is $75 (ouch) Turn in your receipt for 10 points of extra credit. For info: www.gdconf.com Attend the Game Developer’s Conference in San Francisco, on Saturday, March 13 th

5. Homework Assignment #5 In this assignment you’ll again use Tracker software to analyze the motion of a moving object from video reference. First, shoot some reference of yourself doing a running jump. Position your camera so that you're in frame the entire time that you're in the air. Stage the jump to be in profile. Shoot at least 5 takes, even if they are more or less the same.

6. Homework Assignment #5 Original Video Reference

7. Homework Assignment #5 Import your video reference into the Tracker software (as in previous homework). Track the center of your waistline or beltline, which is approximately the location of your center of gravity. Marking your position from the time you leave the ground until you’ve landed. After tracking your motion, upload the screen image from Tracker to your blog into a post called "Video analysis of path of action".

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

9. Homework Assignment #5 Finally, rewind your video to the first frame of your jump and from the "File" menu select "Record -> Quicktime Movie". Hit the play button and allow the clip to play until the end of your jump. Next, in the "Capturing Quicktime MOV" window click "Save As" to save the recording.

10. Homework Assignment #5 Video Reference with Tracking

11. Homework Assignment #5 Check that your saved Quicktime movie has the track showing the path of action then put both clips (original and with tracking) in your blog post using YouTube or Vimeo. This assignment is due by 8am on Wednesday, Feb. 24 th (week from today). 15 points (10 points if late)

12. Survey Question So far the pace of the class has been: A)Too fast B)A little fast C)About right D)A little slow E)Too slow

13. Review Question The motion graph for a ball drop, going from the apex until the ball just touches the ground, looks like: A)B)C)D)

14. Motion Graph of a Ball Drop Frames Height D)

15. Arcs in Animation

16. Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation. 1.Squash & Stretch 2.Timing 3.Anticipation 4.Staging 5.Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7.Slow In and Slow Out 8.Arcs 9.Exaggeration 10.Secondary Action 11.Appeal

17. Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation. 1.Squash & Stretch 2.Timing 3.Anticipation 4.Staging 5.Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7.Slow In and Slow Out 8.Arcs 9.Exaggeration 10.Secondary Action 11.Appeal We have already discussed several of these principles of animation, specifically:

18. Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation. 1.Squash & Stretch 2.Timing 3.Anticipation 4.Staging 5.Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7.Slow In and Slow Out 8.Arcs 9.Exaggeration 10.Secondary Action 11.Appeal Today we will discuss arcs and how they relate to animated motion.

19. Arcs of Motion Motion usually follows an arc, which may be simple, like a circle, or very complex and irregular.

20. Importance of Arcs One of the major problems for the inbetweeners is that it is much more difficult to make a drawing on an arc. Drawings made as straight inbetweens completely kill the essence of the action. Disney animation legends Frank Thomas and Olie Johnston write: Wrong Right

21. Circular Arcs Circular arcs are common since motion is often around a fixed pivot point, such as a joint.

22. Speed in Circular Motion Rotational Speed: Revolutions per second Tangential Speed: Total distance per second Same Rotational Speed Different Tangential Speeds

23. Throwing Arm Tangential Speed The longer the throwing arm, the greater the tangential speed so the farther it can throw. Sling lengthens the arm at almost no cost in the weight. Doubling the speed quadruples the range! x2

24. Timing on Circular Arcs In this golf swing the motion: Slows out (accelerates) to hit the ball Uniform after the hit Slows in as the swing finishes follow-through A circular arc is a simple path of action but the timing may be complex and textured. Slow out Uniform Slow in

25. Non-Uniform Circular Motion Two common types of motion on circular arcs that have non-uniform timing and spacing are: Exponential SpacingPendulum Spacing Example: Tipping over Example: Stride in walking

26. Tipping Over Tipping over is a common example of motion on a circular arc. Two ways to tip over: X X Center tipped past point of contact Center past an edge

27. Tipping Rotation A brick rotates about a point as it tips; that point is the center of a circular arc. X X Friction tends to keep the brick from sliding until it loses contact with the table. X X

28. As the slope of the incline increases, the acceleration itself accelerates. Exponential Spacing 1 3 7 1 2 3 4 Constant acceleration (Odd Rule) Release 5 1 2 3 4 Exponential Spacing

29. Slowing out from a tipping point is very slow initially, but then accelerates rapidly. Rolling off a Tipping Point 1 2 3 4 5 6 7 8 Peak

30. Video Reference of Tipping Brick http://www.youtube.com/watch?v=otYAYMZ4iGg

31. Anticipation & Exponential Spacing Texture of the timing as the brick tips over creates anticipation, which you want at the start of a scene Also notice motion blur near top of brick, which has large tangential speed.

32. Pendulum Spacing A pendulum’s path of action is also a circular arc but the spacing is very different from the exponential spacing of tipping over.

33. Spacing & Timing in Swinging A pendulum will slow in and out as it swings back and forth, the same as a ball rolling in a half-pipe. Most of the texture in the timing is at the endpoints; the timing is even in the center.

34. Pencil Test Example http://www.youtube.com/watch?v=xuoJdNGxffU

35. Motion Graph for Pendulum The motion graph (angle vs. frame) shows that the timing is mostly textured (curves the most) at the apexes. Frame Angle #1 #4 #7 FAST SLOW SLOW, again SLOW, again Ball goes fastest around the bottom but the speed is almost constant.

36. Uniform Rotation in Perspective The timing for uniform rotation has texture when seen in perspective. Half orbit Quarter orbit Rotation from key #1 to #5 in background takes twice as long as from #6 to #8 in foreground.

