Estimating 3D information about objects from a single image is a challenging problem in computer vision due to the lack of multi-view information for depth estimation. The Transformer-based methods propagate the target's 3D center depth within its 2D bounding box to construct object-level depth labels. By treating the 2D box area as a unified entity, these methods can perform sufficient feature sampling and parsing within the aforementioned area. This rough but robust detection strategy effectively avoids the dependence of 3D detection on accurate depth estimation of the target center and a few key points nearby. However, due to the lack of effective foreground constraints, these methods struggle to ensure that sampling points are located inside the target, while exterior points lack valid depth values for supervision, which affects both detection accuracy and stability. To address this issue, we propose a Foreground-Constrained Monocular 3D Object Detector (FC-MonoDETR). First, we leverage 2D annotations to generate target segmentation masks using the Segment Anything Model (SAM), directly establishing depth supervision under foreground constraints. Second, we design an attention-based feature fusion module that utilizes contour information to refine visual features and emphasizes the role of foreground regions in depth estimation, guiding the network to focus more effectively on the foreground during holistic 3D information parsing. Finally, we model the relative depth relationships between targets and optimize the estimation of the target's center depth through a specially designed target center depth loss function. Considering the stability issues of Transformer-based methods, we recommend using a more comprehensive evaluation strategy. The sufficient migration experiments have verified the effectiveness of our constructed foreground-constrained depth supervision and feature fusion module in optimizing Transformer-based methods.

The irregular and chaotically interwoven distributions of vegetation and rock mass in natural environments pose significant challenges for vegetation filtering of rock point clouds, as existing methods struggle with inefficient contextual modeling and insufficient feature discriminability. To address these limitations, we propose a robust vegetation filtering method for rock mass scene point clouds featuring two key innovations: (1) Bidirectional Point Cloud Mamba module that adopts an alternating allocation strategy to divide the sampled superpoints into two complementary groups, and constructs optimized sequences from edge to center for each group via the Traveling Salesman Problem (TSP) algorithm to enable spatially continuous context capture while eliminating dependency on regular geometric priors; (2) Structure-based adaptive Tri-Plane feature representation includes Principal Component Analysis (PCA)-based support plane selection, projective 2D feature mapping, and learnable multi-scale aggregation. By exploiting the distribution differences of rock mass and vegetation structure information in 2D projections while emulating human visual perception mechanisms that rely on optimal viewing perspectives and different scales, this module enables more discriminative feature extraction in complex natural rock-mass scenarios. Extensive comparative and ablation experiments on real-world datasets demonstrate that our method achieves superior accuracy, robustness, and generalization, and excels in preserving intricate details compared to existing methods.

Hyperspectral image (HSI), with their rich spectral information and spatial details, have demonstrated significant potential for classification tasks in fields such as remote sensing, agriculture, and environmental monitoring. However, existing methods still exhibit limitations in feature representation, primarily manifested in insufficient contextual modeling and the inability to effectively address spectral redundancy and significant variations in spatial scales. To address these challenges, this paper proposes an enhanced MambaHSI-based framework for HSI classification, focusing on improving the representation capability of spatial-spectral features. The proposed method consists of three key innovations: (1) A hierarchical DualGroupMamba module that progressively models intra-group and inter-group spectral dependencies to enhance fine-grained spectral discrimination and global contextual awareness; (2) a lightweight Hyperspectral Channel Attention (HCA) that dynamically adjusts the importance of feature channels based on the spatial–spectral information of different bands, effectively suppressing redundant information and highlighting discriminative features. (3) a Hybrid Feature Enhancer (HFE) module that effectively represents and fuses multi-scale spatial features by extracting local texture details and perceiving the overall spatial distribution of scenes, thereby enhancing the model’s adaptability to complex spatial structures. Through a systematic evaluation on four benchmark hyperspectral datasets, the proposed method achieved an average overall classification accuracy of 95.64%, outperforming the current best method by 1.89%. The experimental results validate the superior performance of the proposed approach in enhancing the representation of spatial–spectral features. The latest logs are now available at https://github.com/Tomyaya/EFR.

