Our grasshopper file contains multiple sections. The top video row is how the program senses where the calligraphy brush is and where the grid should go. The bottom video row if the system for locking the grid. If the marker is placed farther on the table the grid locks in place and the animation starts. 

The grasshopper program tracks and identifies Reactivision markers, an open-source computer vision framework similar to QR codes. The program chooses a character based on which marker is placed on the tabletop and orients it along a drawn contour at the point closest to the marker.