Real-time visualization of sword trajectories in fencing matches

We developed a system called Sword Tracer that visualizes sword trajectories in fencing matches. Sword Tracer tracks the tips of the swords in the image coordinates and visualizes their movements with computer graphics (CGs). It measures each sword’s position in the infrared (IR) image by detecting IR light reflected from retroreflective tape placed on the tip of the sword. It uses only a single camera and a single marker at the tip, so the system is compact enough to be used in official fencing matches. It accurately detects the tips of the swords by using supervised machine learning and tracks them by predicting their positions in the next frame. The trajectory CGs of the sword tips can be composited on the broadcast image in real-time. Sword Tracer was first used for a broadcast at the All Japan Fencing Championships in December 2017 and has since been used for four other broadcast programs and five exhibition events from 2018 to 2020. TV viewers and guests at the events approved of this new video effect because it helped them to follow the fast-moving swords and gain a better understanding of the swordplay.