Triangular Mesh Data Research Articles

A method for assessing guide layout and error on implant accuracy

Functional and esthetic results require accurate implant placement. We aimed to develop a predictive method for assessing guide layout and error on implant accuracy. A mathematical model for position error analysis was constructed based on triangular mesh data. This model examines the relationship between the spatial shifts of multiple surfaces and the spatial shifts of specific points. It involves encasing these surfaces in a cuboid bounding box and expressing them in a local coordinate system. The influence of positioning surface error and layout of surgical guide were researched with a simulation test. The result shows that error in the implant site position is directly related to the error in the guide locating surface under the same layout. When the guide locating surface layout varies, as the length, width, and height of the minimum cuboid envelope increase, the maximum deviation in the implant site position decreases.

A detection method for road network interchanges with the MeshCNN based on Delaunay triangulation

ABSTRACT Due to their unstructured characteristics, mature convolutional neural network (CNN) models often have difficulty performing spatial analysis with vector data. Current studies used graph neural network (GCN) models to address this problem. However, the definition of cognition factors involves uncertainties, making it challenging to accurately and comprehensively define these factors. In this paper, the road interchange detection task is taken as an example to introduce the MeshCNN, a deep learning model based on triangular mesh data, aiming to provide a new solution for spatial analysis of vector data. A triangular edge classification model is first trained with simple input features. Then, interchanges are detected based on the classification results with an adaptive method. Experiments were conducted on real-world road network data from four cities. The results reveal that the proposed method outperformed the existing methods with precision and recall rate of 89.36% and 79.25% for interchange detection on the total datasets. Furthermore, our proposed method can also detect interchanges in other regions more easily than the GCN method.

Camera Path Generation for Triangular Mesh Using Toroidal Patches

Triangular mesh data structures are principal in computer graphics, serving as the foundation for many 3D models. To effectively utilize these 3D models across diverse industries, it is important to understand the model’s overall shape and geometric features thoroughly. In this work, we introduce a novel method for generating camera paths that emphasize the model’s local geometric characteristics. This method uses a toroidal patch-based spatial data structure, approximating the mesh’s faces within a predetermined tolerance ϵ, encapsulating their geometric intricacies. This facilitates the determination of the camera position and gaze path, ensuring the mesh’s key characteristics are captured. During the path construction, we create a bounding cylinder for the mesh, project the mesh’s faces and associated toroidal patches onto the cylinder’s lateral surface, and sequentially select grids of the cylinder containing the highest number of toroidal patches as we traverse the lateral surface. The centers of the selected grids are used as control points for a periodic B-spline curve, which serves as our foundational path. After initial curve generation, we generated camera position and gaze path from the curve by multiplying factors to ensure a uniform camera amplitude. We applied our method to ten triangular mesh models, demonstrating its effectiveness and adaptability across various mesh configurations.

Automated Process Planning System for End-Milling Operation by CAD Model in STL Format

A method for extracting the machining region from a 3D CAD model in Standard Triangulated Language (STL) format and automatically generating a tool path is proposed. First, a method is proposed for extracting the machining region and obtaining the geometrical features such as a convex or concave shape from only the 3D CAD model in STL format. The STL format uses only triangular mesh data and drops all information, which is necessary for extracting the removal volume for the machining and geometrical characteristics. Furthermore, the triangular mesh size is non-uniform. A contour line model is proposed in which the product model is minutely divided on the plane along any one axial direction and is represented by points at intervals below the indicated resolution obtained from the contour line of the cross section of the product. Subsequently, a method is proposed to determine the machining conditions for each extracted machining region and automatically generate a tool path according to the geometrical features of the machining region obtained. A machining experiment was conducted to validate the effectiveness of the proposed method. As a result of the machining experiment, it was confirmed that the tool path automatically generated from the 3D CAD model in STL format can be machined without any problems and with a practical level of accuracy.

Many-Objective Deployment Optimization for a Drone-Assisted Camera Network

Drone-assisted camera networks can be used in many applications. However, different application requirements lead to different deployment scenarios. In this paper, based on a 3D terrain environment represented by triangular mesh data, a many-objective optimization model for the deployment of multiple onboard cameras is constructed. We propose an improved version of the constrained two-archive evolutionary algorithm. A selection operator based on Gaussian process regression is used for enhancement. Additionally, we quantize the polynomial mutation operator. The improved algorithm is applied to optimize drone-assisted camera deployment, and the experimental results show that the improved algorithm is superior to state-of-the-art algorithms.

