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Upcoming Deadlines

Pick up a clicker, find the right channel, and enter Student ID. Upcoming Deadlines. First Term Paper The Laws of Physics in an Animation Universe Due Today! (at 8AM) 100 points (50 points if late) Eighth homework (Reverse Video Reference) Due Thursday, Oct. 27 (Next week)

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Upcoming Deadlines

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  1. Pick up a clicker, find the right channel, and enter Student ID Upcoming Deadlines First Term Paper The Laws of Physics in an Animation Universe Due Today! (at 8AM) 100 points (50 points if late) Eighth homework (Reverse Video Reference) Due Thursday, Oct. 27 (Next week) 20 points (10 points if late) For full schedule, visit course website: ArtPhysics123.pbworks.com

  2. Homework #8 Reverse video reference of walking  Normally, animators shoot video and use it as reference for their work. In this assignment, you will do the reverse. Specifically, you will watch each of three animation clips and shoot video in which you recreate them as accurately as possible.

  3. Homework #8 • Watch each of the three video clips on the assignment page • Film yourself acting out each scene, each in a separate clip. Reproduce the motion of the character as accurately as possible - you will be graded on how well you do this. Don’t just quickly act it out. Study each clip carefully to capture all of the motion details. Pay attention to staging, camera angle, camera moves (if any), etc. • Post all three videos in a blog entry entitled “Reverse Video Reference of Walking”

  4. Homework #8 Assignment is due by 8AM on Thursday, Oct. 27th 20 points (10 points if late)

  5. Extra Credit Opportunities * Attend the Animation Show of Shows - Friday (tomorrow), 7:30 at the Morris Daley Aud. There will be 10 films shown and out of 5 of the films, the directors will be there. Pls see Lauren B for attendance credit. * Attend any event at the NY-SF International Children’s Film Festival (October 21-23) Present proof of your attendance (receipt, photos, etc.) for 10 points of extra credit. * Attend any event at the San Francisco International Animation Festival (November 10-13). Present proof of your attendance (receipt, photos, etc.) for 10 points of extra credit.

  6. Review Question In this classic contrapposto pose, the weight of the body is primarily on which leg? B) Left Leg A) Right Leg

  7. Hips and Shoulders A) Right Leg 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)

  8. Weight Shift in Animation Rex Grignon, head of character animation at Dreamworks, says that not having weight shift is one of them most common errors seen in the work of student animators. Even when the lower body is out of frame, as in this medium shot, a good animator will think about what the lower body is doing because that’s reflected in the whole pose.

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

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

  11. Action &Reaction

  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 • Today we look at the Action-Reaction Principle, also known as Newton’s Third Law. Sir Isaac Newton

  13. Action-Reaction Principle For every action force there is an equal reaction force in the opposite direction. Reaction Action Action Reaction

  14. Action and Reaction Common expression for the principle is, To every action there’s an equal and opposite reaction. What’s an “action”? A force exerted by one object on second object. What’s a “reaction”? A force exerted by second object back on the first object that is causing the action. How can reaction be “equal” and “opposite”? Equal in magnitude but opposite in direction.

  15. Action-Reaction Pairs Action-reaction always occurs in pairs. Reaction: Jawexerts forceon fist Action: Manexerts force on rock Action: Fist exerts force on jaw Reaction: Rockexerts forceon man Action: (Thing A) exerts a force on (Thing B).Reaction: (Thing B) exerts a force on (Thing A).

  16. Law of Acceleration (Reminder) Object A has less mass (lighter) than Object B. Push each object with the same force. Object A Force Force Accelerations Object B By Law of Acceleration, Object A accelerates more than the (heavier) Object B.