The conventional borehole transient electromagnetic method (BTEM) is limited by full-space effects, resulting in considerable errors in the spatial parameters of localized anomalous bodies. To improve the spatial resolutions of the low-resistivity anomalous bodies around a borehole, a modified BTEM method, utilizing a pair of magnetic dipoles to create local magnetic monopoles, is proposed. Based on the Maxwell’s diffusion solution, the three-component analytical solution of the transient magnetic field, generated by superposing a pair of spaced and oppositely polarized magnetic dipoles, is derived. Two magnetic monopoles with opposite polarities in the axial and radial directions are created. Compared to a single magnetic dipole source, the response amplitude of the radial component excited by the magnetic monopole source is stronger. Numerical simulations and physical experiments show that the radial component is highly sensitive to the radial and axial distances and azimuthal angle of the low-resistivity anomalous body. This component detects responses at all radial azimuthal angles. The axial component can determine whether the low-resistivity body is located in front of or behind the probe, although with a limited azimuth angle detection ability, which can be supplemented by the radial azimuth angle. Herein, a spatial localization method for a single low-resistivity anomalous body in full space is proposed. This method is applied at an actual mining site to spatially locate and image hidden water hazards. It effectively depicts the distribution of low-resistivity water sources around the borehole. This study provides a novel technical approach for precisely detecting low-resistivity zones in integrated drilling and geophysical prospecting projects, which has significant theoretical significance and practical application value.

Panoramic depth estimation has become a hot topic in 3D reconstruction techniques with its omnidirectional spatial field of view. However, panoramic RGB-D datasets are difficult to obtain due to the lack of panoramic RGB-D cameras, thus limiting the practicality of supervised panoramic depth estimation. Self-supervised learning based on RGB stereo image pairs has the potential to overcome this limitation due to its low dependence on datasets. In this work, we propose the SPDET, an edge-aware self-supervised panoramic depth estimation network that combines the transformer with a spherical geometry feature. Specifically, we first introduce the panoramic geometry feature to construct our panoramic transformer and reconstruct high-quality depth maps. Furthermore, we introduce the pre-filtered depth-image-based rendering method to synthesize the novel view image for self-supervision. Meanwhile, we design an edge-aware loss function to improve the self-supervised depth estimation for panorama images. Finally, we demonstrate the effectiveness of our SPDET with a series of comparison and ablation experiments while achieving the state-of-the-art self-supervised monocular panoramic depth estimation. Our code and models are available at https://github.com/zcq15/SPDET.

Multi-view Stereo (MVS) aims to reconstruct a 3D point cloud model from multiple views. In recent years, learning-based MVS methods have received a lot of attention and achieved excellent performance compared with traditional methods. However, these methods still have apparent shortcomings, such as the accumulative error in the coarse-to-fine strategy and the inaccurate depth hypotheses based on the uniform sampling strategy. In this paper, we propose the NR-MVSNet, a coarse-to-fine structure with the depth hypotheses based on the normal consistency (DHNC) module, and the depth refinement with reliable attention (DRRA) module. Specifically, we design the DHNC module to generate more effective depth hypotheses, which collects the depth hypotheses from neighboring pixels with the same normals. As a result, the predicted depth can be smoother and more accurate, especially in texture-less and repetitive-texture regions. On the other hand, we update the initial depth map in the coarse stage by the DRRA module, which can combine attentional reference features and cost volume features to improve the depth estimation accuracy in the coarse stage and address the accumulative error problem. Finally, we conduct a series of experiments on the DTU, BlendedMVS, Tanks & Temples, and ETH3D datasets. The experimental results demonstrate the efficiency and robustness of our NR-MVSNet compared with the state-of-the-art methods. Our implementation is available at https://github.com/wdkyh/NR-MVSNet.

Depth estimation is a crucial step for 3D reconstruction with panorama images in recent years. Panorama images maintain the complete spatial information but introduce distortion with equirectangular projection. In this paper, we propose an ACDNet based on the adaptively combined dilated convolution to predict the dense depth map for a monocular panoramic image. Specifically, we combine the convolution kernels with different dilations to extend the receptive field in the equirectangular projection. Meanwhile, we introduce an adaptive channel-wise fusion module to summarize the feature maps and get diverse attention areas in the receptive field along the channels. Due to the utilization of channel-wise attention in constructing the adaptive channel-wise fusion module, the network can capture and leverage the cross-channel contextual information efficiently. Finally, we conduct depth estimation experiments on three datasets (both virtual and real-world) and the experimental results demonstrate that our proposed ACDNet substantially outperforms the current state-of-the-art (SOTA) methods. Our codes and model parameters are accessed in https://github.com/zcq15/ACDNet.

In recent years, supervised or unsupervised learning-based MVS methods achieved excellent performance compared with traditional methods. However, these methods only use the probability volume computed by cost volume regularization to predict reference depths and this manner cannot mine enough information from the probability volume. Furthermore, the unsupervised methods usually try to use two-step or additional inputs for training which make the procedure more complicated. In this paper, we propose the DS-MVSNet, an end-to-end unsupervised MVS structure with the source depths synthesis. To mine the information in probability volume, we creatively synthesize the source depths by splattering the probability volume and depth hypotheses to source views. Meanwhile, we propose the adaptive Gaussian sampling and improved adaptive bins sampling approach that improve the depths hypotheses accuracy. On the other hand, we utilize the source depths to render the reference images and propose depth consistency loss and depth smoothness loss. These can provide additional guidance according to photometric and geometric consistency in different views without additional inputs. Finally, we conduct a series of experiments on the DTU dataset and Tanks $&$ Temples dataset that demonstrate the efficiency and robustness of our DS-MVSNet compared with the state-of-the-art methods.

