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Transcript of Upcoming Deadlines
Upcoming DeadlinesFifth Homework (Video Analysis of a Jump)Due Wednesday, Feb. 24th (Next week)15 points (10 points if late)
Sixth Homework (Stop-motion Animation)Due Wednesday, March 3rd (In two weeks)20 points (if late, 10 points)Bonus prize of 20 extra points to top three.
For full schedule, visit course website:ArtPhysics123.pbworks.comPick up a clicker, find the right channel, and enter Student ID
Activating your Clicker* Turn on your clicker.* Enter the channel number or letter for joining this class. Hit Enter/Send key.* Clicker should read AP123S258* 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.
Extra Credit OpportunityGo to any event at Cinequest Film Festival in downtown San Jose.Turn in proof of attendance (receipt, photos, etc.) for 5 points of extra credit.
Extra Credit OpportunityStudent registration is $75 (ouch)
Turn in your receipt for 10 points of extra credit.
For info: www.gdconf.comAttend the Game Developers Conference in San Francisco, on Saturday, March 13th
Homework Assignment #5In this assignment youll again use Tracker software to analyze the motion of a moving object from video reference.First, shoot some reference of yourself doing a running jump. Position your camera so that you're in frame the entire time that you're in the air.Stage the jump to be in profile. Shoot at least 5 takes, even if they are more or less the same.
Homework Assignment #5Original Video Reference
Homework Assignment #5Import your video reference into the Tracker software (as in previous homework).Track the center of your waistline or beltline, which is approximately the location of your center of gravity. Marking your position from the time you leave the ground until youve landed.After tracking your motion, upload the screen image from Tracker to your blog into a post called "Video analysis of path of action".
Homework Assignment #5ParabolicPath of ActionStraight LineParabolic Curve
Homework Assignment #5Finally, rewind your video to the first frame of your jump and from the "File" menu select "Record -> Quicktime Movie".
Hit the play button and allow the clip to play until the end of your jump. Next, in the "Capturing Quicktime MOV" window click "Save As" to save the recording.
Homework Assignment #5Video Reference with Tracking
Homework Assignment #5Check that your saved Quicktime movie has the track showing the path of action then put both clips (original and with tracking) in your blog post using YouTube or Vimeo.
This assignment is due by 8am on Wednesday, Feb. 24th (week from today).
15 points (10 points if late)
Survey QuestionSo far the pace of the class has been:
Too fastA little fastAbout rightA little slowToo slow
Review QuestionThe motion graph for a ball drop, going from the apex until the ball just touches the ground, looks like:A)B)C)D)
Motion Graph of a Ball DropFramesHeightD)
Arcs in Animation
Disneys Principles of AnimationIn their classic book, Disney Animation The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation.
Disneys Principles of AnimationIn their classic book, Disney Animation The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation.We have already discussed several of these principles of animation, specifically:
Disneys Principles of AnimationIn their classic book, Disney Animation The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation.Today we will discuss arcs and how they relate to animated motion.
Arcs of MotionMotion usually follows an arc, which may be simple, like a circle, or very complex and irregular.
Importance of ArcsOne of the major problems for the inbetweeners is that it is much more difficult to make a drawing on an arc.Drawings made as straight inbetweens completely kill the essence of the action.Disney animation legends Frank Thomas and Olie Johnston write:WrongRight
Circular ArcsCircular arcs are common since motion is often around a fixed pivot point, such as a joint.