  17. Class Demo: Mutual Attraction Mr. B has more mass (weighs more) than Mr. A What happens when: • Mr. A pulls, Mr. B holds. • Mr. A holds, Mr. B pulls. • Mr. A & Mr. B both pull. Mr. A Put them on skateboards to minimize the effect of friction force. Mr. B

  18. Class Demo: Mutual Attraction (cont.) If only Mr. A pulls on Mr. B then Mr. B accelerates. Reaction force of equal magnitude so Mr. A also moves. Who moves faster? Mr. A, Mr. B, or the same? Mr. B Reaction Action Mr. A Mr. A has less mass than Mr. B Accelerations Mr. A goes faster (greater acceleration) since his mass is less.

  19. Mutual Attraction Summary If A pulls B then both accelerate in response to equal forces.By Law of Acceleration, Object A, having less mass, will accelerate more than the heavier Object B. Object A Object B Reaction Action Accelerations

  20. Class Demo: Mutual Attraction (cont.) When both persons pull then there are two action forces and two reaction forces. If both pull with same force, how much greater is the acceleration than when only one pulls? Mr. B Reaction A Action A Mr. A Action B Twice the force, twice the acceleration Reaction B Accelerations

  21. Class Demo: Mutual Attraction (cont.) We replace Mr. B with a solid wall and Mr. A pulls on the wall (that’s the action force) . Due to the enormous mass of the building, the wall does not move. Wall exerts a reaction force, which pulls Mr. A towards the wall. Mr. A Reaction Action Acceleration

  22. Class Demo: Mutual Repulsion Similar demonstration is to have Mr. A and Mr. B push away instead of pull together. Same results; if Mr. A pushes and Mr. B holds then both move apart. Action Mr. B holds Mr. Apushes Reaction SmallAcceleration LargeAcceleration

  23. Mutual Repulsion Summary If A pushes B then both accelerate by equal forces.By Law of Acceleration, Object A, having less mass, will accelerate more than the heavier Object B. Object A Object B Action Reaction Accelerations

  24. Class Demo: Mutual Repulsion (cont.) If we replace Mr. B with a solid wall then Mr. A pushes on the wall (that’s the action force) but due to the enormous mass of the building, the wall does not move. Wall exerts a reaction force, pushing Mr. A away from the wall. Mr. A Action Reaction Acceleration

  25. Wile E. Coyote & Action/Reaction “Beep Beep” (1952) Action/Reaction is often violated for comic effect. http://www.youtube.com/watch?v=csIIFGFr1wU http://www.youtube.com/watch?v=vobhUvhO8N0 “Gee Whiz-z-z-z” (1956)

  26. Kung-Fu Panda End credits of KFP play with the 3rd law, but consistently.Strong characters have mass; the weak ones are light. Weak Strong

  27. Action/Reaction in KFP http://www.youtube.com/watch?v=YGg6QiNOZ28 Watch the reaction for each character as they strike the inanimate punching bag.

  28. Fight Scenes Fight scenes are more realistic when reaction punches and kicks show the reaction force Reaction: Jawexerts forceon fist Action: Fist exerts force on jaw

  29. Spiderman 3 (2007) Most elements of this fight scene do not have realistic reaction forces to match the actions.

  30. From Russia with Love (1963) This early James Bond film has a very brutal, realistic fight scene. http://www.youtube.com/watch?v=Ea7JxAvzUMg A recent Bond film (Casino Royale, 2006) starts with a similarly realistic fight scene in a bathroom.

  31. Kung fu Hustle (2004) In a comedy it’s best to make a fight scene less realistic, which makes it funny. http://www.youtube.com/watch?v=glsUlacDN7Q

  32. Recoil Action/Reaction also explains recoil, such as from a gun.The action force that accelerates the bullet results in areaction force in opposite direction, recoiling the gun. Heavy cannon Fast cannonball Recoil Speed = (Bullet/Gun Weight Ratio) x (Bullet Speed) Example: If the cannon weighs 100 times more than the cannon ball then cannon’s recoil speed is 100 times less than cannon ball’s speed.

