Upcoming Deadlines

Fourth Homework (Tracker Video Analysis)Due Thursday, Sept. 15th (Next week)15 points (10 points if late)

Fifth Homework (Analysis of Path of Action)Due Thursday, Sept. 29th 15 points (10 points if late)

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

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

Homework Assignment #4

One of the most useful tools for an animator is a movie camera for shooting reference.

Reference is not for rotoscoping (tracing images from a film) but to study the motion.We can also use video analysis tools to help us see the patterns of motion in a scene that we’ve filmed.

Tracker Video Analysis Software

For this assignment you will use Tracker,a software tool for video analysis.

To download Tracker, visit: http://www.cabrillo.edu/~dbrown/tracker/

Tracker is a free program created by Doug Brown, a physicist at Cabrillo College.

Importing Video into Tracker

Run the Tracker program on your computer and import your video clip of a falling object.You may need to convert your clip into a format that Tracker can import (either MOV or AVI), if it's not already in that format. If you have trouble using your clip from Homework 3 then you may shoot new reference.

Tracking an Object in Tracker

In the "Tracks" menu select "New -> Point Mass";

a Track Control window should appear.

Press the second button in the Track Control window and select the "Full Trails" option. Go to the first frame in your clip that you want to analyze, hold down the shift key to change the cursor into cross-hairs, then click on the center of your object. The program will mark that position and advance one frame.

Tracking an Object (cont.)

Continue holding down the shift and marking the position of the object until it hits the ground (which should be after 15 to 20 frames).  

Due to motion blur the object will "stretch" as it falls and it may be difficult to locate the exact center but just do your best to estimate the center of the blur.

Plotting the Position Data

Click on the "Plots" button in the upper-right corner and select the 2 plot option.

You now have two plots showing the horizontal (x) and vertical (y) positions of the object versus time. Select and drag the bar separating the plots from the data tables and pull the bar down to expand the plots window.  

Tracking the Ball Drop

HorizontalMotion

VerticalMotion

Posting your Plots

In the "Edit" menu select "Copy Image -> Frame" to copy the whole window to the clipboard.

Open your favorite graphics program, such as Paint or PhotoShop, paste the image, then save it to a file. Finally, upload that image to your blog into a post called “Tracker video analysis of falling". Visit this course’s blog to see examples.

This assignment is due by 8am on Thursday, September 15th (next week).

15 points (if late, 10 points)

Assignment Checklist* Video clip is from previous homework assignment (or similar if you reshoot your reference).

* Track the falling object from about the time of release until it hits the ground. You may continue tracking bounces (optional).

* Show plots for both horizontal (x) position versus time and vertical (y) position versus time.

* Graph of vertical position versus time is roughly a parabolic arc.

* Post your screen shot in a blog entry entitled "Tracker video analysis of falling"

Activating your Clicker

* Turn on your clicker.* Enter the channel number or letter for

joining this class. Hit Enter/Send key.* Clicker should read AP123KF11* 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.

Survey Question

Have you looked at your classmate’s blogs?

A) Not yetB) Looked at a coupleC) Looked at many of them

Note: You score 1 point of credit for answering survey questions, regardless of your answer.

Paths ofAction

Wile E. Coyote’s Path of Action

In reality, Wile E Coyote would fall straight back down instead of curving in an arc. True or False?

“Beep Beep” (1952)

In this scene Wile E. Coyote (on rocket skates) is launched straight up the side of a vertical cliff. His path of action then curves into a parabolic arc.

Wile E. Coyote’s Path of Action (2)

In reality, he would fall in a downward arc similar to his upward path of action. True or False?

“Beep Beep” (1952)

Wile E. Coyote travels in a roughly parabolic arc up to the apex, then stops and falls straight downward.

Bending the Laws of Physics

Wile E. Coyote takes a beating but we don’t feel that it’s animal cruelty because the laws of physics are bent, reminding us that he’s in a cartoon universe.

Making the action more realistic would change our emotional reaction to the scene.

“Attack of the Clones” Review

http://www.youtube.com/watch?v=9QThD0r3hZg

Staging

Staging is one of the principles of animation.

Motion is often more interesting when staged to occur with some perspective.“Spend half your time planning your scene and the other half animating.” Ollie Johnston

Brick Drop with Perspective

http://www.youtube.com/watch?v=gJBDow84MLw

Arcs in Perspective

Parabolic arcs look different in perspective but the spacings follow all the same rules as for arcs in profile.

Half Arc in Perspective

VP

HL

1

3

Use the “Fourth Down at Half Time” rule to help locate points

Falling towards foreground

Perspective tends to straighten this arc

Half Arc in Perspective

VP

HL

1

3

Use the “Fourth Down at Half Time” rule to help locate points

Falling towards background

Perspective tends to increase curvature for this arc

Parabolic Arc in Perspective

VP

HL

Ball starts and ends on the ground.

Maximum height (ball at midpoint)

Parabolic Arc in Perspective (cont.)

VP

HL

1

3

Add points to the curve by using “Fourth Down at Half Time” rule.

Apex in Perspective

Apex needs to be above the half-way point between take-off and landing, which is harder to judge with perspective.

Apex of a Jump

Let’s check if the apex of this jump is correct.

http://www.youtube.com/watch?v=e2Hyqz3XHV0

Apex of a Jump

Correct

Apex

Hancock (2008)Parabolic arcs seen in perspective are interesting because the timing has texture as motion goes from foreground to background.

But the timing in this scene from Hancock is wrong. Can you tell why?

http://www.youtube.com/watch?v=VseQOjm9xPU

Next LectureTracking and Motion Graphs

Due next Thursday:Homework #4

(Analyzing Video)

Please turn off and return the clickers!