Camera-based 3D object detectors are welcome due to their wider deployment
and lower price than LiDAR sensors. We revisit the prior stereo modeling DSGN
about the stereo volume constructions for representing both 3D geometry and
semantics. We polish the stereo modeling and propose our approach, DSGN++,
aiming for improving information flow throughout the 2D-to-3D pipeline in the
following three main aspects. First, to effectively lift the 2D information to
stereo volume, we propose depth-wise plane sweeping (DPS) that allows denser
connections and extracts depth-guided features. Second, for better grasping
differently spaced features, we present a novel stereo volume -- Dual-view
Stereo Volume (DSV) that integrates front-view and top-view features and
reconstructs sub-voxel depth in the camera frustum. Third, as the foreground
region becomes less dominant in 3D space, we firstly propose a multi-modal data
editing strategy -- Stereo-LiDAR Copy-Paste, which ensures cross-modal
alignment and improves data efficiency. Without bells and whistles, extensive
experiments in various modality setups on the popular KITTI benchmark show that
our method consistently outperforms other camera-based 3D detectors for all
categories. Code will be released at https://github.com/chenyilun95/DSGN2