1. Upcoming Deadlines Homework #8 - Reverse Video Reference of Walking Due Wednesday, October 27 th (This Wednesday) 20 points (10 points if late); 20 point bonus to best for each clip Homework #9 – Stop-motion character Animation Due Wednesday, November 3rd th (Next week) 20 points (10 points if late); 20 point bonus to top 3 For full schedule, visit course website: ArtPhysics123.pbworks.com Pick up a clicker, find the right channel, and enter Student ID

2. Homework Assignment #9 In this assignment you will create a simple stop-motion animation of a moving character. For your character, use a doll or stuffed animal that's easily posed. You may even use an inanimate object, such as a table lamp, as long as you can animate it so that it looks like a character.

3. Homework Assignment #9 http://www.youtube.com/watch?v=EiEVdTQGGTM

4. Homework Assignment #9 Your animation should be composed of at least a dozen different images but you can use the same photo in two or more frames to get timing right. Try to make the motion of the character as realistic as possible so that your audience will momentarily forget that it's not actually alive. In homework assignment #6 you created a stop- motion animation of an inanimate falling object; if you're not happy with how you produced your earlier animation then re-read that assignment for alternative ways of creating stop-motion.

5. Homework Assignment #9 You may work together with one or more classmates to create a single animation for the team. Clearly indicate the work done by each person, for example if different persons animate different characters or different scenes. More is expected from a team effort; an animation created by a three person team should present three times as much work as a solo effort.

6. Homework Assignment #9 Post your animation clip to your blog in an entry entitled "Stop-Motion Character Animation.“ Assignment due 8am on Wed., November 3 rd 20 points (if late, 10 points) The top three clips in the class, as selected by another celebrity judge, will receive a bonus of 20 extra points.

7. Extra Credit Opportunity November 11–14, 2010 Landmark's Embarcadero Center Cinema http://www.sffs.org/Screenings-and-Events/Fall-Season.aspx Present proof of your attendance (receipt, photos, etc.) to any festival event or screening for 10 points of extra credit.

8. Special Campus Event Ron Diamond’s Animation Show of Shows Friday October 29 7:30 PM Morris Dailey Auditorium Free Admission

9. Activating your Clicker * Turn on your clicker. * Enter the channel number or letter for joining this class. Hit Enter/Send key. * Clicker should read AP123GF10 * 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.

10. Survey Question Many videos are shown in this class; would you say that the number of videos is: A)Too many. Use the class time for other stuff. B)About the right balance. C)Not enough. Add more and leave out other stuff.

11. Review Question In the passing position the pelvis drops slightly on the non-weight bearing side. This motion is called: A)Pelvic rotation B)Pelvic list C)Knee flexion D)Hip hula-hula E)The Twist

12. Pelvic List Pelvic list keeps the center of gravity from rising as much when the body passes over the weight-bearing leg, keeping the center of gravity on a flatter path of action. CG Stride Passing Position Stride CG Walking is more efficient with pelvic list. Path of Action of CG without List With Pelvic List Walking Forward B) Pelvic list

13. Review Question In normal walking, the side-to-side and up-down motion shown here is for the: A)Leg B)Arm C)Center of gravity D)Heel of the foot E)Hand Slow Fast Side-to-Side Up & Down Walking Forward Figure 8 Loop

14. 8-Loop & U-Loop C) Center of Gravity The center of gravity shifts up & down and also side-to-side. CG makes a Figure-8 loop when walking slow Makes a U-shape loop when walking fast. Slow Fast Side-to-Side Up & Down Walking Forward Figure 8 Loop

15. Joints & Levers

16. Toy Story (1995) Pixar’s Toy Story, directed by John Lasseter, was the first full-length feature film using computer animation. Tin Toy (1988, Pixar), also directed by Lasseter, won an Oscar in 1988 for Animated Short Film.

17. Tin Toy (1988) http://www.youtube.com/watch?v=vNZtl5SZvbM

18. The Polar Express (2004) The Polar Express was first full-length feature film made entirely with motion-capture animation. http://www.youtube.com/watch?v=2g-FRSq7x_o

19. “Uncanny Valley” Paradoxically, as computer generated characters get more realistic they start to be creepy. Realism  Appeal  Emily Project Polar Express Shrek 1 Beowulf Toy Story Tin Toy http://www.youtube.com/ watch?v=GBgURIUQ700

20. “Realism Tightrope” The uncanny valley occurs when some elements are more realistic than others. Our human instincts warn us something is wrong. Realistic Image  Appeal   Realistic Motion Completely Natural Tolerable Repulsive Robot Zombie Tolerable

21. Articulated Figures In computer animation characters are articulated figures, like marionette puppets. The challenge for animators is to move all the elements (arms, legs, hands, etc.) believably from frame to frame.

22. Joints Revolute Joint Prismatic Joint (Slider) Two kinds of joints: Revolute (rotation) and Prismatic (extension/contraction). Nearly all joints in animals are revolute joints

23. Axis of Rotation Rotation occurs around a line called the axis of rotation. The axel is the axis of rotation for a set of wheels.

