The Secret Tracking Strategies
of the Interrupting Cows

Who we are:

The Interrupting Cows are a tracking system created to capture leg motion.

How we do it:

The tracking is done by finding the brightly marked joints on a character, calculating the differences between the joints in proportion to the height, and then calculating the joint angles. A curve is then placed through the joints, with interpolation to help with smoothing.

What was attempted, but failed:

Between placing the markers and converting the images to the needed format, information was lost (lossy jpeg compression). This led to higher-than-expected difficulty levels in finding the markers.

What worked:

We used an animated figure as our data. We chose this data due to vision concerns. There is no unexpected noise in an animation, therefore making the determination of markers easier. We placed the markers by hand using Adobe Photoshop. The markers were placed on the ankles, knees, and hip joints, as well as the head (to determine height). We then wrote a program to locate these markers and their coordinates, as well as to calculate the lengths of the limbs and the height of the figure.
We use this information to calculate joint angles, and use the joint angles to create a motion curve in joint angle space. It deals with occlusions of markers by interpolating between the known coordinates.
We made several assumptions:


We were able to generate curves in joint angle space for the left and right hip and knee joints. We used 3D data projected into 2D and attempted to reconstruct the 3D information. We also were able to calculate limb lengths from this data.

The generated curves:

Movement of Left Hip

Movement of Right Hip

Movement of Left Knee

Movement of Right Knee

Movement of Left Hip and Knee

Movement of Right Hip and Knee

Movement of Both Hips

Movement of Both Knees

How this may be improved:

This could be improved so it can use real motion capture data.
More rigorous geometry calculations used to test for feasibility of joint angles and limb lengths.
Recognition of behavior to better fill in gaps in data due to occlusion.

The Code:

tracking tar ball

The Creators:

The algorithms for the Tracking Interrupting Cows were developed by Gary Yngve and Alison Smith, junior computer science majors at Georgia Tech.
Gary may be contacted at
Alison may be contacted at

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