Conformal coverage of liver tumors by the thermal coagulation zone in 2450-MHz microwave ablation

Purpose: To optimize treatment schemes using 2450-MHz microwave ablation (MWA), a novel conformal coverage method based on bipolar-angle mapping is proposed that determines whether a liver tumor is completely encompassed by thermal coagulation zones.Materials and methods: Firstly, three-dimensional (3-D) triangular mesh data of liver tumors were reconstructed from clinical computed tomography (CT) slices using the Marching cubes (MC) algorithm. Secondly, characterization models of thermal coagulation zones were established based on finite element simulation results of 40, 45, 50, 55, and 60 W ablations. Finally, coagulation zone models and tumor surface data were mapped and fused on a two-dimensional (2-D) plane to achieve conformal coverage of liver tumors by comparing the corresponding polar radii.Results: Optimal parameters for ablation treatment of liver tumors were efficiently obtained with the proposed conformal coverage method. Fifteen liver tumors were obtained with maximal diameters of 12.329–78.612 mm (mean ± standard deviation, 39.094 ± 19.447 mm). The insertion positions and orientations of the MWA antenna were determined based on 3-D reconstruction results of these tumors. The ablation patterns and durations of tumors were planned according to the minimum mean standard deviations between the ablative margin and tumor surface.Conclusion: The proposed method can be applied to computer-assisted MWA treatment planning of liver tumors, and is expected to guide clinical procedures in future.

INDOOR SPATIAL DATA CONSTRUCTION FROM TRIANGLE MESH

Abstract. The 3D triangle mesh is widely used to represent indoor space. One of widely used methods of generating 3D triangle mesh data of indoor space is the construction from the point cloud collected using LIDAR. However, there are many problems in using generated triangle mesh data as a geometric representation of the indoor space. First, the number of triangles forming the triangle mesh is very large, which results in a bottleneck of the performance for storage and management. Second, no consideration on the properties of indoor space has been done by the previous work on mesh simplification for indoor geometric representation. Third, there is no research to construct indoor spatial standard data from triangle mesh data. For resolving these problems, we propose the a method for generating triangular mesh data for indoor geometric representation based in the observations mentioned above. First this method removes unnecessary objects and reduces the number of surfaces from the original fine-grained triangular mesh data using the properties of indoor space. Second, it also produces indoor geometric data in IndoorGML – an OGC standard for indoor spatial data model. In experimental studies, we present a case study of indoor triangle mesh data from real world and compare results with raw data.

Study on digital teeth selection and virtual teeth arrangement for complete denture

Background and objectiveIn dentistry, the complete denture is a conventional treatment for edentulous patients. The computer-aided design and computer-aided manufacturing (CAD/CAM) has been applied on the digital complete denture which is developed rapidly. Tooth selection and arrangement is one of the most important parts in digital complete denture. In this paper, we propose a new method of personalized teeth arrangement. MethodsThis paper presents a method of arranging teeth virtually for a complete denture. First, scan and extract the feature points of the 3D triangular mesh data of artificial teeth (PLY format), then establish a tooth selection system. Second, scan and mark the anatomic characteristics of the maxillary and mandibular cast surfaces, such as facial midline, the curve of the arches. With the enter information, the study calculates the common arrangement lines of artificial teeth. Third, select the preferred artificial teeth and automatically arrange them virtually in the correct position by using our own software. After that, design the gingival part of the dentures on the basic of the arranged teeth on the screen and then fabricated it by using Computerized Numerical Control (CNC) technology, Rapid Prototyping (RP) technology or 3D printer technology. Finally, select artificial teeth were embedded in wax rims. ResultsThis system can choose artificial teeth reasonably and the teeth placement can meet the dentist's request to a certain extent, whereas all the operations are based on the medical principles. ConclusionsThe study performed here involves computer sciences, medicine, and dentistry, a teeth selection system was proposed and virtual teeth arrangement was described. This study has the capacity of helping operators to select teeth, which improved the accuracy of tooth arrangement, and customized complete denture.

