Video Analysis of Path of Action
In this assignment you will again use the Tracker software to analyze the path of action of a moving object from video reference. Specifically, you'll analyze yourself doing a running jump into the air. Note that if you prefer not to do the jumping yourself you still have to appear in the video, even if it's just to wave at the camera. The reason for this is so that I know that you didn't find the video somewhere on the internet instead of recording it yourself.
First, shoot some reference of yourself doing a running jump. Jump as high as you can (safely) since that will give you the maximum "hang time" in the air, which will improve the quality of your analysis results.
Position your camera far enough away so that you're in frame the entire time that you're in the air and stage the jump to be in profile. Keep the camera steady; if you don't have a tripod then sit the camera on a level surface. Shoot at least 5 takes, even if they are more or less the same.
Import your video reference into the Tracker software, which was introduced in the previous homework assignment.
In the "Tracks" menu select "New -> Point Mass"; a Track Control window should appear. Toggle the "Set Trail Length" button (near center of video window) to mark all points. Optional: Right click on the video to zoom in or out.
For the take that you want to analyze, go to the first frame in your clip where you leave the ground. Hold down the shift key to change the cursor into cross-hairs, then click on the center of your waistline or beltline, which is approximately the location of your center of gravity. The program will mark that position and advance one frame.
Continue holding down the shift and marking your position until after you've jumped and landed back on the ground. Due to motion blur it may be difficult to locate the exact center of your waistline but just do your best to estimate the center of the blur.
Click on the "Plots" button in the upper-right corner and select the 2 plot option. You should now have two plots showing your horizontal (x) and vertical (y) positions versus time. Select and drag the bar separating the plots from the data tables and pull the bar down to expand the plots window.
In the "Edit" menu select "Copy Image -> Frame" to copy the whole window to the clipboard. Open your favorite graphics program, such as PhotoShop, paste the image, then save it to a file. Upload that image to your blog into a post called "Video Analysis of Path of Action".
Finally, you will export a version of the video that includes the tracking points. Here are the instructions for doing that:
1. Using the blue slider at the bottom of the video, find the frame number where your jump begins (frame number is in red on the left of the slider). Then find the frame number where it ends. Write those down.
2. Click on the "Clip Settings" icon (blue film strip icon on the upper toolbar).
3. Change the start frame and end frame to the frame numbers you found in step 1 above.
4. Click on "Set trail length" (small circles icon in the upper toolbar) and choose "All steps"
5. From the File menu choose "Export -> Video clip..." then choose "View: Frame", and then 'Save as" to save your video.
6. If step 5 fails then go to "Preferences" in the Edit menu and change your Video Engine to Quicktime. Repeat step 5.
Please put both your original reference video (with all the jumps) and this second video of one jump with tracking points in your blog posting.
Here are some good examples from past semesters:
If you have problems completing any part of the assignment then be sure to post as much as you're able to do for partial credit.
* Video clip has you in it, preferably doing the running and jumping. Record at least five running jumps.
* On one of the jumps you track the center of your body while you're in the air.
* Show plots for both horizontal (x) position versus time and vertical (y) position versus time.
* Graph of horizontal position versus time is roughly a straight line.
* Graph of vertical position versus time is roughly a parabolic arc.
* Post your screen shot in a blog entry entitled "Video Analysis of Path of Action".
* In the same post include your original reference clip of your five jumps.
* Also post a recorded movie showing your path of action for at least one jump.
30 points (if late, 15 points)
Have a question? Go here.