Upcoming Deadlines Pick up a clicker find the

Upcoming Deadlines Pick up a clicker, find the right channel, and enter Student ID Fifth Homework (Video Analysis of a Jump) Due Wednesday, Feb. 24 th (Next week) 15 points (10 points if late) Sixth Homework (Stop-motion Animation) Due Wednesday, March 3 rd (In two weeks) 20 points (if late, 10 points) Bonus prize of 20 extra points to top three. For full schedule, visit course website: Art. Physics 123. pbworks. com

Activating your Clicker * Turn on your clicker. * Enter the channel number or letter for joining this class. Hit Enter/Send key. * Clicker should read AP 123 S 258 * 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 Opportunity Go 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 Opportunity Attend the Game Developer’s Conference in San Francisco, on Saturday, March 13 th Student registration is $75 (ouch) Turn in your receipt for 10 points of extra credit. For info: www. gdconf. com

Homework Assignment #5 In this assignment you’ll 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 #5 Original Video Reference

Homework Assignment #5 Import 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 you’ve 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 #5 Straight Line Parabolic Path of Action Parabolic Curve

Homework Assignment #5 Finally, 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 #5 Video Reference with Tracking

Homework Assignment #5 Check 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 You. Tube or Vimeo. This assignment is due by 8 am on Wednesday, Feb. 24 th (week from today). 15 points (10 points if late)

Survey Question So far the pace of the class has been: A)Too fast B)A little fast C)About right D)A little slow E)Too slow

Review Question The 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 Drop Height D) Frames

Arcs in Animation

Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion of Life, Frank Thomas and Olie Johnston list a set of basic principles for animation. 1. 2. 3. 4. 5. Squash & Stretch Timing Anticipation Staging Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7. Slow In and Slow Out 8. Arcs 9. Exaggeration 10. Secondary Action 11. Appeal

Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion of Life, Frankdiscussed Thomas We have already and Olieseveral Johnston a setprinciples of basic oflist these principles animation. of for animation, specifically: 1. 2. 3. 4. 5. Squash & Stretch Timing Anticipation Staging Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7. Slow In and Slow Out 8. Arcs 9. Exaggeration 10. Secondary Action 11. Appeal

Disney’s Principles of Animation In their classic book, Disney Animation – The Illusion Thomas Todayof we. Life, will. Frank discuss arcs and Olieand Johnston list arelate set of to basic how they principles for animation. animated motion. 1. 2. 3. 4. 5. Squash & Stretch Timing Anticipation Staging Follow Through & Overlapping Action 6. Straight Ahead & Pose-to-Pose Action 7. Slow In and Slow Out 8. Arcs 9. Exaggeration 10. Secondary Action 11. Appeal

Arcs of Motion usually follows an arc, which may be simple, like a circle, or very complex and irregular.

Importance of Arcs Disney animation legends Frank Thomas and Olie Johnston write: One 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. Right Wrong

Circular Arcs Circular arcs are common since motion is often around a fixed pivot point, such as a joint.

Speed in Circular Motion Rotational Speed: Revolutions per second Tangential Speed: Total distance per second Same Rotational Speed Different Tangential Speeds

Throwing Arm Sling lengthens the arm at almost no cost in the weight. Doubling the speed quadruples the range! x 2 al ti en d ng ee Ta Sp The longer the throwing arm, the greater the tangential speed so the farther it can throw.

Timing on Circular Arcs A circular arc is a simple path of action but the timing may be complex and textured. in ow Uniform Slow Sl t ou In this golf swing the motion: • Slows out (accelerates) to hit the ball • Uniform after the hit • Slows in as the swing finishes follow-through

Non-Uniform Circular Motion Two common types of motion on circular arcs that have non-uniform timing and spacing are: Exponential Spacing Example: Tipping over Pendulum Spacing Example: Stride in walking

Tipping Over Tipping over is a common example of motion on a circular arc. Two ways to tip over: X Center tipped past point of contact X Center past an edge

Tipping Rotation A brick rotates about a point as it tips; that point is the center of a circular arc. X X Friction tends to keep the brick from sliding until it loses contact with the table.

Exponential Spacing Release 1 1 Constant acceleration (Odd Rule) 3 2 5 3 1 Release 7 4 2 3 Exponential Spacing 4 As the slope of the incline increases, the acceleration itself accelerates.

Rolling off a Tipping Point 1 2 3 4 5 6 7 Peak 8 Slowing out from a tipping point is very slow initially, but then accelerates rapidly.

Video Reference of Tipping Brick http: //www. youtube. com/watch? v=ot. YAYMZ 4 i. Gg

Anticipation & Exponential Spacing Texture of the timing as the brick tips over creates anticipation, which you want at the start of a scene Also notice motion blur near top of brick, which has large tangential speed.

Pendulum Spacing A pendulum’s path of action is also a circular arc but the spacing is very different from the exponential spacing of tipping over.