24. Revolute Joints Revolute joints may have a single axis of rotation, like hinge joints and pivot joints, or a variable axis, such as the ball and socket joint. Elbow Shoulder Forearm

25. Forward Kinetics With forward kinetics (FK) the animator has to specify the axis of rotation and the angle of rotation for each joint on a moving limb. Lift the arm by a shoulder rotation Move forearm by an elbow rotation

26. Forward Kinetics Forward kinetics (FK) is a tedious process for the animator and it is difficult to maintain certain constraints, such as the planted foot in a walk.

27. Inverse Kinetics With inverse kinetics (IK) the animator positions the end effector, such as the hand, and the computer calculates the required joint rotations.

28. Inverse Kinetics Rotations calculated by the computer using IK are not always natural poses performed by a person. Furthermore, the timing may not be correct. Ball & Socket Hinge x x Raising hand into “High Five” pose Awkward IK Pose Elbow Wrist Shoulder

29. Understanding Rotation Just like any other type of motion, rotation is governed by Newton’s laws: Law of Inertia Law of Acceleration Action-Reaction Principle Let’s see how inertia, force, reaction, etc. appear in the context of rotational motion. Sir Isaac Newton

30. Mass is a measure of inertia for linear motion. Rotational inertia is similar concept for rotation. Inertia M m Gold brick Normal brick Difficult to move Easy to move x x Wood Bat Plastic Pee-wee Bat Difficult to Rotate Easy to Rotate

31. Rotational Inertia Rotational inertia depends on: Total mass of the object How the mass is distributed The farther the object’s mass is from the axis of rotation, the larger the rotational inertia.

32. Demo: Inertia Sticks Two metal pipes of the same mass Rotate Lead weights Easy to Rotate Hard to Rotate Axis of Rotation

33. Human Rotational Inertia In which pose does the dancer have a larger rotational inertia? Axis of Rotation A B A)Pose A B)Pose B C)Same for A & B since mass is unchanged.

34. Human Rotational Inertia Axis of Rotation A B B) Pose B Pose B has larger rotational inertia since the leg is extended, putting mass further from the axis of rotation.

35. Demo: Long Legs Long legs have greater rotational inertia than short legs so long legged animals have a slow walking stride.

36. Drag of Articulated Limbs Fast Swing Slow Swing Slow Fast The greater rotational inertia of longer limbs results in “drag”, just like with hair and fabrics.

37. Demo: Drop the Stick Two meter sticks stand upright against a wall; one has a hunk of clay on the end. Which stick will swing down and hit the floor first? The one without the hunk of clay. Why? Clay increases rotational inertia, which slows the rotation. Axis of Rotation

38. Demo: Drop the Stick Axis of Rotation X CG Another way to understand why the weighted stick takes longer to fall is that it’s center of gravity is higher. The higher it is, the longer it takes for an object to fall to the ground. Longer stick tips over more slowly

39. Tripping and Falling Axis of Rotation X CG If small child trips, he hits the ground more quickly than an adult. Can view this two ways: *Child has small rotational inertia. *Child’s center of gravity is initially closer to the ground.

40. Demo: Hammer Balance B A Axis of Rotation In which case is the hammer easier to balance on your finger? A)Case A B)Case B C)The same for A & B

41. Demo: Hammer Balance B) Case B In Case B the rotation is slower and thus easier to balance. In case B the rotational inertia is greater because most of the mass is far from the axis of rotation (at your fingertip). B A X CG

42. Tightrope Walkers The Great Blondin Is First to Walk Across Niagara Falls (June 30, 1859) Tightrope walkers carry a long pole to increase their rotational inertia, which slows their rotation when they’re off balance.

43. When a force causes a rotation, we identify this as a torque. Torque depends on Magnitude of Force Lever Arm (Torque) = (Force) x (Lever Arm) Torque

44. Lever Arm Lever arm is the perpendicular distance from axis of rotation to the direction of the force.

45. Opening or Closing a Door For a door the hinge is the axis of rotation. For maximum lever arm (and maximum torque), push perpendicular to the door at the edge opposite from the hinges. Door Hinge

46. Pirouettes A pirouette is typically done en dehors (moving leg starts at the front or the side and moves towards the back). A ballet turn done on one leg, starting with one or both legs in plié and rising onto demi-pointe (usually for men) or pointe (usually for women). http://www.youtube.com/watch?v=694S8oNXRZM

47. Torque for a Pirouette The farther the distance between the feet, the greater the lever arm so the greater the torque for creating the rotation. Push on Floor Reaction Force Lever Arm Feet apart (Easy) Feet together (Harder)

48. Fouetté (Whipped) Turns Done properly, the dancer returns to the same spot at the end of the turn. A turn executed with a quick thrust of the moving leg as it passes in front of or behind the supporting leg. http://www.youtube.com/watch?v=TV-N0QWyeac

49. Torque for Fouetté Turns Push on Floor Reaction Force Lever Arm Lower heel to the floor Push off while swinging right leg Lift heel and return to point The torque first creates a rotation of the arm & leg, then whole body rotates together

50. Fantasia (1940) The Dance of the Hours from Disney’s Fantasia is the most famous ballet scene in animation. http://www.youtube.com/watch?v=0pbQdtkbCcQ

51. Tipping and Torques Slowing out as an object tips over is due to the torque created by the force of gravity. X Lever Arm Gravity Force As the tipping angle increases, the lever arm increases so the torque (and acceleration) increase as well.

