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Upcoming Deadlines Pick up a clicker, find the right channel, and enter Student ID Eighth homework Reverse Video Reference of Walking Due Thursday, Oct. 27 (this week) 20 points (10 points if late) For full schedule, visit course website: ArtPhysics123.pbworks.com

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.

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”

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

Survey Question Up to now, roughly how many hours per week do you spend this class (outside of attending class): A) An hour or less per week B) About two hours per week C) Four hours, on average D) Six hours a week, more or less E) Well over 6 hours per week

Review Question Mr. A pushes way from Mr. B while Mr. B just holds his hand rigidly in place. Which of them has the largest acceleration? Mr. B holds • Mr. A • Mr. B • They have the same acceleration Mr. Apushes

Review Question Mr. A has the larger acceleration. 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

Wile E. Coyote, Propelled • Which of these devices would actually work to propel Wile E. Coyote? • Outboard motor in a tub of water. • Big fan blowing a large sail. • Both would work. • Neither would work. A) B)

Back of the tub acts like the sail. Internal Propulsion 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

Jumps

Jumping Jumping is a basic character animation exercise that incorporates many of the basic elements found in drop tests for inanimate objects. By Carlos Nunez By Danielle Domurat http://www.youtube.com/watch?v=XWheRtQkC9o http://www.youtube.com/watch?v=jwerYsdE9Xs

Timing the Jump The simplest part of a jump is the time in the air and how it is related to the height of the jump. Jump Time X Jump Height X Apex X = Center of Gravity Crouch Take-off

Jump Time & Height The same table we saw for the ball drop gives the jump time (from take-off to apex) and jump height. The formula to compute this table is: (Distance in inches) = (Number of Frames) x (Number of Frames) x (1/3 inch)

Hang time = 2x(Jump time) Jump Time Example For a jump time of 8 frames, the jump height is 21 inches 8 frames 8 frames X 21 inches X X Apex Landing Take-off X = Center of Gravity

Crouching Tiger, Hidden Dragon (2000) http://www.youtube.com/watch?v=xxCvv3bDyvw Characters stay in the air an unrealistically long time, even considering the impressive height of their jumps.

Timing the Push You can time the push (from crouch to take-off) using a simple formula Jump Time Push Time X Jump Height X Push Height X Apex X = Center of Gravity Crouch Take-off

Jump Magnification Timing of the push depends on the jump magnification. Jump Height Push Height Jump Magnification = Jump Magnification = 8 Jump Magnification = 2

Formula for Timing the Push Jump Time Jump Magnification Push Time = Can use this formula to check the timing of the push depending on the timing of the jump.

Timing the Push Example 8 frames 8 frames X = Center of Gravity 4 frames Apex X 21 inches X X 10 ½ inches X Jump magnification = 2so push time is half aslong as the jump time. Landing Crouch Take-off

Planning a Jump Animators can plan out a realistic jump by these steps: • Pick the desired jump time or jump height. • Use the table to find the jump height given the jump time (or vice versa). • Pick the desired push height for the crouch • Determine the push time from the jump magnification.

A Big Jump A character jumps 16 feet into the air. From the table, that’s a jump time of 24 frames (take-off to apex). The push height is 16 inches; what is the push time? Jump Time Jump Magnification Push Time = Apex Jump Height = 16 feet Push Height = 16 inches Jump Time = 24 frames • Two frames • Four frames • Six frames • Eight frames • Twelve frames

A Big Jump • Two frames Jump Time Jump Magnification Push Time = Apex Jump magnification is 12 (=16 feet/16 inches) Push time is (24 frames)/12 = 2 frames Jump Height = 16 feet Push Height = 16 inches Jump Time = 24 frames

Push Factor Can calculate jump magnification with this: Jump Magnification = (Push Factor) x (Push Height in Feet) Push Factor = 36 / (Push Time in Frames)2

The Incredible Hulk The Incredible Hulk is big, let’s say 10 feet tall. Say his push height when he jumps is 3 feet. If you animate 2 frames from crouch to take-off, how high does he jump? For a push time of 2 frames the push factor = 9 so the jump multiplier is (Jump multiplier) = (9) x (3) = 27 (Push Factor) x (Push Height) Jumps about 8x his height He jumps 81 feet into the air since his push height of 3 feet gets magnified by a factor of 27 (the jump multiplier).

The Hulk (2003) The enormous jumps by the Hulk look fake because, for such huge jump magnifications, the push time would be less than one frame. http://www.youtube.com/watch?v=5JsDylEPNh0

Boundin’ (2003) Big jump magnifications and jump times give a feeling of lightness and happiness in a cartoon. http://www.youtube.com/watch?v=CDtiZImH0qI

Timing the Landing If the crouch on landing is similar to the crouch when pushing off then the landing has similar timing to the take-off. If the crouch on landing is shorter then the timing of the landing is shorter; if the crouch is longer, the timing is longer.

