Dr. Li (Luis) LI

Selected Publications

1. 

   RAPiD-Seg: Range-Aware Pointwise Distance Distribution Networks for 3D LiDAR Segmentation

   Li Li, Hubert P. H. Shum, and Toby P. Breckon

   In European Conference on Computer Vision (ECCV), 2024

   🏆 Oral Presentation (2.3% = 200/8585)

   Abs arXiv Bib Preview PAPER Code Poster Video Oral

            

   3D point clouds play a pivotal role in outdoor scene perception, especially in the context of autonomous driving. Recent advancements in 3D LiDAR segmentation often focus intensely on the spatial positioning and distribution of points for accurate segmentation. However, these methods, while robust in variable conditions, encounter challenges due to sole reliance on coordinates and point intensity, leading to poor isometric invariance and suboptimal segmentation. To tackle this challenge, our work introduces Range-Aware Pointwise Distance Distribution (RAPiD) features and the associated RAPiD-Seg architecture. Our RAPiD features exhibit rigid transformation invariance and effectively adapt to variations in point density, with a design focus on capturing the localized geometry of neighboring structures. They utilize inherent LiDAR isotropic radiation and semantic categorization for enhanced local representation and computational efficiency, while incorporating a 4D distance metric that integrates geometric and surface material reflectivity for improved semantic segmentation. To effectively embed high-dimensional RAPiD features, we propose a double-nested autoencoder structure with a novel class-aware embedding objective to encode high-dimensional features into manageable voxel-wise embeddings. Additionally, we propose RAPiD-Seg which incorporates a channel-wise attention fusion and two effective RAPiD-Seg variants, further optimizing the embedding for enhanced performance and generalization. Our method outperforms contemporary LiDAR segmentation work in terms of mIoU on SemanticKITTI (76.1) and nuScenes (83.6) datasets.

   @inproceedings{li2024rapidseg,
     title = {{{RAPiD-Seg}}: {{Range-Aware}} {{Pointwise Distance Distribution}} {{Networks}} for {{3D LiDAR Segmentation}}},
     gh_repo = {rapid_seg},
     author = {Li, Li and Shum, Hubert P. H. and Breckon, Toby P.},
     keywords = {point cloud, semantic segmentation, invariance feature, pointwise distance distribution, autonomous driving},
     year = {2024},
     month = jul,
     publisher = {{Springer}},
     booktitle = {European Conference on Computer Vision (ECCV)},
     note = {🏆 <strong style="color:#CC0000;">Oral Presentation</strong> (2.3% = 200/8585)}
   }

2. 

   Less Is More: Reducing Task and Model Complexity for 3D Point Cloud Semantic Segmentation

   Li Li, Hubert P. H. Shum, and Toby P. Breckon

   In Conference on Computer Vision and Pattern Recognition (CVPR), 2023

   Abs arXiv Bib Preview PAPER Code Poster Video Website

            

   Whilst the availability of 3D LiDAR point cloud data has significantly grown in recent years, annotation remains expensive and time-consuming, leading to a demand for semi-supervised semantic segmentation methods with application domains such as autonomous driving. Existing work very often employs relatively large segmentation backbone networks to improve segmentation accuracy, at the expense of computational costs. In addition, many use uniform sampling to reduce ground truth data requirements for learning needed, often resulting in sub-optimal performance. To address these issues, we propose a new pipeline that employs a smaller architecture, requiring fewer ground-truth annotations to achieve superior segmentation accuracy compared to contemporary approaches. This is facilitated via a novel Sparse Depthwise Separable Convolution module that significantly reduces the network parameter count while retaining overall task performance. To effectively sub-sample our training data, we propose a new Spatio-Temporal Redundant Frame Downsampling (ST-RFD) method that leverages knowledge of sensor motion within the environment to extract a more diverse subset of training data frame samples. To leverage the use of limited annotated data samples, we further propose a soft pseudo-label method informed by LiDAR reflectivity. Our method outperforms contemporary semi-supervised work in terms of mIoU, using less labeled data, on the SemanticKITTI (59.5@5%) and ScribbleKITTI (58.1@5%) benchmark datasets, based on a 2.3× reduction in model parameters and 641x fewer multiply-add operations whilst also demonstrating significant performance improvement on limited training data (i.e., Less is More).

   @inproceedings{li2023less,
     title = {{{Less Is More}}: {{Reducing Task}} and {{Model Complexity}} for {{3D Point Cloud Semantic Segmentation}}},
     gh_repo = {lim3d},
     author = {Li, Li and Shum, Hubert P. H. and Breckon, Toby P.},
     keywords = {point cloud, semantic segmentation, sparse convolution, depthwise separable convolution, autonomous driving},
     year = {2023},
     month = jun,
     publisher = {{IEEE}},
     booktitle = {Conference on Computer Vision and Pattern Recognition (CVPR)},
   }

3. 

