3维Douglas-Peucker算法及其在DEM自动综合中的应用研究

在分析2维Douglas-Peucker算法原理实质的基础上,提出3维Douglas-Peucker算法,并将此法应用到对DEM的基础———3维离散点的自动综合上。采用计算机程序对新算法进行的验证,初步结果表明该算法能较好地筛选出DEM整体及局部范围的地貌特征点,其计算效率也较令人满意。

Three-dimensional(3D)parametric measurements of individual gravels in the Gobi region using point cloud technique

Gobi spans a large area of China,surpassing the combined expanse of mobile dunes and semi-fixed dunes.Its presence significantly influences the movement of sand and dust.However,the complex origins and diverse materials constituting the Gobi result in notable differences in saltation processes across various Gobi surfaces.It is challenging to describe these processes according to a uniform morphology.Therefore,it becomes imperative to articulate surface characteristics through parameters such as the three-dimensional(3D)size and shape of gravel.Collecting morphology information for Gobi gravels is essential for studying its genesis and sand saltation.To enhance the efficiency and information yield of gravel parameter measurements,this study conducted field experiments in the Gobi region across Dunhuang City,Guazhou County,and Yumen City(administrated by Jiuquan City),Gansu Province,China in March 2023.A research framework and methodology for measuring 3D parameters of gravel using point cloud were developed,alongside improved calculation formulas for 3D parameters including gravel grain size,volume,flatness,roundness,sphericity,and equivalent grain size.Leveraging multi-view geometry technology for 3D reconstruction allowed for establishing an optimal data acquisition scheme characterized by high point cloud reconstruction efficiency and clear quality.Additionally,the proposed methodology incorporated point cloud clustering,segmentation,and filtering techniques to isolate individual gravel point clouds.Advanced point cloud algorithms,including the Oriented Bounding Box(OBB),point cloud slicing method,and point cloud triangulation,were then deployed to calculate the 3D parameters of individual gravels.These systematic processes allow precise and detailed characterization of individual gravels.For gravel grain size and volume,the correlation coefficients between point cloud and manual measurements all exceeded 0.9000,confirming the feasibility of the proposed methodology for measuring 3D parameters of individual gravels.The proposed workflow yields accurate calculations of relevant parameters for Gobi gravels,providing essential data support for subsequent studies on Gobi environments.

A New Three-Dimensional(3D)Printing Prepress Algorithm for Simulation of Planned Surgery for Congenital Heart Disease

Background:Three-dimensional printing technology may become a key factor in transforming clinical practice and in significant improvement of treatment outcomes.The introduction of this technique into pediatric cardiac surgery will allow us to study features of the anatomy and spatial relations of a defect and to simulate the optimal surgical repair on a printed model in every individual case.Methods:We performed the prospective cohort study which included 29 children with congenital heart defects.The hearts and the great vessels were modeled and printed out.Measurements of the same cardiac areas were taken in the same planes and points at multislice computed tomography images(group 1)and on printed 3D models of the hearts(group 2).Pre-printing treatment of the multislice computed tomography data and 3D model preparation were performed according to a newly developed algorithm.Results:The measurements taken on the 3D-printed cardiac models and the tomographic images did not differ significantly,which allowed us to conclude that the models were highly accurate and informative.The new algorithm greatly simplifies and speeds up the preparation of a 3D model for printing,while maintaining high accuracy and level of detail.Conclusions:The 3D-printed models provide an accurate preoperative assessment of the anatomy of a defect in each case.The new algorithm has several important advantages over other available programs.They enable the development of customized preliminary plans for surgical repair of each specific complex congenital heart disease,predict possible issues,determine the optimal surgical tactics,and significantly improve surgical outcomes.

Improvement of Binocular Reconstruction Algorithm for Measuring 3D Pavement Texture Using a Single Laser Line Scanning Constraint

The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function.To form dense mandatory constraints and improve matching accuracy,the traditional binocular reconstruction technology was improved threefold.First,a single moving laser line was introduced to carry out global scanning constraints on the target,which would well overcome the difficulty of installing and recognizing excessive laser lines.Second,four kinds of improved algorithms,namely,disparity replacement,superposition synthesis,subregion segmentation,and subregion segmentation centroid enhancement,were established based on different constraint mechanism.Last,the improved binocular reconstruction test device was developed to realize the dual functions of 3D texture measurement and precision self-evaluation.Results show that compared with traditional algorithms,the introduction of a single laser line scanning constraint is helpful in improving the measurement’s accuracy.Among various improved algorithms,the improvement effect of the subregion segmentation centroid enhancement method is the best.It has a good effect on both overall measurement and single pointmeasurement,which can be considered to be used in pavement function evaluation.