37. Swinging in Perspective Visually the timing has even more texture when the swing occurs in perspective.

38. Who Framed Roger Rabbit? (1988) The opening sequence in Who Framed Roger Rabbit? makes great use of the textured timing of arcs in perspective. Animation by Richard Williams

39. Who Framed Roger Rabbit? (1988) http://www.youtube.com/watch?v=sLNqtU-gYPc

40. Demo: Don’t Flinch Pendulum swings back and forth yet it doesn’t hit your face.

41. Bowling Ball Pendulum This video clip lets you experience what it’s like to do this demo. Click http://www.youtube.com/watch?v=UNsD15GjWWE

42. Spirals A spiral is just a circular arc with a radius that’s either increasing (spiral out) or decreasing (spiral in). Concept art from Pirates of the Caribbean 3

43. Rotational Speed in Spirals If the radius decreases without pulling the object inward then the rotational speed increases (due to shrinking radius) but the tangential speed stays constant. Spiral In Spacings along the curve stay constant.

44. Demo: Interrupted Pendulum Tangential speed does not increase due to the pendulum whipping around the interrupt bar. Energy is not increased by the interrupt bar so ball swings back to the same spot. Bar An “interrupt” bar changes the radius of the arc for a pendulum.

45. Rotation in Spirals (cont.) If the radius decreases by pulling the object inward then the rotational speed increases due to shrinking radius and due to an increase in the tangential speed. Spiral In Spacings along the curve get bigger and bigger.

46. Demo: Skater’s Spin Slow Rotation FAST Rotation Exert a force to pull hand weights toward my body, causing a big increase in rotational and tangential speeds

47. Rotation in Spirals (cont.) If the tangential speed decreases (say by friction) but inward force constant then the rotational speed still increases. Spiral In Spacings along the curve get shorter yet it still spins faster and faster. Coin Vortex

48. Rotation in a Spirals In summary, typically as an object rotates in a spiral, the rotation speed increases as the radius decreases. So as radius goes down, the r.p.m.s go up. However the spacings may get longer, or shorter, or stay constant!

49. How Does the Brick Fall? Does the brick rotate and then fall down the side of the table? X X No! The brick does not fall this way. X X 4 3 2 1

50. Video Reference of Tipping Brick http://www.youtube.com/watch?v=otYAYMZ4iGg

51. Forces on the Tipping Brick X X The table pushes on the brick upward and towards the right. Gravity pulls downward Center of the brick shifts down and towards the right. If no table…

52. Pushing Off by the Table The table pushes away on the brick, which causes the brick to move away from the table as it falls. X X X Once it loses contact with the table, only the force of gravity accelerates the brick.

53. Centrifugal Force What we see What the insect feels Insect inside a can rotating in a circle When we move on an arc, it seems to us as if there is an outward force, pushing us away from the center of the circle. Physicists call this apparent force the centrifugal force.

54. Class Demo: Bucket Overhead I will put a bucket full of water over my head without getting wet. How? Centrifugal Force By rotating it fast enough. The water stays in the bucked as if pressed into it by a centrifugal force. You experience centrifugal force on taking a sharp turn

55. Wile E. Coyote & Loop-D-Loop Watch carefully as Wile E. Coyote travels in a circle around a natural arch bridge. http://www.youtube.com/watch?v=p4YxdXw9evc From “Beep Beep” (1952)

56. Wile E. Coyote & Loop-D-Loop In reality, it is impossible to travel upside-down, as Wile E. Coyote does in this scene. True or False? “Beep Beep” (1952)

57. 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.

58. Demo: Loop-the-Loop If the speed of the ball is large then not only does it stay on the track, the ball even pushes outward and against the rail. Velocity Release

59. GAP Demo: Loop-the-Loop Ball could even circle a loop with a gap, if the speed was just right so gravity was equal to the centrifugal force. Velocity Release

60. Simulated Gravity Centrifugal force could be used to simulate gravity in a space station. With the appropriate rotational speed a person on the outer rim would feel as if they stood on the surface of Earth. Scientifically accurate in the movie 2001: A Space Odyssey (1968) Rotation

61. 2001: A Space Odyssey (1968)

62. Simple Spinning 1 5 7 3 1 Arbitrary 2 3 4 In simple spinning, the angle rotates at a constant rate. A brick tipped 45º as it loses contact with the table will fall spinning about 30º every two frames. A falling brick may turn by simple spinning around its center.

63. Tumbling 1 5 7 3 1 Arbitrary 2 3 4 There is no simple way to describe tumbling. However, the brick’s center still follows the same parabolic path of action. A falling brick may also turn by a more complicated tumbling motion.

64. Tennis Racket Theorem When an object turns about its long or its short axis, it tends to spin. When an object turns about its middle axis, it may tumble. SPIN TUMBLE

65. Irregular Objects SPIN TUMBLE SPIN TUMBLE

66. Spin or Tumble? Rotation around two of these axes is spinning. The axis of rotation that tumbles is: A)Head-to-toe axis B)Side-to-side axis C)Front-to-back axis A B C

67. Spin or Tumble? B) Side-to-side axis B Rotating along this axis typically results in irregular tumbling. Spinning is possible but requires more control than along the other two axes.

68. Rolling & Slipping 1234567 Rolling ball turns one revolution when it travels a distance equal to three times its diameter (actually 3.1416 diameter) ROLLING 12345 SLIPPING Slipping and rolling are both uniform in spacing and rotation.

69. Next Lecture Creating Action By Wednesday of next week: Complete the 5 th homework (Video analysis of Path of Action) Please return the clickers!