SAFDNet: A Simple and Effective Network for Fully Sparse 3D Object Detection
Authors: Gang Zhang, Junnan Chen, Guohuan Gao, Jianmin Li, Si Liu, Xiaolin Hu

LiDAR-based 3D object detection plays an essential role in autonomous driving. Existing high-performing 3D object detectors usually build dense feature maps in the backbone network and prediction head. However the computational costs introduced by the dense feature maps grow quadratically as the perception range increases making these models hard to scale up to long-range detection. Some recent works have attempted to construct fully sparse detectors to solve this issue; nevertheless the resulting models either rely on a complex multi-stage pipeline or exhibit inferior performance. In this work we propose a fully sparse adaptive feature diffusion network (SAFDNet) for LiDAR-based 3D object detection. In SAFDNet an adaptive feature diffusion strategy is designed to address the center feature missing problem. We conducted extensive experiments on Waymo Open nuScenes and Argoverse2 datasets. SAFDNet performed slightly better than the previous SOTA on the first two datasets but much better on the last dataset which features long-range detection verifying the efficacy of SAFDNet in scenarios where long-range detection is required. Notably on Argoverse2 SAFDNet surpassed the previous best hybrid detector HEDNet by 2.6% mAP while being 2.1x faster and yielded 2.1% mAP gains over the previous best sparse detector FSDv2 while being 1.3x faster. The code will be available at https://github.com/zhanggang001/HEDNet.