UniCon3R: Contact-aware 3D Human-Scene Reconstruction from Monocular Video

We introduce UniCon3R (Unified Contact-aware 3D Reconstruction), a unified feed-forward framework for online human-scene 4D reconstruction from monocular videos. Recent feed-forward methods enable real-time world-coordinate human motion and scene reconstruction, but they often produce physically implausible artifacts such as bodies floating above the ground or penetrating parts of the scene. The key reason is that existing approaches fail to model physical interactions between the human and the environment. A natural next step is to predict human-scene contact as an auxiliary output -- yet we find this alone is not sufficient: contact must actively correct the reconstruction. To address this, we explicitly model interaction by inferring 3D contact from the human pose and scene geometry and use the contact as a corrective cue for generating the final pose. This enables UniCon3R to jointly recover high-fidelity scene geometry and spatially aligned 3D humans within the scene. Experiments on standard human-centric video benchmarks such as RICH, EMDB, 3DPW and SLOPER4D show that UniCon3R outperforms state-of-the-art baselines on physical plausibility and global human motion estimation while achieving real-time online inference. We experimentally demonstrate that contact serves as a powerful internal prior rather than just an external metric, thus establishing a new paradigm for physically grounded joint human-scene reconstruction. Project page is available at https://surtantheta.github.io/UniCon3R .

Improving Human Motion Plausibility with Body Momentum

Many studies decompose human motion into local motion in a frame attached to the root joint and global motion of the root joint in the world frame, treating them separately. However, these two components are not independent. Global movement arises from interactions with the environment, which are, in turn, driven by changes in the body configuration. Motion models often fail to precisely capture this physical coupling between local and global dynamics, while deriving global trajectories from joint torques and external forces is computationally expensive and complex. To address these challenges, we propose using whole-body linear and angular momentum as a constraint to link local motion with global movement. Since momentum reflects the aggregate effect of joint-level dynamics on the body's movement through space, it provides a physically grounded way to relate local joint behavior to global displacement. Building on this insight, we introduce a new loss term that enforces consistency between the generated momentum profiles and those observed in ground-truth data. Incorporating our loss reduces foot sliding and jitter, improves balance, and preserves the accuracy of the recovered motion. Code and data are available at the project page https://hlinhn.github.io/momentum_bmvc.

OfCaM: Global Human Mesh Recovery via Optimization-free Camera Motion Scale Calibration

Accurate camera motion estimation is critical to estimate human motion in the global space. A standard and widely used method for estimating camera motion is Simultaneous Localization and Mapping (SLAM). However, SLAM only provides a trajectory up to an unknown scale factor. Different from previous attempts that optimize the scale factor, this paper presents Optimization-free Camera Motion Scale Calibration (OfCaM), a novel framework that utilizes prior knowledge from human mesh recovery (HMR) models to directly calibrate the unknown scale factor. Specifically, OfCaM leverages the absolute depth of human-background contact joints from HMR predictions as a calibration reference, enabling the precise recovery of SLAM camera trajectory scale in global space. With this correctly scaled camera motion and HMR's local motion predictions, we achieve more accurate global human motion estimation. To compensate for scenes where we detect SLAM failure, we adopt a local-to-global motion mapping to fuse with previously derived motion to enhance robustness. Simple yet powerful, our method sets a new standard for global human mesh estimation tasks, reducing global human motion error by 60% over the prior SOTA while also demanding orders of magnitude less inference time compared with optimization-based methods.