DensER: Density-imbalance-Eased Representation for LiDAR-based Whole Scene Upsampling

With the development of depth sensors, 3D point cloud upsampling that generates a high-resolution point cloud given a sparse input becomes emergent. However, many previous works focused on single 3D object reconstruction and refinement. Although a few recent works began to discuss 3D structure refine-ment for a more complex scene, they do not target LiDAR-based point clouds, which have density imbalance issues from near to far. This paper proposed DensER, a Density-imbalance-Eased regional Representation. Notably, to learn robust representations and model local geometry under imbalance point density, we designed density-aware multiple receptive fields to extract the regional features. Moreover, founded on the patch reoccurrence property of a nature scene, we proposed a density-aided attentive module to enrich the extracted features of point-sparse areas by referring to other non-local regions. Finally, by coupling with novel manifold-based upsamplers, DensER shows the ability to super-resolve LiDAR-based whole-scene point clouds. The exper-imental results show DensER outperforms related works both in qualitative and quantitative evaluation. We also demonstrate that the enhanced point clouds can improve downstream tasks such as 3D object detection and depth completion.