Scientific Motion Tracking with Blender

Motion tracking with a python csv export script. 11 Aug 2014

The following details a method for tracking the rotation and translation of a single object in 2D with Blender.

Requirements

Open Blender
Click the screen-layout dropdown on top
- Choose the “Motion Tracking” option
At the bottom of the largest screen area, select the open icon
- Browse to your video file
Select the “End” box at the bottom of the screen and change it to the number of frames in your video.
Using the timeline at the bottom of the screen, make sure that you are at frame #1
In the main tracking pane, hold down ctrl and click on the insect head. This adds a tracker.
With the new tracker selected, type “sy” to scale in the y-direction and “sx” to scale in the x-direction. Type “r” to rotate, and “g” to translate. Make sure the marker only covers the locust’s face.
On the right, expand the “tracking settings section and change Motion to “LocRot” and Match to “Keyframe”. Check “prepass” and “normalize”
With the tracker selected click the track forward button, or type control-t to track the marker through the entire footage.
- If the tracking stops partway through, manually move the tracker to the correct position and type control-t to continue. I found this not to be necessary in my case.

Download the export script from GitHub (Alternatively, you can run git clone https://gist.github.com/7b96bba85ed81aba864a.git in a terminal)
Change the editor type for the right-side area to “Text Editor”, by opening the menu on the lower-right of the right-hand-side pane.
Click the “Open” button on the bottom of the text editor to open the markers.py file downloaded above.
In the text editor change the line OUT_DIR = '/tmp' to refer to the directory where you want to save your output files. Do not include a trailing slash in your directory path.
Press the “Run Script” button at the bottom of the text editor. (you may need to scroll right in order to see it).

A .csv file with the following format will be generated in the output directory specified:

  <frame_number>,<position-x>,<position-y>,<corner1-x>,<corner1-y>,...,<corner4-x>,<corner4-y>