Upcoming Deadlines

First Term Paper The Laws of Physics in an Animation UniverseDue Wednesday, March 17th (This week)100 points (50 points if late)

Homework #8Reverse Video Reference of WalkingDue Wednesday, March 24th 20 points (10 points if late); 20 point bonus to top 5

For full schedule, visit course website:ArtPhysics123.pbworks.com

Pick up a clicker, find the right channel, and enter Student ID

Upcoming Furlough DatesThe Wednesday before Spring Break and

the Monday after Spring Break are both furlough days for this class.

Those dates may or may not be furlough days for your other classes.

Homework #8 is still due on Wed., March 24th (Wed. before Spring Break) even though class will not meet on that day.

Homework #9 (Stop-motion character animation) is due on Wed., April 7th (Wed. after Spring Break) and class will meet on that date.

Homework Assignment #8

Normally animators shoot video and use it as reference for their work.

In this assignment, you'll do the reverse. Specifically, for five different animation clips

you’ll shoot video of yourself in which you recreate those clips as accurately as possible.

Go to Homework Assignment 8 (Analysis of Walking) on the course website to find YouTube links to the five animation clips.

Homework Assignment #8Clip A

Clip B

Clip C

Clip D Clip E

Homework Assignment #8Film yourself acting out the scene in each of the five

animation clips, recording a separate clip of yourself for each one.

Reproduce the motion of the character in the animation as accurately as possible (you'll be graded on how well you do).

Don't just quickly act it out but rather study each animation clip carefully to capture all the details in the motion, including staging and camera angle.

The purpose of this exercise is to have you carefully observe the motion in each clip so that you will learn the complexity of different walks.

Homework Assignment #8Upload your five clips to your blog in an entry

entitled "Analysis of Walking." 

This assignment is due by 8am on Wednesday, March 24th

20 points (if late, 10 points).

For each of the five animation clips the best video clip will get an extra 20 points of credit.

Extra Credit Opportunity

See the Wayne Thiebaud exhibition at the San Jose Museum of Art.

During your visit, also catch the “Real and Hyperreal” exhibition.

Give me your ticket receipt for five points extra credit.

Two Kneeling Figures, 1966

James Doolin, Shopping Mall, 1973-77

San Jose Museum of Art

Hours: Tuesday – Sunday, 11am - 5pm Admission: $5.00 for studentsLocation: 110 South Market St.

You are here

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joining this class. Hit Enter/Send key.* Clicker should read AP123S258* Type in your student ID; hit

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Survey Question

You have about half (or more) of your term paper written.

True or False

The Incredible Hulk

The Hulk crouches down 2 feet and then makes a huge jump, rising a height of 200 feet.If his weight is 2000 lbs, with how much force did he push off?

A) 2000 lbsB) 4000 lbsC) 80,000 lbsD)100,000 lbsE) 200,000 lbs

The Incredible Hulk

Jump Magnification = 8

E) 200,000 lbs

Jump magnification is 100 so the push force is 100 times his weight. Since The Hulk weighs 2000 lbs, he’s pushing off with 200,000 lbs of force (200 tons).

Jump Magnification = Jump HeightPush Height

Swinging Arms in a JumpThe natural motion when jumping is to swing the arms. To jump as high as possible you should swing them upward:

A)While your feet are still touching the ground.B)Just after your feet leave the ground.C)Either way, since the forces on the arms and on the feet are not related.

Swinging Arms in a JumpA) While your feet are still

touching the ground.

Swinging the arms raises the center of gravity and also increases the downward action force pushing off the ground.

WalksPart I

Characters in Motion - Walks

Walking is a great example for studying character motion because it has all the basic elements of mechanics.

Walks with Personality

From the basic walk it’s possible to create many variations to express personality through acting.

Walking (1968)Ryan Larkin created an Oscar-nominated short of people walking, animated in a variety of styles.

This clip is from Chris Landreth’s Oscar-winning short, Ryan, about the troubled life of Ryan Larkin.

http://www.nfb.ca/film/Walking

http://www.nfb.ca/film/ryan/

Stepping ReflexStepping is an innate reflex can be triggered by holding an infant under the arms and allowing the feet to touch a flat surface. The infant will lift one foot after another in a stepping response, like walking.

