AMOR

Airborne Motion Reconstruction via
Homotopy-Aware Trajectory Optimization

Seoul National University
SIGGRAPH 2026
AMOR teaser figure showing recovered airborne motion

Given a monocular in-the-wild video of a tumbling motion (top), our method refines noisy HMR estimates (bottom right) into physically plausible 3D airborne motion (bottom left). Red arrows indicate angular momentum, demonstrating improved physical plausibility in our result.

Abstract

Monocular video-based human mesh recovery (HMR) has made significant progress in recent years, yet existing methods often fail to reconstruct physically plausible motion during highly dynamic airborne movements such as jumping or acrobatics. These failure cases arise from motion blur, rapid orientation changes, and the lack of suitable training data, leading to temporally inconsistent and physically implausible results. We propose a novel method for reconstructing 3D airborne motion by refining inaccurate estimates produced by state-of-the-art HMR systems. Our approach extracts key physical quantities, identifies reliable motion segments based on physical consistency, and connects them using a homotopy-aware trajectory optimization. A global angular momentum constraint is then enforced over the entire motion, and global motion and local poses are jointly optimized under physical and temporal smoothness constraints. Experiments on challenging in-the-wild videos demonstrate that our method produces more physically consistent and temporally coherent airborne motions than existing refinement approaches.

Homotopy Classes of Rotational Trajectory

Three rotational paths between the same start and end orientations, illustrating different homotopy classes
An example of homotopically distinct rotation trajectories with identical start and end configurations. Top: Single full rotation (2π) resulting in quaternion sign change (q−q). Middle: Identity path with minimal rotation. Bottom: Double full rotation (4π) returning to original quaternion (qq). The rightmost column shows the corresponding trajectories on the unit quaternion space where antipodal points q (blue) and −q (red) represent the same SO(3) rotation. The trajectories belong to different homotopy classes and cannot be continuously deformed into one another. The top trajectory lies in a non-trivial class (e.g., 2π, 6π, ...) that involves a sign change, while the middle and bottom trajectories belong to the trivial class (e.g., 0, 4π, 8π, ...) with different rotation magnitudes.

Results

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BibTeX

@inproceedings{10.1145/3799902.3811070,
    author    = {Kim, Chanha and Won, Jungdam},
    title     = {AMOR: Airborne Motion Reconstruction via Homotopy-Aware Trajectory Optimization},
    year      = {2026},
    doi       = {10.1145/3799902.3811070},
    booktitle = {SIGGRAPH Conference Papers '26},
}