Synthesizing physically plausible articulated human-object interactions (HOI) without 3D/4D supervision remains a fundamental challenge. While recent zero-shot approaches leverage video diffusion models to synthesize human-object interactions, they are largely confined to rigid-object manipulation and lack explicit 4D geometric reasoning. To bridge this gap, we formulate articulated HOI synthesis as a 4D reconstruction problem from monocular video priors: given only a video generated by a diffusion model, we reconstruct a full 4D articulated scene without any 3D supervision. This reconstruction-based approach treats the generated 2D video as supervision for an inverse rendering problem, recovering geometrically consistent and physically plausible 4D scenes that naturally respect contact, articulation, and temporal coherence. We introduce ArtHOI, the first zero-shot framework for articulated human-object interaction synthesis via 4D reconstruction from video priors. Our key designs are: 1) Flow-based part segmentation: leveraging optical flow as a geometric cue to disentangle dynamic from static regions in monocular video; 2) Decoupled reconstruction pipeline: joint optimization of human motion and object articulation is unstable under monocular ambiguity, so we first recover object articulation, then synthesize human motion conditioned on the reconstructed object states. ArtHOI bridges video-based generation and geometry-aware reconstruction, producing interactions that are both semantically aligned and physically grounded. Across diverse articulated scenes (e.g., opening fridges, cabinets, microwaves), ArtHOI significantly outperforms prior methods in contact accuracy, penetration reduction, and articulation fidelity, extending zero-shot interaction synthesis beyond rigid manipulation through reconstruction-informed synthesis.

翻译：在无3D/4D监督条件下合成物理合理的铰接式人-物交互（HOI）仍是一个基础性挑战。现有零样本方法虽能利用视频扩散模型合成人-物交互，但大多局限于刚性物体操控且缺乏显式的4D几何推理。为弥补这一缺陷，我们将铰接式HOI合成构建为基于单目视频先验的4D重建问题：仅通过扩散模型生成的视频，即可在无任何3D监督的情况下重建完整的4D铰接场景。这种基于重建的方法将生成的2D视频作为逆向渲染问题的监督信号，恢复出几何一致且物理合理的4D场景，天然满足接触约束、铰接结构与时间连贯性要求。我们提出ArtHOI——首个通过视频先验4D重建实现铰接式人-物交互合成的零样本框架。核心设计包括：1）基于光流的部件分割：利用光流作为几何线索，在单目视频中解耦动态与静态区域；2）解耦重建流程：针对单目歧义下人体运动与物体铰接联合优化的不稳定性，我们首先重建物体铰接状态，再基于重建的物体状态合成人体运动。ArtHOI架起了基于视频的生成方法与几何感知重建之间的桥梁，生成的交互既满足语义对齐又具备物理基础。在多样化铰接场景（如打开冰箱、橱柜、微波炉）中，ArtHOI在接触精度、穿透减少和铰接保真度方面显著优于现有方法，通过重建引导的合成将零样本交互合成拓展至刚性操控之外的领域。