From an evolutionary perspective, this reflex exists to prepare the newborn for voluntary walking.

Most babies take their first steps between 9 and 12 months and can walk well by 14 or 15 months.

Step, Stride, Gait

stride length step length

left foot

swing phase,left foot

right foot

stance phase,left foot

single-support double-support

one gait cycle

time

Stride =2 Steps

Gait is the timing of movement in walking, running, etc.

Time

Distance

Cadence of a Walking Gait

Strobe photo (5 flashes per second)

A normal walking gait ranges from a third to two-thirds of a second (8 to 16 frames) per step, with a half second (12 frames) per step being about average.

A full stride (both rightand left steps) is, on average, one second (24 frames) per cycle.

Parade march time is 120 beats per minute (one beat per step).

One stride (two steps)

Contact with the GroundEach foot is on the ground about 60% of the time.About a 20% of the time both feet touch the ground.

On the ground

Right Foot

Left FootIn the air

60%

60%

40%

40%

10%

10%

10%

10%

Time of dual contact decreases as walking speed increases.

Walking Slower or FasterGoing from a slow walk to a fast walk you increase both your stride length and your stride rate to increase your speed.

Walk Stride length

Stride rate Speed

Slow walk 3 feet 2/3 stride per second

2 feet per sec.(1 1/3 m.p.h.)

Fast walk 4 feet 1 stride per second

4 feet per sec.(2 2/3 m.p.h.)At around 6-7 feet per second (4-5

m.p.h.) the gait pattern transitions into a run.

Period of a Simple Pendulum

Period of this pendulum is about one second per oscillation

Time required for a full oscillation (one round trip) is called the period of oscillation.

Period of a simple pendulum depends only on its length (distance from the pivot to the mass).

Greater the length, the slower the oscillation.

Period of a Cylinder PendulumPeriod of a cylinder pendulum depends mostly* on its length (distance from the pivot to center of gravity).

X X

* Also depends on the radius; larger the radius, the slower the oscillation.

Greater the length, the longer the period for the swing (that is, the slower stride rate).

Leg swing is like this

Period of Walking Gait

Short legged characters have quicker gait than long legged ones.

During the stride, the passing leg swings at its natural period of oscillation.

Running GaitIn running, you bend your leg and raise your calf and foot to quicken gait by shortening the distance from the pivot (hip) to the center of gravity of the leg.

XCG

XCG

Period and LengthThe relationship between the period of oscillation and a pendulum’s length is given in this table.This is relation between time and distance comes from the “Fourth Down at Half Time” law.

Example: If the stride of a 6 foot man takes 1 second then the stride of a 150 ft giant (25 times taller than the man) takes _______ seconds.

five

Period Length

x 2 x 4

x 3 x 9

x 4 x 16

x 5 x 25

x 10 x 100

Outrunning a GiantIf a giant walks with a gait that matches his size, would you walk at a faster speed than the giant?No. For example, if the giant is 25 times your height then although each step takes 5 times longer, with each step he goes 25 times farther so he covers 5 times the distance in the same amount of time.

Jason and the Argonauts

Empire Strikes Back (1980)

http://www.youtube.com/watch?v=JhpS69eAXrU

Notice the timing of the giant walking tanks.

Stride & Passing Position

One foot in the air

Feet on the

ground

Stride Passing Position

Concentrate on these two key poses, the stride and the passing position.

Squash & Stretch

Passing position

Squash Stretch

These are the transition poses between the stride and the passing position.

StrideStride

Video Analysis

To help us analyze a walk, let’s look at some video analysis using the Tracker software.

Video Analysis

Video Analysis

Head Position

Stride

Passing

Heig

ht

Richard Williams’ Walk

Williams puts the “up” position just after the passing position, which happens if the heel rises in a quick walk.

Preston Blair’s Walk

Preston Blair makes the passing position the tallest point in his basic walk cycle.

Richard Williams also does this in many cases.

PassingStride Stride

PassingStride Stride

But in walks with attitude, he mixes it up.

Rules vs. Tools

There is enormous variety in walks so there are few solid rules to follow.

As Glenn Vilppu says,“No rules, just tools!”

Physics is a tool to help you create believable walks.

Timing of the Walk

Timing is almost even but there is some slowing in and slowing out as the center of gravity rises and falls.

