I wrote a Kinect-based application I call “Free Bodies. Diagrammed.” whose purpose is to reveal the real physics of a physical experience.
The range of motion of a healthy human shoulder moving in the coronal plane is not particularly difficult to measure. With no tools and only a brief explanation of basic geometry and anatomical planes, the average person could easily identify 180+ degrees of rotation simply by moving their arm. That said, I found the notion of interactively demonstrating some of the basic physics we have covered in class to be a worthy project for our second assignment.
The application maps the rotation of the left shoulder in real time and performs several other measurements and calculations along the way. The application measures the angle of travel in the coronal plane away from the position of the arm at rest. It also measures the distance of the left hand from the left shoulder (only in the coronal plane). Inspired by the example in class, from these it instantaneously calculates and displays the torque necessary to statically suspend an imaginary can of soup at one’s side (the arm itself is considered to be massless). The intended use is to hold a can of soup and feel the experience of the torque while mapping the visceral experience to live data display. Varying one’s shoulder angle and even bending one’s elbow instantaneously reveal the changes in torque felt at the shoulder to suspend a soup can. In this way, the relationship of angle and perpendicular distance to torque can be directly experienced bodily and mentally.
While not a perfect approach, by largely ignoring depth components of the skeleton, the X-Y plot of the joint data is a natural projection of the coronal plane of the body. The Kinect can track up to two skeletons. By using the calculated arm length and shoulder angle together with various joint coordinates, the application is able to draw the data hovering near relevant locations on the body; in this way two skeletons and their data can be naturally displayed (people cannot occupy the same points in 3D space and thus as an added benefit will naturally position themselves for the best data display).