   TraIL-Det: Transformation-Invariant Local Feature Networks for 3D LiDAR Object Detection with Unsupervised Pre-Training

   Li Li, Tanqiu Qiao, Hubert P. H. Shum, and Toby P. Breckon

   In British Machine Vision Conference (BMVC), 2024

   Abs arXiv Bib Preview PAPER Code Poster

            

   3D point clouds are essential for perceiving outdoor scenes, especially within the realm of autonomous driving. Recent advances in 3D LiDAR Object Detection focus primarily on the spatial positioning and distribution of points to ensure accurate detection. However, despite their robust performance in variable conditions, these methods are hindered by their sole reliance on coordinates and point intensity, resulting in inadequate isometric invariance and suboptimal detection outcomes. To tackle this challenge, our work introduces Transformation-Invariant Local (TraIL) features and the associated TraIL-Det architecture. Our TraIL features exhibit rigid transformation invariance and effectively adapt to variations in point density, with a design focus on capturing the localized geometry of neighboring structures. They utilize the inherent isotropic radiation of LiDAR to enhance local representation, improve computational efficiency, and boost detection performance. To effectively process the geometric relations among points within each proposal, we propose a Multi-head self-Attention Encoder (MAE) with asymmetric geometric features to encode high-dimensional TraIL features into manageable representations. Our method outperforms contemporary self-supervised 3D object detection approaches in terms of mAP on KITTI (67.8, 20% label, moderate) and Waymo (68.9, 20% label, moderate) datasets under various label ratios (20%, 50%, and 100%).

   @inproceedings{li24trail,
     gh_repo = {rapid_seg},
     author = {Li, Li and Qiao, Tanqiu and Shum, Hubert P. H. and Breckon, Toby P.},
     title = {{TraIL-Det: Transformation-Invariant Local Feature Networks for 3D LiDAR Object Detection with Unsupervised Pre-Training}},
     booktitle = {British Machine Vision Conference (BMVC)},
     year = {2024},
     month = jul,
     publisher = {BMVA},
     keywords = {autonomous driving, LiDAR, 3D, point cloud, object detection, invariance feature},
     category = {automotive 3Dvision},
   }

4. 

   DurLAR: A High-Fidelity 128-Channel LiDAR Dataset with Panoramic Ambient and Reflectivity Imagery for Multi-Modal Autonomous Driving Applications

   Li Li, K.N. Ismail, Hubert P. H. Shum, and Toby P. Breckon

   In International Conference on 3D Vision (3DV), 2021

   Abs arXiv Bib Preview PAPER Poster Video Website

          

   We present DurLAR, a high-fidelity 128-channel 3D LiDAR dataset with panoramic ambient (near infrared) andreflectivity imagery, as well as a sample benchmark usingdepth estimation for autonomous driving applications. Ourdriving platform is equipped with a high resolution 128channel LiDAR, a 2MPix stereo camera, a lux meter anda GNSS/INS system. Ambient and reflectivity images aremade available along with the LiDAR point clouds to facilitate multi-modal use of concurrent ambient and reflectivityscene information. Leveraging DurLAR, with a resolutionexceeding that of prior benchmarks, we consider the task ofmonocular depth estimation and use this increased availability of higher resolution, yet sparse ground truth scenedepth information to propose a novel joint supervised/self-supervised loss formulation. We compare performance overboth our new DurLAR dataset, the established KITTI benchmark and the Cityscapes dataset. Our evaluation shows ourjoint use supervised and self-supervised loss terms, enabledvia the superior ground truth resolution and availabilitywithin DurLAR improves the quantitative and qualitativeperformance of leading contemporary monocular depth es-timation approaches (RMSE= 3.639,SqRel= 0.936).

   @inproceedings{li21durlar,
     gh_repo = {durlar},
     author = {Li, Li and Ismail, K.N. and Shum, Hubert P. H. and Breckon, Toby P.},
     title = {{{DurLAR}}: A {{High-Fidelity}} {{128-Channel}} {{LiDAR Dataset}} with {{Panoramic Ambient and Reflectivity Imagery}} for {{Multi-Modal}} {{Autonomous Driving Applications}}},
     booktitle = {International Conference on 3D Vision (3DV)},
     year = {2021},
     month = dec,
     publisher = {IEEE},
     keywords = {autonomous driving, dataset, high resolution LiDAR, flash LiDAR, ground truth depth, dense depth, monocular depth estimation, stereo vision, 3D},
     category = {automotive 3Dvision},
   }

5. 

   Dur360BEV: A Real-world Single 360-degree Camera Dataset and Benchmark for Bird-Eye View Mapping in Autonomous Driving

   Wenke E, Chao Yuan, Li Li, Yixin Sun, Yona Falinie A. Gaus, and 2 more authors

   In IEEE Int. Conf. Robot. Autom, 2025

   Abs arXiv Bib Preview PAPER Website

          

   We present Dur360BEV, a novel spherical camera autonomous driving dataset equipped with a high-resolution 128-channel 3D LiDAR and a RTK-refined GNSS/INS system, along with a benchmark architecture designed to generate Bird-Eye-View (BEV) maps using only a single spherical camera. This dataset and benchmark address the challenges of BEV generation in autonomous driving, particularly by reducing hardware complexity through the use of a single 360-degree camera instead of multiple perspective cameras. Within our benchmark architecture, we propose a novel spherical-image-to-BEV (SI2BEV) module that leverages spherical imagery and a refined sampling strategy to project features from 2D to 3D. Our approach also includes an innovative application of Focal Loss, specifically adapted to address the extreme class imbalance often encountered in BEV segmentation tasks. Through extensive experiments, we demonstrate that this application of Focal Loss significantly improves segmentation performance on the Dur360BEV dataset. The results show that our benchmark not only simplifies the sensor setup but also achieves competitive performance.

