FreeCap: Hybrid Calibration-Free Motion Capture in Open Environments

We propose a novel hybrid calibration-free method FreeCap to accurately capture global multi-person motions in open environments. Our system combines a single LiDAR with expandable moving cameras, allowing for flexible and precise motion estimation in a unified world coordinate. In particular, We introduce a local-to-global pose-aware cross-sensor human-matching module that predicts the alignment among each sensor, even in the absence of calibration. Additionally, our coarse-to-fine sensor-expandable pose optimizer further optimizes the 3D human key points and the alignments, it is also capable of incorporating additional cameras to enhance accuracy. Extensive experiments on Human-M3 and FreeMotion datasets demonstrate that our method significantly outperforms state-of-the-art single-modal methods, offering an expandable and efficient solution for multi-person motion capture across various applications.

@article{xue2025_2411.04469,
  title={ FreeCap: Hybrid Calibration-Free Motion Capture in Open Environments },
  author={ Aoru Xue and Yiming Ren and Zining Song and Mao Ye and Xinge Zhu and Yuexin Ma },
  journal={arXiv preprint arXiv:2411.04469},
  year={ 2025 }
}