U4D

<p align="right">English | <a href="./README_CN.md">简体中文</a></p> <p align="center"> <h1 align="center"> <strong>U4D: Uncertainty-Aware 4D World Modeling from LiDAR Sequences</strong> </h1> <p align="center"> <a href="https://xiangxu-0103.github.io/" target="_blank">Xiang Xu</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="https://alanliang.vercel.app/" target="_blank">Ao Liang</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="" target="_blank">Youquan Liu</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="" target="_blank">Linfeng Li</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="https://ldkong.com/" target="_blank">Lingdong Kong</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="https://liuziwei7.github.io/" target="_blank">Ziwei Liu</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href="" target="_blank">Qingshan Liu</a>&nbsp;&nbsp;&nbsp;&nbsp; </p> <p align="center"> <a href="https://arxiv.org/abs/2512.02982" target="_blank"><img src="https://img.shields.io/badge/Paper-%F0%9F%93%96-darkred"></a>&nbsp; <a href="" target="_blank"><img src="https://img.shields.io/badge/Project-%F0%9F%94%97-blue"></a>&nbsp; <a href="" target="_blank"><img src="https://img.shields.io/badge/Dataset-%F0%9F%94%97-green"></a>&nbsp; <a href="" target="_blank"><img src="https://visitor-badge.laobi.icu/badge?page_id=worldbench.U4D"></a> </p> </p> <img src="images/teaser.png" alt="Teaser" width="100%">

In this work, we introduce U4D, an uncertainty-aware framework for 4D LiDAR world modeling. The main contributions are:

• We introduce the first uncertainty-aware LiDAR generation framework that explicitly models spatial difficulty to enhance reliability in 4D world modeling.
• We design a two-stage hard-to-easy generation paradigm that reconstructs uncertain regions first and then completes the full scene under these priors.
• We develop a Mixture of Spatio-Temporal (MoST) block that ensures temporal consistency across frames by adaptively balancing spatial geometry and temporal dynamics.

:books: Citation

If you find this work helpful for your research, please kindly consider citing our paper:

@article{xu2025U4D,
    title   = {{U4D}: Uncertainty-Aware {4D} World Modeling from {LiDAR} Sequences},
    author  = {Xu, Xiang and Liang, Ao and Liu, Youquan and Li, Linfeng and Kong, Lingdong and Liu, Ziwei and Liu, Qingshan},
    journal = {arXiv preprint arXiv: 2512.02982},
    year    = {2025}
}

Updates

• [12.2025] - The technical report of U4D is available on arXiv.

License

This work is under the <a rel="license" href="https://www.apache.org/licenses/LICENSE-2.0">Apache License Version 2.0</a>, while some specific implementations in this codebase might be with other licenses. Kindly refer to LICENSE.md for a more careful check, if you are using our code for commercial matters.

Acknowledgements

This work is developed based on the R2DM codebase.