Forces when Jumping The three main forces on a person jumping are: • Gravity (Downward) • Support of the floor (Upward) • Frictional force of the floor (Horizontal) Only these forces can accelerate the person. Gravity is constant but the force exerted by the floor can increase in reaction to the action of the person exerting a force on the floor.

Jumping Action/Reaction Jumping is done by pushing downward on the ground (action) so the ground pushes upward on you (reaction). How high you jump depends on the force and on the distance over which you apply that force. Reaction Action Can only push while in contact with the ground so squatting helps by increasing distance.

Average Push Force You can determine the average force exerted when jumping as: (Jump Force) = (Jumper’s Weight) x (Jump Magnification) Remember that Jump Height Push Height Jump Magnification = Jump Force (Action)

The Incredible Hulk If The Hulk has a push height of 3 feet and he makes a huge jump, rising a height of 300 feet, how much force does he push with? Jump magnification is 100 so the push force is 100 times his weight. The Hulk is twice as tall as a normal person so his weight is at least 8 times larger (probably closer to 10-12 times larger). So if The Hulk weighs 2000 lbs, he’s pushing off with 200,000 lbs of force (200 tons).

Action/Reaction Jumping Forward To jump upward and also forward, the action force (pushing downward with your legs) needs to also be pushing towards your back so that reaction force of the floor is upward and forward. Reaction Action Jumping forward at a 45° requires almost 50% more pushing force to reach the same vertical height.

Forces when Landing If the timing of the landing is similar to the timing of the take-off then the forces on landing are similar to the forces on take off. If the landing has quicker timing then the forces are proportionally larger on the landing. If the landing has slower timing than the take-off then the landing forces are smaller. Reaction Action

Hancock (2008) One of the few things in this movie that’s physically accurate is that the force exerted on the ground is just as extreme on the take-off as it is on the landing. Landing Take-off

Overlapping Action Overlapping action is all the secondary motions that occur in addition to the primary motion. In this example the primary motion is the jump itself.Motion of the arms and head are active secondary motions, created by the character, while the drag of the clothing, hair, etc. are passive secondary motions.

Secondary Action Secondary actions are a part of acting. They are the extra actions that actors (and animators) use to convey personality or mood. Click http://www.synchrolux.com/?p=273 For example, in this scene Hogarth is playing with the telephone cord to convey that he is bored and knows exactly what his mother is going to tell him to do.

Timing of Overlapping Actions Overlapping actions may or may not have timing that matches that of the primary motion. Passive secondary motion, like follow-through and drag, is more likely to be synchronized with the primary motion but sometimes active secondary motion is also synchronized, in support of the primary motion.

Swinging Arms in a Jump The natural motion when jumping is to swing the arms upward as fast as possible while the feet are in contact with the ground. Swinging the arms raises the center of gravity and also increases the downward action force pushing off the ground.

Swinging Arms in a Jump The height of a jump is significantly lower (almost 30% lower) if you don’t swing your arms during the take-off portion of a jump. However, if you swing your arms after leaving the floor, then the height of the jump is much lower.

Home Demo: Jumping & Arm Swing First, jump normally, that is, swing your arms upward while feet are still on the ground. Now try swinging your arms upward after you leave the ground; you’ll notice a big difference.

Home Demo: Somersault Now let’s try using the arms in a backwards somersault Tuck increases rotation speed Motion of the arms is also useful here for control of the rotation.

Arm Motion while in the Air While in the air, moving your arms can shift the center of gravity and change rotation but it cannot change time in the air or the distance. Long jumpers move their arms to control the rotation of their body so as to land feet first. http://www.youtube.com/watch?v=P5Sg_kACPRM

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

Demo: Spin Up the Wheel Counter- Clockwise Rotation Zero Rotation Clockwise Rotation By pushing the bike wheel to turn it one way, the recoil causes me to rotate in the opposite direction.

Helicopter’s Tail When a helicopter’s blades start turning in one direction, by conservation of angular momentum the body would spin in the opposite direction. Blades Body To compensate, the small rotor in the tail exerts a force to keep the body from turning. If small rotor fails, helicopter spins out of control.

Demo: Mid-Air Twist Stand up and clear space around you. When I say “Jump!”, jump. In mid-air I’ll point left or right and I want you to try to turn so you land facing that direction. Jump! Turn Land How can you rotate in mid-air without pushing off of anything?

Demo: Mid-Air Twist As you turn your legs 90 degrees, your arms and torso rotate in the opposite direction. Sticking your arms out as you turn helps by increasing the rotational inertia of your upper body. A large rotation of your legs is exactly cancelled by a small rotation of your outspread arms and torso. Jump! Turn

Demo: Mid-Air Twist Your rotation stops as soon as you stop rotating your upper body but by that time you’ve landed with your feet turned to the side. Once on the ground you can push off on the ground to restore your arms and torso to a normal stance. Turn Land

Front Side 180 Jump! Turn Land The same principle is used in skateboarding tricks, such as a front side 180, in which a skater does a half turn in mid-air, turning upper and lower torso in opposite directions.

Demo: Drop the Cat Again www.abc.net.au/science

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