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Lucida: Parse, Generate, and Place for Composable Real-to-Sim Scene Modeling

Converts posed indoor RGB(-D) video into editable, simulation-ready 3D scene graphs by parsing multi-view evidence into per-object bundles, generating complete object assets from that evidence, and placing them with GizmoAct, a VLM policy that refines 9-DoF poses through closed-loop GUI actions.

Introduction

Most real captures of indoor scenes are cluttered, occluded, and incomplete, so insisting on perfect instance geometry up front forces brittle pipelines. The core insight here is to defer precision: parse multi-view evidence to discover instances, generate complete object assets conditioned on that evidence, and reach metric accuracy only at the end by closed-loop placement. This lets each stage consume what real captures reliably provide and tolerates occlusion and model–observation mismatch.

Key Findings
  • Redistribution of responsibilities: parsing produces a scene graph whose nodes carry multi-view evidence bundles (images, partial point clouds, representative boxes, and referring text) rather than requiring clean crops or full reconstructions, and generation conditions on those bundles to synthesize occluder-free views and lift them into 3D assets.
  • GizmoAct placement: frames asset placement as multi-turn GUI interaction. A pretrained VLM is finetuned and RL-refined to operate a 3D editor gizmo in closed loop, predicting incremental pose edits and when to stop—robust to coarse initialization and asset–observation geometry mismatch.
  • Empirical gains: large improvements across tasks—scene-level 3D object detection mAP rises substantially on R2S-Scene (+69% over Boxer in the reported protocol), [email protected] increases from 57.8% to 83.4% on CA-1M for pose refinement, and scene F-Score rises from 0.794 (SAM 3D) to 0.924 for full-system reconstruction.
Who it's for + tradeoffs

Great fit if you need to convert real indoor capture videos into editable, sim-ready digital twins for embodied AI, robotics simulation, or dataset generation and you expect cluttered, partially observed objects. The method favors pipelines that can accept stochastic generation and closed-loop refinement rather than perfect upfront geometry.

Look elsewhere if you require guaranteed metric-accurate instance geometry from a single-shot input without any human-in-the-loop verification or if you cannot run learned VLM/RL policies for placement. The approach depends on synthetic expert trajectories for GizmoAct training and assumes access to posed RGB or RGB-D sequences.

Where it fits

Positioned between research on 3D object detection/pose refinement and real-to-sim scene reconstruction, it emphasizes composability (per-object assets + scene graph) and closed-loop placement to bridge perception and simulation for downstream policy learning and embodied evaluation.

Information

  • Websitearxiv.org
  • OrganizationsByteDance Seed, Peking University, Zhejiang University
  • AuthorsMinghan Qin, Yuang Wang, Xiuyu Yang, Yushi Long, Yujian Zhang, Ruihuan Wang, Kai Ye, Yangang Zhang, Hang Li
  • Published date2026/08/31

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