Researchers have developed HilDA (Hierarchical Distillation with Diffusion), a self-supervised pretraining framework for LiDAR backbones that addresses the scarcity of annotated data in autonomous driving. According to the paper published on arXiv, HilDA combines hierarchical distillation with a temporal occupancy diffusion objective to capture both semantic and geometric information.
The Data Scarcity Challenge
Leveraging Vision Foundation Models (VFMs) for camera-to-LiDAR knowledge distillation offers a promising solution to the scarcity of annotated data needed to represent the immense geometric and kinematic diversity of real-world autonomous driving, the researchers reported. However, current approaches typically treat VFMs as black-box teachers, relying exclusively on frame-wise feature similarity. Consequently, they do not fully exploit the teacher's layer-wise semantic structure and global context, as well as the rich spatiotemporal information inherent in LiDAR sequences.
HilDA's Hierarchical Distillation
HilDA proposes a self-supervised pretraining framework for LiDAR backbones that better captures the semantic what and geometric where needed for driving tasks. It combines hierarchical distillation comprising multi-layer distillation for progressive semantic alignment and global context distillation for scene-level semantics. This approach allows the model to learn from the teacher's layer-wise structure and global scene understanding.
Temporal Occupancy Diffusion
Additionally, HilDA incorporates a temporal occupancy diffusion objective that promotes spatiotemporal consistency. This objective ensures that the model is trained to predict future occupancy sequences, reinforcing the temporal coherence of the learned representations.
Benchmark Performance
According to the paper, models pre-trained with HilDA achieve state-of-the-art results on cross-modal distillation benchmarks and outperform models trained via prior distillation approaches on 3D object detection, scene flow, and semantic occupancy prediction. The paper reports these results across multiple benchmarks, indicating that the combined hierarchical and diffusion objectives yield superior performance for downstream autonomous driving tasks.
Models pre-trained with HilDA achieve state-of-the-art results on cross-modal distillation benchmarks and outperform models trained via prior distillation approaches on 3D object detection, scene flow, and semantic occupancy prediction.
The framework is designed to work with various LiDAR backbone architectures, and the authors have released code for reproducibility. The work contributes to the growing field of self-supervised learning for 3D perception, particularly for autonomous vehicles where labeled data is expensive and time-consuming to acquire.