Session of Innovation Showcase (May 16, 2026)
https://icmc2026.ligeti-zentrum.de/event/innovation-showcase/

Takayuki Rai and Haruka Hirayama: Motion Capture: Mocopi and Sound Interaction in Max

This paper presents a Local Space–based motion Analysis framework using Sony’s Mocopi motion capture system, implemented in the Max environment for real-time Audio interaction. The framework is designed for live Performance and interactive demonstration. In previous work, joint position data transmitted from Mocopi were converted into World Space coordinates and applied to audio and visual interaction. While this approach enabled various interaction designs, it revealed a fundamental limitation: identical body movements produced different coordinate values depending on the performer’s facing direction. This weakened the intuitive correspondence between bodily sensation and control data, particularly in performance and improvisational contexts. To address this issue, the present study introduces a Local Space representation defined relative to the performer’s body orientation. Joint positions are transformed from World Space into a forward-facing, body-relative coordinate frame that moves and rotates with the performer. This enables consistent detection of body movements regardless of orientation on stage, preserving the perceptual relationship between physical action and control data. Based on this framework, several Max external objects were developed to estimate body orientation, convert Joint positions into Local Space, and compute motion Features such as movement distance, direction, and angular change. Application examples demonstrate that movement-based Audio control becomes more stable and intuitive in Local Space. The system was evaluated through Poster + Demo presentations with a Mocopi-equipped performer, highlighting its suitability for interactive performance and artistic applications.