S4R: Rethinking Point Cloud Sampling via Guiding Upsampling-Aware Perception

Point cloud sampling aims to derive a sparse point cloud from a relatively dense point cloud, which is essential for efficient data transmission and storage. While existing deep sampling methods prioritize preserving the perception of sampled point clouds for downstream networks, few studies have critically examined the rationale behind this goal. Specifically, we observe that sampling can lead to a perceptual degradation phenomenon in many influential downstream networks, impairing their ability to effectively process sampled point clouds. We theoretically reveal the nature of the phenomenon and attempt to construct a novel sampling target by uniting upsampling and perceptual reconstruction. Accordingly, we propose a Maximum A Posteriori (MAP) sampling framework named Sample for Reconstruct (S4R), which impels the sampling stage to infer upsampling-guided perception. In S4R, we design very simple but effective sampling and upsampling networks using residual-based graph convolutions and incorporate a pseudo-residual connection to introduce prior knowledge. This architecture takes advantage of reconstruction properties and allows the sampling network to be trained in an unsupervised manner. Extensive experiments on classical networks demonstrates the excellent performance of S4R compared with the previous sampling schemes and reveals its advantages on different point cloud downstream tasks, i.e., classification, reconstruction and segmentation.