LEGO: A Lifting-Free Approach for Exocentric-to-Egocentric Video Generation

Hugging Face Daily Papers Papers

Summary

LEGO 提出一种无提升(lifting-free)的方法,用 LVSM 风格的 Transformer 直接合成第一人称视角,替代传统的深度估计与点云重投影管线,并将结果作为条件输入视频扩散模型,在跨视角视频生成上超越现有 SOTA 且能跨数据集泛化。

Generating an egocentric video from a single exocentric recording is a challenging case of novel view synthesis, as the two cameras share little overlap and much of the target view is unobserved. Current state-of-the-art methods reconstruct the scene explicitly by estimating depth, lifting the video into a point cloud, and re-rendering it from the egocentric camera to condition a video diffusion model. This deterministic mapping assigns each pixel to a single reprojected location, which preserves texture but translates depth errors into misplaced content. We ask what a video diffusion model should receive as its condition and propose a lifting-free answer: a learned view synthesizer, an LVSM-style transformer fine-tuned to render the egocentric view directly without depth, point clouds, or reprojection, resolving cross-view correspondence internally. In contrast, its probabilistic mapping averages each region over candidate source locations according to a learned correspondence distribution, preserving structure while fine texture is averaged away. We argue that this trade-off suits a diffusion generator, whose denoising training excels at restoring detail, so an effective condition should prioritize structural alignment over sharpness. This distribution's concentration also yields a per-region confidence, used both to mask low-confidence regions and to guide the generator toward high-confidence areas during early layout-forming denoising steps. Our approach consistently outperforms the state-of-the-art explicit pipeline and generalizes to other datasets without retraining. The synthesizer thus supplies view structure, and the diffusion model its detail.
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Source: https://huggingface.co/papers/2610.12442

Abstract

Generatinganegocentricvideofromasingleexocentricrecordingisachallengingcaseofnovelviewsynthesis,asthetwocamerassharelittleoverlapandmuchofthetargetviewisunobserved.Currentstate-of-the-artmethodsreconstructthesceneexplicitlybyestimatingdepth,liftingthevideointoapointcloud,andre-renderingitfromtheegocentriccameratoconditionavideodiffusionmodel.Thisdeterministicmappingassignseachpixeltoasinglereprojectedlocation,whichpreservestexturebuttranslatesdeptherrorsintomisplacedcontent.Weaskwhatavideodiffusionmodelshouldreceiveasitsconditionandproposealifting-freeanswer:alearnedviewsynthesizer,anLVSM-styletransformerfine-tunedtorendertheegocentricviewdirectlywithoutdepth,pointclouds,orreprojection,resolvingcross-viewcorrespondenceinternally.Incontrast,itsprobabilisticmappingaverageseachregionovercandidatesourcelocationsaccordingtoalearnedcorrespondencedistribution,preservingstructurewhilefinetextureisaveragedaway.Wearguethatthistrade-offsuitsadiffusiongenerator,whosedenoisingtrainingexcelsatrestoringdetail,soaneffectiveconditionshouldprioritizestructuralalignmentoversharpness.Thisdistribution’sconcentrationalsoyieldsaper-regionconfidence,usedbothtomasklow-confidenceregionsandtoguidethegeneratortowardhigh-confidenceareasduringearlylayout-formingdenoisingsteps.Ourapproachconsistentlyoutperformsthestate-of-the-artexplicitpipelineandgeneralizestootherdatasetswithoutretraining.Thesynthesizerthussuppliesviewstructure,andthediffusionmodelitsdetail.

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