Deep learning-based methods have become the dominant solution for point cloud denoising, offering strong generalization capabilities through data-driven training. However, traditional methods, despite their drawbacks of heavy parameter tuning and weak generalization, retain unique advantages in interpretability and theoretical robustness. This complementarity motivates us to explore a hybrid solution that leverages data-driven paradigms to overcome the performance constraints of traditional methods. In this paper, we revisit the classic bilateral filter (BF) as a case study and identify three key limitations hindering its performance: excessive parameter tuning, suboptimal neighborhood quality, and fixed parameters across the entire model. To address them, we propose CustomBF, a novel framework for customizing BF components at a per-point level. CustomBF employs multigraph encoders and a mutual guidance strategy to analyze local patches, enabling the customization of BF components including center point normal, neighborhood point coordinates, Gaussian function parameters, and neighborhood radius for each point. Experimental results demonstrate that this component-customized bilateral filter outperforms state-of-the-art methods and achieves robust denoising even in complex scenarios. It highlights the potential of hybrid methods to extend the applicability and effectiveness of traditional techniques.

Current point cloud denoising (PCD) models optimize single networks, trying to make their parameters adaptive to each point in a large pool of point clouds. Such a denoising network paradigm neglects that different points are often corrupted by different levels of noise and they may convey different geometric structures. Thus, the intricacy of both noise and geometry poses side effects including remnant noise, wrongly-smoothed edges, and distorted shape after denoising. We propose PathNet, a path-selective PCD paradigm based on reinforcement learning (RL). Unlike existing efforts, PathNet enables dynamic selection of the most appropriate denoising path for each point, best moving it onto its underlying surface. We have two more contributions besides the proposed framework of path-selective PCD for the first time. First, to leverage geometry expertise and benefit from training data, we propose a noise- and geometry-aware reward function to train the routing agent in RL. Second, the routing agent and the denoising network are trained jointly to avoid under- and over-smoothing. Extensive experiments show promising improvements of PathNet over its competitors, in terms of the effectiveness for removing different levels of noise and preserving multi-scale surface geometries. Furthermore, PathNet generalizes itself more smoothly to real scans than cutting-edge models.

While salient object detection (SOD) on 2D images has been extensively studied, there is very little SOD work on 3D measurement surfaces. We propose an effective point transformer-based SOD network for 3D measurement point clouds, termed PSOD-Net. PSOD-Net is an encoder-decoder network that takes full advantage of transformers to model the contextual information in both multi-scale point- and scene-wise manners. In the encoder, we develop a Point Context Transformer (PCT) module to capture region contextual features at the point level; PCT contains two different transformers to excavate the relationship among points. In the decoder, we develop a Scene Context Transformer (SCT) module to learn context representations at the scene level; SCT contains both Upsampling-and-Transformer blocks and Multi-context Aggregation units to integrate the global semantic and multi-level features from the encoder into the global scene context. Experiments show clear improvements of PSOD-Net over its competitors and validate that PSOD-Net is more robust to challenging cases such as small objects, multiple objects, and objects with complex structures. Code is available at: https://github.com/ZeyongWei/PSOD-Net.

Point cloud denoising and normal estimation are two fundamental yet dependent problems in digital geometry processing. However, both are often independently researched, leading to inconsistent geometry on 3D surfaces. To address it, we propose PN-Internet, an end-to-end Point-and-Normal Interactive Network for joint point cloud denoising and normal estimation. PN-Internet leverages the geometric dependency between point positions and normals to design two interactive graph convolution networks (GCNs): a point-to-normal network and a normal-to-point network. It adopts a coarse-to-fine learning paradigm, where two GCNs are exploited to respectively perform point cloud denoising and normal estimation. The point-to-normal network improves the quality of the normals using an MLP module, while the normal-to-point network refines the point positions using a parameter-free projection module based on the constraints from the normals. In addition, we introduce a feature-aware loss function to preserve the quality of 3D shape features. Unlike most existing methods, PN-Internet takes advantage of the geometric dependency between points and normals and benefits from training data. Our experimental results demonstrate that PN-Internet achieves geometric consistency between point cloud denoising and normal estimation. Furthermore, we show significant improvements over state-of-the-art methods.

We propose GeoGCN, a novel geometric dual-domain graph convolution network for point cloud denoising (PCD). Beyond the traditional wisdom of PCD, to fully exploit the geometric information of point clouds, we define two kinds of surface normals, one is called Real Normal (RN), and the other is Virtual Normal (VN). RN preserves the local details of noisy point clouds while VN avoids the global shape shrinkage during denoising. GeoGCN is a new PCD paradigm that, 1) first regresses point positions by spatial-based GCN with the help of VNs, 2) then estimates initial RNs by performing Principal Component Analysis on the regressed points, and 3) finally regresses fine RNs by normal-based GCN. Unlike existing PCD methods, GeoGCN not only exploits two kinds of geometry expertise (i.e., RN and VN) but also benefits from training data. Experiments validate that GeoGCN outperforms SOTAs in terms of both noise-robustness and local-and-global feature preservation.

Convolution on 3D point clouds is widely researched yet far from perfect in geometric deep learning. The traditional wisdom of convolution characterises feature correspondences indistinguishably among 3D points, arising an intrinsic limitation of poor distinctive feature learning. In this article, we propose Adaptive Graph Convolution (AGConv) for wide applications of point cloud analysis. AGConv generates adaptive kernels for points according to their dynamically learned features. Compared with the solution of using fixed/isotropic kernels, AGConv improves the flexibility of point cloud convolutions, effectively and precisely capturing the diverse relations between points from different semantic parts. Unlike the popular attentional weight schemes, AGConv implements the adaptiveness inside the convolution operation instead of simply assigning different weights to the neighboring points. Extensive evaluations clearly show that our method outperforms state-of-the-arts of point cloud classification and segmentation on various benchmark datasets. Meanwhile, AGConv can flexibly serve more point cloud analysis approaches to boost their performance. To validate its flexibility and effectiveness, we explore AGConv-based paradigms of completion, denoising, upsampling, registration and circle extraction, which are comparable or even superior to their competitors.

Self-supervised learning is attracting large attention in point cloud understanding. However, exploring discriminative and transferable features still remains challenging due to their nature of irregularity. We propose a geometrically and adaptively masked auto-encoder on point clouds for self-supervised learning, termedPointGame. PointGame contains two core components: GATE and EAT. GATE stands for the geometrical and adaptive token embedding module; it not only absorbs the conventional wisdom of geometric descriptors that captures the surface shape effectively, but also exploits adaptive saliency to focus on the salient part of a point cloud. EAT stands for the external attention-based Transformer encoder with linear computational complexity, which increases the efficiency of the whole pipeline. Unlike cutting-edge unsupervised learning models, PointGame leverages geometric descriptors to perceive surface shapes and adaptively mines discriminative features from training data. PointGame showcases clear advantages over its competitors on various downstream tasks under both global and local fine-tuning strategies. The code and pre-trained models will be publicly available.