52. Slowing In and Slowing Out X If brick is not moving… …then it slows out as it tips over X If brick is moving upward… …then it slows in as it tips upward The lever arm changes with angle so the timing of this slowing in or slowing out has a lot of texture. Lever Arm

53. Horizontal Support This character’s center of gravity is not over her base of support. She does not tip over backwards (counter- clockwise rotation) since the wall exerts a torque in the clockwise direction, balancing the torque due to the gravity force. Wall force Lever Arm Gravity Lever arm Line of Gravity X

54. Mechanical Lever Lever converts an effort force into a load force by ratio of distances acting. Push down with a small effort force over a large distance Lift a large load weight over a small distance Axis of rotation goes through the fulcrum point. Fulcrum

55. First Class Levers Fulcrum Effort Arm Load Arm Lift a heavy load using small effort by having a long effort arm and/or short load arm. First Class Lever: Fulcrum is located in between the input force (effort) and output force (load).

56. Efficiency vs. Speed Effort Load Fulcrum Effort Load Fulcrum Efficient but slow Inefficient but fast

57. Examples of First Class Levers Crowbar Scissors Trebuchet Effort Load Fulcrum Crowbar and scissors are efficient (big load force) but slow (long effort distance). Trebuchet inefficient (big effort force) but fast (long load distance).

58. Second Class Levers Lift a heavy load using small effort by having a long effort arm and/or short load arm. Second Class Lever: Load is located in between the effort force and the fulcrum. Effort Arm Load Arm Fulcrum

59. Examples of Second Class Levers Wheel Barrow Effort Load Fulcrum Hole Punch Second class levers are always efficient and slow.

60. Third Class Levers Third Class Lever: Effort force is located in between the load and the fulcrum. Effort Arm Load Arm Second class levers are always inefficient but fast (since load arm is longer than effort arm).

61. Examples of Third Class Levers Effort Load Fulcrum Broom Jaw

62. Human Arm as a Lever Biceps muscle exerts effort force close to your elbow (fulcrum) to raise your forearm (load). This is what type of lever? A)First class B)Second class C)Third class

63. Human Arm as a Lever Biceps is a third class lever so a large effort force acts over a small distance to move a small load over a large distance. Triceps is also a third class lever, which pulls the arm in the opposite direction. Because muscles can only contract, they’re almost always found in pairs, like biceps/triceps. Effort Load

64. Human Foot as a Lever Effort Load Fulcrum To lift the body on the toes, the gastrocnemius (one of the strongest muscles in the body) contracts, lifting the heel upward. This is an example of a second class lever. Raising heel, as in walking.

65. Weight Shift Effort Load Fulcrum Weight shift forward shortens the load arm, reducing the required effort to lift the heel. Effort Load Fulcrum Line of Gravity

66. Human Neck as a Lever Load Fulcrum In general, the levers in animals’ bodies sacrifice efficiency for speed and to keep a compact body form. The neck muscles are the body’s only first class lever This lever is not efficient since the effort arm is shorter than the load arm. Effort

67. Action/Reaction for Torques For every action force there is an equal and opposite reaction force. Similarly, the action and reaction torques, caused by these forces, are equal. Accelerations from these torques depend on objects’ rotational inertia. If the action torque creates a clockwise rotation, the reaction creates a counter- clockwise rotation (and vice versa).

68. Action/Reaction for Torques Weightlifter exerts an action torque on the weights, rotating them counter-clockwise. The weights exert a clockwise reaction torque, pulling the weightlifter forward. Action Reaction

69. Fouetté Turns, Analyzed 1 2 3 4 5 6 The torque from pushing off gives angular momentum to the right arm and leg, which rotate freely from #1 to #4. Then the right arm and leg are made to rotate back in the opposite direction. By action/reaction, the torso recoils and rotates in the original direction. 1 2 3 4 5 6

70. Anchors Aweigh (1945) The musical Anchors Aweigh has a famous scene in which Gene Kelley dances with Jerry the Mouse. The scene climaxes with a series of fouetté turns. http://www.youtube.com/watch?v=xRMGRpDCW6k

71. Next Lecture Waves Part I Homework 9 (Reverse Video Reference) Due this Wednesday Homework 10 (Character Animation) Due Wed., Nov. 3 rd (In two weeks) Please turn off and return the clickers!