基于Geomagic spark的手扶式插秧机变速箱箱体重构

变速箱是插秧机的核心部件之一。本文针对插秧机变速箱箱体改造，应用逆向工程软件Geomagic spark来重构变速箱箱体，并对其进行优化设计。首先，利用手持式激光扫描仪对变速箱箱体进行扫描，获取三维点云数据；再利用正逆向混合软件Geomagic spark对扫描得到的点云数据进行三角形网格模型重建；依据三角形网格数据重构变速箱箱体的三维几何模型。根据得到的三维几何模型对模型进行优化，最后在SolidWorks Simulation中进行有限元分析，为箱体的优化设计提供了理论基础。利用逆向工程技术对插秧机变速箱箱体进行优化，可以缩短设计周期，降低设计成本。 The gearbox is one of the core components of the transplanter. In this paper, according to the transformation of the gearbox body, Geomagic spark, a reverse engineering software, is applied to reconstruct the gearbox body, and then the optimization design is made on it. Firstly, the gearbox is scanned by hand-held laser scanner, and the 3D point cloud data is obtained. Then, the point cloud is reconstructed by using the Geomagic spark software. The three dimensional geometric model of transmission box is reconstructed by using the triangular mesh data. According to the obtained three dimensional geometric models, the model is optimized. Finally, the finite element analysis is carried out in Solid-Works Simulation, which provides a theoretical basis for the optimization design of the box. Using reverse engineering technology to optimize the transplanter gearbox, it can shorten the design cycle and reduce design costs.

Development of a surface-based virtual dental sculpting simulator with multimodal feedback

This paper presents a surface-based virtual dental sculpting simulator based on sensory modalities like visual, auditory and haptic sensation. The simulator can be used to perform different dental procedures such as grinding, drilling, or surface scrubbing, and gain experience of using various virtual dental tools of different shapes. The surface-based dental model, which is extracted from a commercial 3D dental laser scanner, is used for simulating sculpting processes at less memory cost. Large amount of triangular mesh data is contained in scanned models; therefore, a model reduction algorithm is proposed for large triangular mesh data. For the computation of repulsive force feedback, a spring-damper force model with a force filter is used. Vertex deformation method is implemented along with an enhanced bi-tri subdivision method of triangles to perform precision sculpting simulation. In order to make the mesh regular, a number of mesh refinement algorithms are performed. Finally, considering the fidelity, stability, computer efficiency, and update rate of the haptic display, it can be concluded that these multimodal realities based virtual system can generate stable simulation of material removal from a human tooth model with realistic auditory, visual, and force sensations.

CAD Software Development for the Continuous Flexible Forming Process

The software for the continuous flexible forming process was developed using Visual C++ platform. It can directly read the triangular mesh data of the CAD model. The three-dimensional model was reconstructed rapidly by using the core function of the OpenGL. Moreover, the mathematical model of adjusting the flexible rolls and the longitudinal curvature were established by this software. Using these mathematical descriptions the simulation of the continuous flexible forming process can be finished from the viewpoint of geometry.

Performance characterization of microtomography with complementary metal-oxide-semiconductor detectors for computer-aided defect inspection

We developed a computer-aided defect inspection system based on computed tomography (CT). The system consists of a homemade small cone-beam CT (CBCT) system and a graphical toolbox, which is used to extract a computer-aided design (CAD) model from the CT data. In the small CBCT system, the x-ray imaging detector is based on a complementary metal-oxide-semiconductor photodiode array in conjunction with a scintillator. Imaging performance of the detector was evaluated in terms of modulation-transfer function, noise-power spectrum, and detective quantum efficiency. The tomographic imaging performance of the small CBCT system was evaluated in terms of signal-to-noise ratio and contrast-to-noise ratio. The graphical toolbox to support defect inspection incorporates various functional tools such as volume rendering, segmentation, triangular-mesh data generation, and data reduction. All the tools have been integrated in a graphical-user interface form. The developed system can provide rapid visual inspection as well as quantitative evaluation of defects by comparing the extracted CAD file with the original file, if available, of an object. The performance of the developed system is demonstrated with experimental CT volume data.

Boundary-trimmed 3D triangular mesh segmentation based on iterative merging strategy

This paper presents a segmentation algorithm for 3D triangular mesh data. The proposed algorithm uses iterative merging of adjacent triangle pairs based on their orientations. The oversegmented regions are merged again in an iterative region merging process. Finally, the noisy boundaries of each region are refined. The boundaries of each region contain perceptually important geometric information of the entire mesh model. According to the purpose of the segmentation, the proposed mesh-segmentation algorithm supports various types of segmentation by controlling parameters.