Speed in Circular MotionRotational Speed: Revolutions per secondTangential Speed: Total distance per secondSame Rotational SpeedDifferent Tangential Speeds
Throwing ArmTangentialSpeedThe longer the throwing arm, the greater the tangential speed so the farther it can throw.Sling lengthens the arm at almost no cost in the weight.Doubling the speed quadruples the range!x2
Timing on Circular ArcsIn this golf swing the motion: Slows out (accelerates) to hit the ball Uniform after the hit Slows in as the swing finishes follow-throughA circular arc is a simple path of action but the timing may be complex and textured.Slow outUniformSlow in
Non-Uniform Circular MotionTwo common types of motion on circular arcs that have non-uniform timing and spacing are:Exponential SpacingPendulum SpacingExample: Tipping overExample: Stride in walking
Tipping OverTipping over is a common example of motion on a circular arc. Two ways to tip over:XXCenter tipped past point of contactCenter past an edge
Tipping RotationA brick rotates about a point as it tips; that point is the center of a circular arc.XXFriction tends to keep the brick from sliding until it loses contact with the table. XX
As the slope of the incline increases, the acceleration itself accelerates.Exponential Spacing1371234Constant acceleration (Odd Rule)Release51234ReleaseExponential Spacing
Slowing out from a tipping point is very slow initially, but then accelerates rapidly.Rolling off a Tipping Point12345678Peak
Video Reference of Tipping Brickhttp://www.youtube.com/watch?v=otYAYMZ4iGg
Anticipation & Exponential SpacingTexture of the timing as the brick tips over creates anticipation, which you want at the start of a sceneAlso notice motion blur near top of brick, which has large tangential speed.
Pendulum SpacingA pendulums path of action is also a circular arc but the spacing is very different from the exponential spacing of tipping over.
Spacing & Timing in SwingingA pendulum will slow in and out as it swings back and forth, the same as a ball rolling in a half-pipe.Most of the texture in the timing is at the endpoints; the timing is even in the center.
Pencil Test Examplehttp://www.youtube.com/watch?v=xuoJdNGxffU
Motion Graph for PendulumThe motion graph (angle vs. frame) shows that the timing is mostly textured (curves the most) at the apexes.FrameAngle#1#4#7FASTFASTSLOWSLOWSLOW,againSLOW,againBall goes fastest around the bottom but the speed is almost constant.
Uniform Rotation in PerspectiveThe timing for uniform rotation has texture when seen in perspective.Rotation from key #1 to #5 in background takes twice as long as from #6 to #8 in foreground.
Swinging in PerspectiveVisually the timing has even more texture when the swing occurs in perspective.
Who Framed Roger Rabbit? (1988)The opening sequence in Who Framed Roger Rabbit? makes great use of the textured timing of arcs in perspective.Animation by Richard Williams
Who Framed Roger Rabbit? (1988)http://www.youtube.com/watch?v=sLNqtU-gYPc
Demo: Dont FlinchPendulum swings back and forth yet it doesnt hit your face.
Bowling Ball PendulumThis video clip lets you experience what its like to do this demo.Clickhttp://www.youtube.com/watch?v=UNsD15GjWWE
SpiralsA spiral is just a circular arc with a radius thats either increasing (spiral out) or decreasing (spiral in).Concept art from Pirates of the Caribbean 3
Rotational Speed in SpiralsIf the radius decreases without pulling the object inward then the rotational speed increases (due to shrinking radius) but the tangential speed stays constant.Spiral InSpacings along the curve stay constant.
Demo: Interrupted PendulumTangential speed does not increase due to the pendulum whipping around the interrupt bar.
Energy is not increased by the interrupt bar so ball swings back to the same spot.BarAn interrupt bar changes the radius of the arc for a pendulum.
Rotation in Spirals (cont.)If the radius decreases by pulling the object inward then the rotational speed increases due to shrinking radius and due to an increase in the tangential speed.Spiral InSpacings along the curve get bigger and bigger.
Demo: Skaters SpinSlowRotationFASTRotationExert a force to pull hand weights toward my body, causing a big increase in rotational and tangential speeds
Rotation in Spirals (cont.)If the tangential speed decreases (say by friction) but inward force constant then the rotational speed still increases.Spiral InSpacings along the curve get shorteryet it still spins faster and faster.Coin Vortex
Rotation in a SpiralsIn summary, typically as an object rotates in a spiral, the rotation speed increases as the radius decreases. So as radius goes down, the r.p.m.s go up.
However the spacings may get longer, or shorter, or stay constant!
How Does the Brick Fall?Does the brick rotate and then fall down the side of the table?XXNo! The brick does not fall this way.XX4321
Video Reference of Tipping Brickhttp://www.youtube.com/watch?v=otYAYMZ4iGg
Forces on the Tipping BrickXXThe table pushes on the brick upward and towards the right.