  33. Recoil from a Gun High recoil speed is cause by either: * Large Bullet/Gun Weight Ratio * High Bullet Speed Shooting an elephant gun http://www.youtube.com/watch?v=MlFlXMHaSVQ http://www.youtube.com/watch?v=bpFDHO-tqUY

  34. Predator (1987)

  35. Eraser (1996) http://www.youtube.com/watch?v=aHoIMBXKSos

  36. Recoil & Wile E. Coyote http://www.youtube.com/watch?v=Wxm9EdVFxk8 Unexpected recoil is another common gag in animated cartoons. Guided Muscle (1955) http://www.youtube.com/watch?v=7H6Pwzdw7oQ

  37. Force, Time, and Impulse When any force causes a change in velocity, the more time that the force can act, the greater the change in the velocity. Pushing apart, these guys only exert forces on each other as long as their hands are together.

  38. Crouching for a Jump Crouching is useful when jumping because it extends the time of contact for pushing off the ground. Push Height X X Apex Crouch Take-off

  39. Pushing an Object The man pushes on the rock but he is also pushing on the ground. Action: Manexerts force on rock Reaction: Rockexerts forceon man Reaction: Groundexerts forceon man Action: Manexerts force on ground Man moves forward when reaction from the ground is more than from the rock.

  40. Shaolin Soccer (2001) Extreme kung-fu action appears in Shaolin Soccer. http://www.youtube.com/watch?v=bREfcVPssiE Think about the forces exert by the woman’s arms (pushing) and feet (holding her in place).

  41. IMPORTANT!!! Action force & reaction force NEVER cancel because they act on different objects! Repeat this to yourself over and over again

  42. Reaction Action Balance of Forces? Miss A pushes the cart (action); cart pushes back on her (reaction). Do these forces cancel? No, the two forces act on different objects. Force on Miss A is to the left; how can she move forward (to the right)? Miss A pushes back on the ground with her feet (action) reaction of ground on her is to the right. What if ground had zero friction (like ice)? Then Miss A can’t move forward. Miss A Action Reaction Action- Reaction Pairs

  43. Balance of Forces? Mr. B also pushes from the inside of cart but obviously he can’t move the cart alone. In terms of Newton’s laws, why not? Because the total force exerted by Mr. B on the cart is zero. What other force does Mr. B exert on the cart besides his hands? His butt pushes back on the cart and the floor of the cart pushes back on him. The two action forces balance each other and the two reaction forces balance each other. Mr. B Reaction Action Action Reaction Action- Reaction Pairs

  44. Wile E., Propelled http://www.youtube.com/watch?v=rv7PWDjjjqk From “Ready, Set, Zoom” Using an outboard motor in a tub for propulsion, as doneby Wile E. Coyote, would actually work, True or False?

  45. Internal Propulsion False. Internal propulsion is not possible because the impulse gained from one reaction is lost due to another internal action. Propeller pushes water Water pushes propeller Tub pushes water Water pushes Tub Action/Reaction Pairs

  46. Wile E., Propelled II http://www.youtube.com/watch?v=wkMOfeXItUU From “Scrambled Arches” Using a strong fan and a big sail for propulsion, as doneby Wile E. Coyote, would actually work, True or False?

  47. Internal Propulsion False. Internal propulsion is not possible because the impulse gained from one reaction is lost due to another internal action. Air pushes propeller Propeller pushes air This would work! Sail pushes air Air pushes sail Action/Reaction Pairs

  48. Wall-E Fire, Propelled http://www.youtube.com/watch?v=2lkffSsImXc Using a fire-extinguisher for propulsion, as used by Wall-E, would actually work, True or False?

  49. Class Demo: Extinguisher Rocket http://www.youtube.com/watch?v=9F_VjHZATbY Using a fire-extinguisher for rocket-like propulsion.

  50. Next LectureJumping Homework #8 (Reverse Video Reference of Walking)Due next Thursday Please turn off and return the clickers!

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