Registration will directly affect the quality of overall rock-mass point cloud, which is the basis of 3-D reconstruction for rock mass. Advanced methods establish correspondence by extracting various features that remain unchanged. Although these methods have made great progress, they analyze the local characteristics of each sample point, which leads to be inefficient. In this article, we select registration interesting points from feature lines that were extracted based on supervoxel and innovatively introduce the “clustering, primary matching, and coarse registration” strategy, which effectively reduces the complexity of calculating the corresponding relationship during point cloud registration. Finally, the iterative closest point (ICP) algorithm is used to optimize the result of coarse registration. By selecting registration interesting points from the extracted feature lines, the proposed method inherits the robustness of feature lines to noise, initial position, and so on. The experimental results prove that the coarse registration and refined registration results of the proposed method both have high accuracy and efficiency.

Obtaining complete point cloud data is the basis of rock surface segmentation and related rock-mass numerical simulation. The existing rock-mass point cloud registration methods usually extract point features as the key information for registration. However, the calculation results of point features may be affected by many factors such as data integrity, point density, and noise, which limits the application of existing algorithms in some complex rock scenes (complex collection conditions and complex surface structures). In this article, we propose to divide the rock-mass registration task into two stages: global matching and local matching. During global matching, we extract structure-level features (interrelationships between planes) and shape features (point distribution information in a specific region) instead of point features as the basis for establishing preliminary correspondence between point clouds, achieving robust and efficient region-to-region matching. In the local matching stage, the method based on feature point extraction and matching is proposed to establish accurate point-to-point correspondences in the local region, thus effectively solving the influence of the error of structure-level feature matching on the registration accuracy. In this article, the registration accuracy and efficiency of our method are fully validated by using both repository datasets and real-scene datasets. The robustness of the method is also demonstrated under various conditions. The experimental results show that the root-mean-square error of this method is less than 0.05 m when dealing with mountain data with a length greater than 200 m, which is obviously better than the existing best method.

Existing 3-D object extraction methods on terrestrial laser point clouds are further developed through filtering and labeling. However, such predefined features are heuristically designed to process generic object point clouds. Thus, existing abilities are insufficient to handle specific rock-mass point clouds. Given the complexity and diversity of terrestrial environments, the effective removal of vegetation points from rock-mass point clouds is particularly challenging. To address such problems, this study presents a novel approach for 3-D rock-mass point clouds labeling by using convolutional feature learning based on distribution priors with multiple scales and views. First, to extract discriminative features of each point for classification, we propose novel multiview supporting planes to analyze the spatial distribution and structure of its neighboring points for each category. Second, we define the multiscale spatial distribution matrix on a grid representation (e.g., the number of points projected into each cell). Last, the statistical information of points is nonlinearly combined and hierarchically compressed to generate a compact and effective convolutional feature representation for classification. The effectiveness of the proposed method is evaluated via experiments on rock-mass point clouds from different scenes. Compared with existing extraction approaches, experimental results indicate the superiority of the proposed method in terms of the precision and recall.

The surfaces of rock masses are arbitrary and complex. Moreover, the point clouds of rock-mass surfaces acquired via terrestrial laser scanning typically span large distances and have high resolutions. These characteristics cause difficulties in registration between scans. To address these difficulties, an efficient method using$n$-point complete graphs is proposed. To handle massive point clouds, a step-by-step strategy is adopted to reduce the number of points involved in the computation. First, the Gaussian curvature of each point of the initial data is estimated, and points with low Gaussian curvatures are filtered out such that only the interesting points are preserved. Second, these interesting points are clustered, and the centroid of each cluster is calculated. Finally, a descriptor is built from the$n$-point complete graph formed by each centroid and its$n-1$nearest neighbors. By matching the descriptors generated from two point clouds, corresponding point pairs can be obtained, thus achieving alignment. In addition, this strategy inherently incorporates denoising, outlier handling, and filtration, thereby endowing the method with strong adaptability to various conditions without incurring any additional cost. Experiments on data sets with varying degrees of outliers, noise and overlap were conducted to demonstrate the robustness of the proposed method. The results show that, with point span$r~\approx ~1$cm, the output root mean square error is around 0.5 cm, which is comparable with that of the Iterative Closest Point algorithm. A runtime analysis shows that the total processing time of the proposed method grows nearly linearly with increasing data size.