Pick up a clicker, find the right channel, and enter Student ID Upcoming Deadlines Fifth Homework (Video Analysis of a Jump) Due Wednesday, Feb. 24th (This week) 15 points (10 points if late) Sixth Homework (Stop-motion Animation) Due Wednesday, March 3rd (Next week) 20 points (if late, 10 points) Bonus prize of 20 extra points to top three. For full schedule, visit course website: ArtPhysics123.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 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.
Homework Assignment #5 Use Tracker to analyze the motion of yourself doing a running jump. Shoot reference with at least 5 takes. Track the center of your body (center of torso at about the beltline) in the air. Upload original video, screen shot with graphs, video with tracking*. This assignment is due by 8am on Wednesday, Feb. 24th (this week). 15 points (10 points if late) *May be tricky
Homework Assignment #5 Straight Line Parabolic Path of Action Parabolic Curve
Homework Assignment #6 In this assignment you will create a stop-motion animation of a falling object. It can be a simple as a ball bounce cycle or (preferably) something more interesting, like a flour sack or a water balloon. Because you will have to pose your object at different heights, you'll either need to suspend it from a string or have the motion occur on the ground with the camera positioned directly overhead.
Homework Assignment #6 http://www.youtube.com/watch?v=uQXXmGUwn4E
Homework Assignment #6 If you have a webcam, an easy way to film a stop-motion animation is to use SAM Animation (http://www.samanimation.com/). It's free software that runs on both Macs and PCs; it was developed at Tufts University as part of a National Science Foundation project for teaching using animation. The software is designed so that it can be used by even elementary school children so you shouldn't have much trouble figuring it out.
Homework Assignment #6 An alternative is to shot a sequence of photos (not a movie!) with your digital camera and to combine the photos into a movie file or an animated GIF. This is as simple as using cut/paste if you have Quicktime Pro; if not then you could use any one of a number of freeware or trialware video editing programs (the software that came with your digital camera may have this capability).
Homework Assignment #6 You can also create an animated GIF in Photoshop. To do that, place each photo in a different layer, use the Animation tool (in Window menu) to combine them, finally use "Save for Web & Devices" to save the animation as a GIF (there are many tutorials on-line explaining how to do this).
Homework Assignment #6 Your animation should be composed of at least a dozen different images, though you may want to use the same photo in one or more frames to get the timing right. Try to make the motion as physically correct as possible; because it is difficult to go back and make corrections in stop motion animation you'll want to plan out your object's positioning ahead of time.
Homework Assignment #6 Your assignment will be scored on both the believability of the object's motion and on the creativity of your animation. You can adjust the timing by putting the same image on more than one frame (e.g., "shooting on twos") or deleting some frames. Don't hesitate to simply reshoot your animation; often that's easier than trying to make corrections.
Homework Assignment #6 While I encourage you to help each other out, for this assignment each person needs to create their own animation. Finally, describe in a brief paragraph how you created your animation. Post your animation clip to your blog in an entry entitled "Stop Motion Animation of Falling.“ Due by 8am on Wednesday, March 3rd. 20 points (if late, 10 points) The top three animation clips in the class will receive a bonus of 20 extra points.
Survey Question • The lecture slides are posted on the course website as both PowerPoint and PDF files. • How many times have you looked at these slides? • Never • Once, maybe twice • A few times
Review Question In reality, it is impossible to travel upside-down, as Wile E. Coyote does in this scene. True or False? “Beep 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.
Jackass 2 (2006) http://www.youtube.com/watch?v=36fD7KSUjkw
Why Things Move So far we’ve only looked at how things move (slowing in/out, path of action, arcs, etc.). Now it’s time to look at why things move, that is, what causes action. The short answer is forces. To understand why things move the way they do, you need to consider the forces at play.
Newton’s Laws of Forces • Newton established three basic laws to explain how motion is caused by forces: • Law of Inertia • Law of Acceleration • Action-Reaction Principle • Disney and other early animators rediscovered these laws of forces in their studies of motion. Sir Isaac Newton
Follow-Through When a character stops, it doesn’t suddenly freeze. Some parts of the character stop abruptly while others, such as arms, long hair, clothing, etc., continue moving for a few frames. In animation, this is known as follow-through. In physics, we know it as Newton’s Law of Inertia.
Motion, with & without Forces An object moves with constant, uniform motion until acted on by a force. No force An asteroid floats in space with a constant speed unless gravity deflects its motion. FORCE
Balance of Forces Rarely are there no forces but often forces are balanced so they “cancel” each other out. Important: Balanced forces does not mean that there’s no motion! Floor Tension Gravity Gravity Floor Gravity
Law of Inertia Newton’s Law of Inertia says: An object moves with constant, uniform motion until acted on by an unbalanced force. Floor Gravity The bowling ball moves with constant speed* *In reality, there is a small unbalanced force, friction, that does slow the ball’s speed.