Slowing In Slowing Out

XCGXCG XCG

Inverted PendulumIn the passing position the whole body swings up and down, as an inverted pendulum.

Rolling Egg Timing

The timing of the motion due rising and falling center of gravity (CG) is similar to that of a rolling egg.

Slowing In Slowing Out

XCGXCG XCG

Home Demo: Carrying WaterTo appreciate the “rolling egg” timing of a walk, carry a shallow tray of water and notice the rhythm of the sloshing.

Slowing In Slowing Out

XCGXCG XCG

Walking stiff legged, like Frankenstein, exaggerates the slowing in and out.

Weight Shift in Walks

First consider the up and down motion in a walk and what accelerations are created by the weight shift of the body.

Weight on the Ground

At which position do you exert the least weight on the ground?

A) StrideB) SquashC) Passing

PositionD)StretchE) Same weight

at all timesStride Stride StrideP.P.P.P.

Squash Squash

Stretch Stretch

Force Plate Experiments

C) Passing Position

Can measure weight shift during walk cycle using force plates.

Body Weight

Stretch

PassingPosition

PassingPosition

Squash Stretch

Stride

Squash

Weight Shift – Normal Walks

Weight Shift – Normal Walks

The weight on the back foot is peaks just as the heel of the front foot touches the ground.

Moments later, the weight on the front foot is peaked right as the back foot leaves the ground.

Andrew Harkins, Dreamworks animator

Weight Shift – Normal Walks

In the middle of the passing position the weight on the planted leg dips to a minimum.

This weight is actually 10%-20% less than the person's weight when standing stationary on one foot.

Weight Shift – Normal Walks

The reason that the weight decreases is that the body rises upward then downward during the passing position, swinging like an inverted pendulum. Due to the centripetal force required to move your body in a small arc during the passing position causes your weight to be lower. This effect is seen in overlapping actions, especially if a character has long hair or loose fitting clothes.

I’m going to kill Garcia for this!

“Counteraction”

Richard Williams calls this counteraction.“When the character goes up – the drapery or hair or soft bits go down.”

Normal, Slow, and Fast GaitsNotice the differences in the three walks yet the similarities among different persons.

Slow walk has less variation in the weight shift

Fast walk has more variation in the weight shift

Normal walk

Force Plate – Slow Walks

Force Plate – Fast Walks

Center of Weight during a StepThe center of weight travels from heel to toe as the torso travels over the planted foot, almost half the time located near the ball of the foot.

Heel Strike Squash

Passing Position

Stretch

Walking with a Limp

On the ground

In the air

With a limp, the painful leg is still on the ground 60% of the time but walking slowly reduces force spikes in the squash and stretch.

Quadruped Animal Walking

Walking for animals is very different than for humans, not so much because they walk on 4 legs but due to bone structure.

101 Dalmations (1961)The walking gaits of the dogs in this scene is modified to match that of their masters.

Walk cycles animated by Frank Thomas and Blaine Gibson

Click

http://www.youtube.com/watch?v=wpj9E3H4_Ag

AT-AT WalkersIndustrial Light & Magic (ILM) filmed the AT-ATs using stop-motion animation with models from 2 inches to 2 feet in height.

Walking mimics elephants

Star Wars Episode V: The Empire Strikes Back

Shoulder, Elbow, WristFront legs of mammals have the same joints but bones are of various lengths.

From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

Shoulder

Elbow

Wrist

Horse Human Dog Cat ???

Dog Legs

Notice the joints circled in this skeleton of a dog; on a human these would be:A) Elbows and KneesB) Elbows and AnklesC) Wrists and KneesD)Wrists and AnklesE) None of the above

B) Elbows and Ankles

Dog Legs

Tennis Shoes & Stripped Socks

From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

Chuck Jones presents a good way to remember animal anatomy: Tennis shoes & Stripped socks.

Knee

Ankle

Sole

Sole, Ankle, Knee

From Chuck Amuck: The Life and Times of an Animated Cartoonist By Chuck Jones

Knee

Ankle

Sole

Knee

Knee

Ankle

Ankle

Sole

Sole

HorseHuman Dog

What you think is the “knee” on the hind leg is actually the ankle.

Next LectureWalks, Part II

First Term PaperDue this Wednesday!

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