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Pick up a clicker, find the right channel, and enter Student ID. Upcoming Deadlines. Eighth Homework (Reverse Video Reference) Due Thursday, March 22 nd (This week) 20 points (10 points if late) Spring Break - March 26th to March 30th Ninth Homework (Stop-motion Character Animation) - PowerPoint PPT Presentation

Transcript of Upcoming Deadlines

  • Upcoming DeadlinesEighth Homework (Reverse Video Reference)Due Thursday, March 22nd (This week)20 points (10 points if late)

    Spring Break - March 26th to March 30th

    Ninth Homework (Stop-motion Character Animation)Due Tuesday, April 10th (In three weeks)20 points (10 points if late)

    For full schedule, visit course website:ArtPhysics123.pbworks.comPick up a clicker, find the right channel, and enter Student ID

  • Homework Assignment #8Normally animators shoot video and use it as reference for their work. In this assignment, you'll do the reverse. Specifically, for four different animation clips youll shoot video of yourself in which you recreate those clips as accurately as possible.Go to Homework Assignment 8 on the course website to find the animation clips youll recreate:https://artphysics123.pbworks.com/Homework-8

  • Homework Assignment #8Upload your four clips to your blog in an entry entitled Reverse Video Reference of Walking."This assignment is due by 8am on Thursday, March 22nd (this week).20 points (if late, 10 points).

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

  • Survey CommentsLike: Demos; Videos; Interesting & organized lectures; Clickers; Grading system & extra credit

    Dislike: Term papers; Tracker; Quizzes

    Suggest: Change 8am due-time; more clicker questions; more clicker time; clicker points?; fewer term papers; free beer

  • Survey QuestionThe amount of time that youre given to answer the clicker questions is: too short; would like more time.about the right amount of time.too long; dont need so much time.

  • 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:

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

  • Swinging Arms in a JumpWhile 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.

  • Spin or Tumble?Rotation around two of these axes is spinning. In this pose, the axis of rotation that tumbles is:Twisting axis (Head-to-toe axis;Turn left-to-right)B) Somersault axis (Side-to-side axis;Turn front-to-back)C) Cartwheel axis (Front-to-back axis;Turn head-to-feet)ABC

  • Spin or Tumble?B) Somersault axis (Side-to-side axis;Turn front-to-back)

    BRotating along this axis typically results in irregular tumbling.

    Spinning is possible but requires more control than along the other two axes.

  • Tennis Racket TheoremWhen an object turns about its long or its short axis, it tends to spin uniformly.

    When an object turns about its middle axis, it tends to tumble.SPINSPIN

  • WalksPart I

  • Characters in Motion - WalksWalking is a great example for studying character motion because it has all the basic elements of mechanics.

  • Walks with PersonalityFrom the basic walk its 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 Landreths Oscar-winning short, Ryan, about the troubled life of Ryan Larkin.http://www.nfb.ca/film/Walkinghttp://www.nfb.ca/film/ryan/

  • Stride & Passing PositionOne foot in the airFeet on the groundStridePassing PositionConcentrate on these two key poses, the stride and the passing position.

  • Squash & StretchPassing positionSquashStretchThese are the transition poses between the stride and the passing position.StrideStride

  • Animating a Walk CycleIs animating a walk cycle just a matter of getting the right sequence of poses?No, its more complicated. Lets see why

  • Video AnalysisTo help us analyze a walk, lets look at some video analysis using the Tracker software.

  • Video Analysis

  • Video Analysis

  • Head PositionStridePassingHeight

  • Richard Williams WalkWilliams puts the up position just after the passing position, which happens if the heel rises in a quick walk.

  • Preston Blairs WalkPreston Blair makes the passing position the tallest point in his basic walk cycle.Richard Williams also does this in many cases.PassingStrideStridePassingStrideStrideBut in walks with attitude, he mixes it up.

  • Rules vs. ToolsThere is enormous variety in walks and each has unique timing and spacing.

    As Glenn Vilppu says,No rules, just tools!

    Physics is a tool that helps animators create believable walks.

  • Step, Stride, GaitStride =2 StepsGait is the timing of movement in walking, running, etc.

  • Cadence of a Walking GaitStrobe 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 groundRight FootLeft FootIn the air60%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.At around 6-7 feet per second (4-5 m.p.h.) the gait pattern transitions into a run.

    WalkStride lengthStride rateSpeedSlow walk3 feet2/3 stride per second2 feet per sec. (1 1/3 m.p.h.)Fast walk4 feet1 stride per second4 feet per sec. (2 2/3 m.p.h.)

  • Period of a Simple PendulumPeriod of this pendulum is about one second per oscillationTime 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).XX* 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 GaitShort 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. XCGXCG

  • Drag of Articulated LimbsFast SwingSlow SwingSlowFastDrag (inertia) is seen with articulated limbs

  • Drag in Character EffectsFast SwingSlow SwingSlowFastDrag (inertia) is also seen in character effects, such as hair and clothes

  • Timing of the WalkTiming is almost even but there is some slowing in and slowing out as the center of gravity rises and falls.Slowing InSlowing OutXCGXCGXCG

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

  • Rolling Egg TimingThe timing of the motion due rising and falling center of gravity (CG) is like that of a rolling egg.Slowing InSlowing OutXCGXCGXCG

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

  • Weight Shift in WalksUp and down motion in a walk causes weight changes for the character.

  • Weight on the GroundAt which position do you exert the least weight on the ground?StrideSquashPassing PositionStretchSame weight at all timesStrideStrideStrideP.P.P.P.SquashSquashStretchStretch

  • Force Plate ExperimentsC) Passing Position

    Can measure weight shift during walk cycle using force plates.Body WeightStretchPassingPositionPassingPositionSquashStretchStrideSquash

  • Weight Shift Normal Walks

  • Weight Shift Normal WalksThe 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 WalksIn the middle of the passing position the weight on the planted leg dips to a minimum.This weight is actually 20%-40% less than the person's weight when standing stationary on one foot.

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

  • Weight Shift Normal WalksThe 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.Im going to kill Garcia for this!

  • CounteractionRichard Williams calls this effect of varying weight the counteraction.Williams writes, When the character goes up the drapery or hair or soft bits go down.Lose WeightLose WeightGain Weight

  • Normal, Slow, and Fast GaitsNotice the differ