3D object detection is a critical component of autonomous driving, yet its performance degrades severely in adverse weather due to the degradation of LiDAR point clouds. While existing LiDAR-4D radar fusion methods enhance robustness by incorporating weather-robust 4D radar data, they often depend on well geometric structures from LiDAR and so struggle to effectively exploit radar data in case of degraded LiDAR data. To tackle this challenge, we propose REL, a novel 4D radar-guided LiDAR geometric enhancement framework. It utilizes 4D radar features to dynamically generate virtual LiDAR points, effectively increasing the density of degraded LiDAR data. Moreover, a Position-Guided Cross Attention (PGCA) module is proposed to enhance the feature representation of virtual points, while an Adaptive Feature Fusion (AFF) module is designed to integrate virtual and real LiDAR features. Extensive experiments on the K-Radar and Vod-Fog datasets demonstrate that REL achieves state-of-the-art 3D object detection performance under diverse adverse weather conditions. Notably, REL improves the overall AP3D by 9.3% on K-Radar and boosts the cyclist class by up to 52.9% 3D mAP under the most severe foggy condition on Vod-Fog.

In this paper, we present a dynamic learnable label assignment (DLLA) method for indoor anchor-free one-stage 3D object detection. Existing methods principally depend on hand-crafted strategies with fixed thresholds, which fail to adapt to the inherent variability in object characteristics such as size, shape, and occlusion levels. This lack of adaptability results in suboptimal sample assignments and unstable detection performance. To address this challenge, we map the features of proposals and ground truths separately into the same embedding space, enabling a dynamic strategy of assigning appropriate positive samples to each instance. Specifically, we first interact with the features of all proposals to effectively integrate information from each proposal in the scene and capture long-range dependencies between different locations. Additionally, to extract more discriminative and generalized features for positive and negative samples, we employ a contrastive learning process to optimize the elemental relationships and distances between proposals and ground truths. Finally, we introduce a denoising task to alleviate the difficulty of the unsupervised learning process in DLLA. Experimental results show that our DLLA outperforms other methods on three popular indoor datasets (ScanNet V2, SUN RGB-D, and ScanNet200).