Accurate 3D object detection in large-scale outdoor scenes, characterized by considerable variations in object scales, necessitates features rich in both long-range and fine-grained information. While recent detectors have utilized window-based transformers to model long-range dependencies, they tend to overlook fine-grained details. To bridge this gap, we propose MsSVT++, an innovative Mixed-scale Sparse Voxel Transformer that simultaneously captures both types of information through a divide-and-conquer approach. This approach involves explicitly dividing attention heads into multiple groups, each responsible for attending to information within a specific range. The outputs of these groups are subsequently merged to obtain final mixed-scale features. To mitigate the computational complexity associated with applying a window-based transformer in 3D voxel space, we introduce a novel Chessboard Sampling strategy and implement voxel sampling and gathering operations sparsely using a hash map. Moreover, an important challenge stems from the observation that non-empty voxels are primarily located on the surface of objects, which impedes the accurate estimation of bounding boxes. To overcome this challenge, we introduce a Center Voting module that integrates newly voted voxels enriched with mixed-scale contextual information towards the centers of the objects, thereby improving precise object localization. Extensive experiments demonstrate that our single-stage detector, built upon the foundation of MsSVT++, consistently delivers exceptional performance across diverse datasets.

3D 目标检测中的突出问题是大规模室外场景下对象尺度的变化，需要同时获取远距离和细粒度信息的特征。为了解决这一问题，我们提出了MsSVT++，一种创新的混合尺度稀疏体素变换器，通过分治方法同时捕捉两类信息。使用棋盘采样策略和哈希映射在3D体素空间中进行稀疏的体素采样和聚集操作，以减轻基于窗口的变换器的计算复杂性。同时，引入了中心投票模块，将混合尺度上下文信息丰富的新体素朝着对象中心进行集成，从而提高了精确的对象定位。广泛的实验证明，我们的单阶段检测器在MsSVT++的基础上，对不同的数据集始终表现出优异的性能。

MsSVT++: 混合尺度稀疏体素变换与中心投票用于3D物体检测