Spacing & Timing in Swinging A 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 Example http: //www. youtube. com/watch? v=xuo. Jd. NGxff. U

Motion Graph for Pendulum The motion graph (angle vs. frame) shows that the timing is mostly textured (curves the most) at the apexes. SL O aga W, in SLOW, again Angle #7 #1 FA ST FAST #4 Ball goes fastest around the bottom but the speed is almost constant. SLOW Frame

Uniform Rotation in Perspective The timing for uniform rotation has texture when seen in perspective. Half orbit Quarter orbit Rotation from key #1 to #5 in background takes twice as long as from #6 to #8 in foreground.

Swinging in Perspective Visually 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=s. LNqt. U-g. YPc

Demo: Don’t Flinch Pendulum swings back and forth yet it doesn’t hit your face.

Bowling Ball Pendulum http: //www. youtube. com/watch? v=UNs. D 15 Gj. WWE Click This video clip lets you experience what it’s like to do this demo.

Spirals A spiral is just a circular arc with a radius that’s either increasing (spiral out) or decreasing (spiral in). Concept art from Pirates of the Caribbean 3

Rotational Speed in Spirals If the radius decreases without pulling the object inward then the rotational speed increases (due to shrinking radius) but the tangential speed stays constant. Spacings along the curve stay constant. Spiral In

Demo: Interrupted Pendulum An “interrupt” bar changes the radius of the arc for a pendulum. Tangential 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. Bar

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. Spacings along the curve get bigger and bigger. Spiral In

Demo: Skater’s Spin Slow Rotation FAST Rotation Exert 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. Spacings along the curve get shorter yet it still spins faster and faster. Spiral In Coin Vortex

Rotation in a Spirals In 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? 1 2 XX 3 X No! The brick does 4 not fall this way. X

Video Reference of Tipping Brick http: //www. youtube. com/watch? v=ot. YAYMZ 4 i. Gg

Forces on the Tipping Brick The table pushes on the brick upward and towards the right. Gravity pulls downward Center of the brick shifts down and towards the right. X X If no table…

Pushing Off by the Table X Once it loses contact with the table, only the force of gravity accelerates the brick. X X The table pushes away on the brick, which causes the brick to move away from the table as it falls.

Centrifugal Force Insect inside a can rotating in a circle When we move on an arc, it seems to us as if there is an outward force, pushing us away from the center of the circle. Physicists call this apparent force the centrifugal force. What we see What the insect feels

Class Demo: Bucket Overhead I will put a bucket full of water over my head without getting wet. How? By rotating it fast enough. The water stays in the bucked as if pressed into it by a centrifugal force. You experience centrifugal force on taking a sharp turn Centrifugal Force

Wile E. Coyote & Loop-D-Loop Watch carefully as Wile E. Coyote travels in a circle around a natural arch bridge. From “Beep” (1952) http: //www. youtube. com/watch? v=p 4 Yxd. Xw 9 evc

Wile E. Coyote & Loop-D-Loop In reality, it is impossible to travel upside-down, as Wile E. Coyote does in this scene. True or False? “Beep” (1952)

Wile E. Coyote & Loop-D-Loop False. If his speed is high enough then he stays in contact with the arch, just like the water in the spinning bucket.

Demo: Loop-the-Loop If the speed of the ball is large then not only does it stay on the track, the ball even pushes outward and against the rail. Release Velocity

Demo: Loop-the-Loop Ball could even circle a loop with a gap, if the speed was just right so gravity was equal to the centrifugal force. Release Velocity GAP

Simulated Gravity Centrifugal force could be used to simulate gravity in a space station. With the appropriate rotational speed a person on the outer rim would feel as if they stood on the surface of Earth. Scientifically accurate in the movie 2001: A Space Odyssey (1968) Rotation

2001: A Space Odyssey (1968)

Simple Spinning A falling brick may turn by. Arbitrary simple spinning around its center. 1 1 2 In simple spinning, the angle rotates at a constant rate. A brick tipped 45º as it loses contact with the table will fall spinning about 30º every two frames. 3 3 5 4 7

Tumbling A falling brick may Arbitrary also turn by a more complicated tumbling motion. 1 1 2 There is no simple way to describe tumbling. However, the brick’s center still follows the same parabolic path of action. 3 3 5 4 7

Tennis Racket Theorem SPIN When an object turns about its middle axis, it may tumble. SPIN TUMBLE When an object turns about its long or its short axis, it tends to spin.

Irregular Objects SP IN SPIN TUMBLE SPIN M U T E L B SPIN

Spin or Tumble? Rotation around two of these axes is spinning. The axis of rotation that tumbles is: A) Head-to-toe axis B) Side-to-side axis C) Front-to-back axis A B C

Spin or Tumble? B) Side-to-side axis Rotating along this axis typically results in irregular tumbling. Spinning is possible but requires more control than along the other two axes. B

Rolling & Slipping 1 2 3 4 5 6 7 ROLLING Rolling ball turns one revolution when it travels a distance equal to three times its diameter (actually 3. 1416 diameter) 1 2 3 4 5 SLIPPING Slipping and rolling are both uniform in spacing and rotation.

Next Lecture Creating Action By Wednesday of next week: Complete the 5 th homework (Video analysis of Path of Action) Please return the clickers!