   @inproceedings{e2025durlar360,
     title = {{Dur360BEV}: A {Real-world} {Single} {360-degree} {Camera} {Dataset} and {Benchmark} for {Bird-Eye} {View} {Mapping} in {Autonomous} {Driving}},
     booktitle = {IEEE Int. Conf. Robot. Autom},
     author = {E, Wenke and Yuan, Chao and Li, Li and Sun, Yixin and Gaus, Yona Falinie A. and Atapour-Abarghouei, Amir and Breckon, Toby P.},
     publisher = {IEEE},
     year = {2025},
     month = jan,
   }

6. 

   TOMD: A Trail-based Off-road Multimodal Dataset for Traversable Pathway Segmentation under Challenging Illumination Conditions

   Yixin Sun, Li Li, Wenke E, Amir Atapour-Abarghouei, and Toby P. Breckon

   In Int. Joint Conf. on Neural Networks, 2025

   Abs Bib

          

   Detecting traversable pathways in unstructured outdoor environments remains a significant challenge for autonomous robots, especially in critical applications such as wide-area search and rescue, as well as in incident management scenarios such as forest fires. Current datasets and models primarily focus on either urban environments or wide vehicle-traversable off-road tracks, leaving a substantial gap in tackling the complexities of trail-based off-road scenarios. To address this issue, we introduce the Trail-based Off-road Multimodal Dataset (TOMD), a comprehensive dataset explicitly designed for narrow and unstructured trail-like environments. Our dataset features high-fidelity multimodal sensor data — including 128-channel LiDAR, stereo imagery, GNSS, IMU, and illumination measurements — collected through repeated runs across diverse environmental conditions. In addition, we propose a novel dynamic multiscale data fusion model for precise traversable pathway prediction in trail-like areas. The study investigates the impact of various fusion processes — early, cross, and mixed — on model performance under different illumination levels: low-light, normal ambient lighting, and bright conditions. The results highlight the effectiveness of our approach, performance variations across different illumination levels, and the potential applicability of the dataset in diverse environmental conditions.

   @inproceedings{sun2025tomd,
     title = {{{TOMD: A Trail-based Off-road Multimodal Dataset for Traversable Pathway Segmentation under Challenging Illumination Conditions}}},
     booktitle = {Int. Joint Conf. on Neural Networks},
     author = {Sun, Yixin and Li, Li and E, Wenke and Atapour-Abarghouei, Amir and Breckon, Toby P.},
     year = {2025},
   }

7. 

   An Empirical Study of Training State-of-the-Art LiDAR Segmentation Models

   Jiahao Sun, Xiang Xu, Lingdong Kong, Youquan Liu, Li Li, and 8 more authors

   2024

   Abs arXiv Bib Preview PAPER Code

        

   In the rapidly evolving field of autonomous driving, precise segmentation of LiDAR data is crucial for understanding complex 3D environments. Traditional approaches often rely on disparate, standalone codebases, hindering unified advancements and fair benchmarking across models. To address these challenges, we introduce MMDetection3D-lidarseg, a comprehensive toolbox designed for the efficient training and evaluation of state-of-the-art LiDAR segmentation models. We support a wide range of segmentation models and integrate advanced data augmentation techniques to enhance robustness and generalization. Additionally, the toolbox provides support for multiple leading sparse convolution backends, optimizing computational efficiency and performance. By fostering a unified framework, MMDetection3D-lidarseg streamlines development and benchmarking, setting new standards for research and application. Our extensive benchmark experiments on widely-used datasets demonstrate the effectiveness of the toolbox. The codebase and trained models have been publicly available, promoting further research and innovation in the field of LiDAR segmentation for autonomous driving.

   @misc{sun2024empirical,
     title = {An {{Empirical Study}} of {{Training State-of-the-Art LiDAR Segmentation Models}}},
     gh_repo = {open-mmlab/mmdetection3d},
     author = {Sun, Jiahao and Xu, Xiang and Kong, Lingdong and Liu, Youquan and Li, Li and Zhu, Chenming and Zhang, Jingwei and Xiao, Zeqi and Chen, Runnan and Wang, Tai and Zhang, Wenwei and Chen, Kai and Qing, Chunmei},
     year = {2024},
     number = {arXiv:2405.14870},
     eprint = {2405.14870},
     primaryclass = {cs},
     publisher = {arXiv},
     doi = {10.48550/arXiv.2405.14870},
     urldate = {2024-05-25},
   }