Home Demo: Riding the Bus When a moving bus halts, you continue moving forward.
Shoot ‘Em Up (2007) If the crash occurs at 35 miles per hour then the hero flies off at a speed of about 2 feet per frame.
Shoot ‘Em Up (2007) Frame 438 Stuntman flies out the window at about 10 m.p.h. Frame 439 Frame 440 Frame 441 This is a bit slow but at a realistic speed the audience wouldn’t see the action.
Shoot ‘Em Up (2007) Frame 459 Stuntman flies into the van at about 5 m.p.h. Frame 460 Frame 461 Frame 462 Noticeably much too slow but the sequence is outrageous anyway, so it works.
The League of Extraordinary Gentlemen (2003) http://www.youtube.com/watch?v=n8SDdkKSqns In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet.
The League of Extraordinary Gentlemen (2003) In this scene, Sean Connery jumps out the side of a speeding car and lands on his feet. In reality, he would: • Roll forward from where he lands, in the direction of the moving car. • Roll backwards from where he lands. • Land just as he does in the movie; this was actually done by a stuntman.
Jumping out of a Car A) Roll forward You are moving at the same speed as the car when you jump out so you will roll forward. Your path car You’ll start losing speed after you hit the ground so, relative to the car, you’ll fall behind as the car continues speeding along.
Centrifugal Force Revisited The centrifugal force you experience on taking a sharp curve is nothing more than inertia keeping you moving forward in a straight line. It feels as if you’re pulled to the outside bank of the curve. Your path
Law of Inertia (cont.) Newton’s Law of Inertia also says: An object at rest (not moving) remains at rest until acted on by an unbalanced force. A stationary bowling ball remains stationary until some unbalanced force comes along. Floor Gravity This is nothing more than motion at constant speed but with speed equal to zero.
Home Demo: Riding the Bus (cont.) If the bus starts moving again, you remain stationary, seemingly thrown backwards.
Frame of Reference Bus Moves Background As seen by observer on the street As seen by observer sitting in the bus
Jackass (2002) http://www.youtube.com/watch?v=V-dFVdhgSsc
Class Demo: Tablecloth Pull Due to the vase’s inertia it remains at rest since almost no force acts on the vase if one pulls quickly and straight. Yank quickly
Inertia & Drag An object won’t move until a force acts on it so long hair trails behind as head turns. Although this is due to the hair’s inertia, in animation it’s usually called drag. An object at rest remains at rest until acted on by a force.
Inertia & Drag (cont.) Hair remains in motion even after the head stops turning, which is follow-through due to inertia. Object in motion remains in motion until acted on by an unbalanced force.
Drag in Arcs and Waves Animation drag is very noticeable when something like hair or cloth moves in an arc or in a wave-like motion.
Class Demo: Hula Skirt The motion of a hula skirt is an excellent example of animation “drag.” Also notice how the skirt moves outward as it turns due to centrifugal force.
Flour Sack Exercises The sack drop and sack pantomime are common animation exercises. A flour sack is a good proxy for learning character animation since it shows follow-through and drag. Dancing withthe Sacks
Importance of Follow-through & Drag “Now we could use Follow-through on the fleshy parts to give us the solidity and dimension, we could drag the parts to give the added feeling of weight and reality. It all added up to more life in the scene. The magic was beginning to appear.” From The Illusion of Life - Disney Animation Notice the subtle follow-through in the hands, skirt, and pant legs for the last drawing of the Moving Hold. By Ham Luske
Leaf/Paper Drop Test Animate a leaf (or piece of paper) drifting slowly to the ground. That was not a good leaf drop Let’s see some good ones by Gloria Cho and Katie Corna.
Leaf Drop Test http://www.youtube.com/watch?v=mbMo4HFJC1Y
Paper Drop Test http://www.youtube.com/watch?v=vKf-vIDSIik
Air Resistance Air resistance is a force created when an object moves through air. Air Resistance • Depends on: • Size (area) of the object • Speed of the object • Larger the size or speed, larger the resistance. Gravity
Demo: Hand out the Window Experience the force of air resistance by holding your hand out a car window. Resistance increases as speed increases. Resistance increases as area increases.
Demo: Falling in a Vacuum Feather falls slowly due to air resistance force. If we remove the air (create a vacuum) then feather and coin fall with same acceleration.
Home Demo: Drop the Sheet A flat sheet of paper falls slowly because of air resistance. What happens if we place it on top of a book, blocking the air from reaching it? Air Resistance Weight Book and sheet fall together