BEVSpread: Spread Voxel Pooling for Bird's-Eye-View Representation in Vision-based Roadside 3D Object Detection
Authors: Wenjie Wang, Yehao Lu, Guangcong Zheng, Shuigen Zhan, Xiaoqing Ye, Zichang Tan, Jingdong Wang, Gaoang Wang, Xi Li

Vision-based roadside 3D object detection has attracted rising attention in autonomous driving domain since it encompasses inherent advantages in reducing blind spots and expanding perception range. While previous work mainly focuses on accurately estimating depth or height for 2D-to-3D mapping ignoring the position approximation error in the voxel pooling process. Inspired by this insight we propose a novel voxel pooling strategy to reduce such error dubbed BEVSpread. Specifically instead of bringing the image features contained in a frustum point to a single BEV grid BEVSpread considers each frustum point as a source and spreads the image features to the surrounding BEV grids with adaptive weights. To achieve superior propagation performance a specific weight function is designed to dynamically control the decay speed of the weights according to distance and depth. Aided by customized CUDA parallel acceleration BEVSpread achieves comparable inference time as the original voxel pooling. Extensive experiments on two large-scale roadside benchmarks demonstrate that as a plug-in BEVSpread can significantly improve the performance of existing frustum-based BEV methods by a large margin of (1.12 5.26 3.01) AP in vehicle pedestrian and cyclist.