再论三维Douglas-Peucker算法及其在DEM综合中的应用

相对于笔者在已发表论文中所提出的一般性方法,本文在算法上有了进一步的改善或扩展。结果表明,这些措施在保证综合效果的前提下,可以大大提高DEM的综合速度,从而为海量DEM数据的全局动态式综合提供了现实的可能性。

基于改进蝴蝶优化算法的无人机3-D航迹规划方法

针对基本蝴蝶优化算法(Butterfly optimization algorithm,BOA)在进行无人机(Unmanned aerial vehicle,UAV)三维航迹规划时存在的搜索速度慢、搜索精度低以及易陷入局部最优等问题,提出一种改进的蝴蝶优化算法(Improved butterfly optimization algorithm,IBOA)。在全局搜索阶段提出对数自适应惯性权重策略和动态更新调节策略,提高了算法全局搜索能力和搜索精度。同时,在局部搜索阶段,提出一种动态概率余弦选择策略,增加位置更新多样性,避免陷入局部最优。首先,为检验改进算法与基本算法的寻优性能,在部分标准多元函数上进行仿真对比。对比结果表明,改进算法对复杂函数具有较强的寻优能力,能在更短时间内找到全局最优解。然后,在二维路径规划仿真中对比了改进算法与PSO算法性能,从对比结果看,IBOA具有更优的规划效果。接着,利用山峰模拟函数对UAV三维航迹规划进行建模,将改进算法应用到航迹规划中,利用MATLAB仿真对比了不同复杂度环境下的航迹规划效果。仿真实验表明:相同实验条件下,该优化算法较BOA综合适应度值减小21.9%,具有搜索速度快、搜索精度高等优点,能够有效地指导UAV在三维环境中完成自主导航避障任务。

Structural plane recognition from three-dimensional laser scanning points using an improved region-growing algorithm based on the robust randomized Hough transform

The staggered distribution of joints and fissures in space constitutes the weak part of any rock mass.The identification of rock mass structural planes and the extraction of characteristic parameters are the basis of rock-mass integrity evaluation,which is very important for analysis of slope stability.The laser scanning technique can be used to acquire the coordinate information pertaining to each point of the structural plane,but large amount of point cloud data,uneven density distribution,and noise point interference make the identification efficiency and accuracy of different types of structural planes limited by point cloud data analysis technology.A new point cloud identification and segmentation algorithm for rock mass structural surfaces is proposed.Based on the distribution states of the original point cloud in different neighborhoods in space,the point clouds are characterized by multi-dimensional eigenvalues and calculated by the robust randomized Hough transform(RRHT).The normal vector difference and the final eigenvalue are proposed for characteristic distinction,and the identification of rock mass structural surfaces is completed through regional growth,which strengthens the difference expression of point clouds.In addition,nearest Voxel downsampling is also introduced in the RRHT calculation,which further reduces the number of sources of neighborhood noises,thereby improving the accuracy and stability of the calculation.The advantages of the method have been verified by laboratory models.The results showed that the proposed method can better achieve the segmentation and statistics of structural planes with interfaces and sharp boundaries.The method works well in the identification of joints,fissures,and other structural planes on Mangshezhai slope in the Three Gorges Reservoir area,China.It can provide a stable and effective technique for the identification and segmentation of rock mass structural planes,which is beneficial in engineering practice.

Using MC Algorithm to Implement 3D Image Reconstruction for Yunnan Weather Radar Data

3D image reconstruction for weather radar data can not only help the weatherman to improve the forecast efficiency and accuracy, but also help people to understand the weather conditions easily and quickly. Marching Cubes (MC) algorithm in the surface rendering has more excellent applicability in 3D reconstruction for the slice images;it may shorten the time to find and calculate the isosurface from raw volume data, reflect the shape structure more accurately. In this paper, we discuss a method to reconstruct the 3D weather cloud image by using the proposed Cube Weighting Interpolation (CWI) and MC algorithm. Firstly, we detail the steps of CWI, apply it to project the raw radar data into the cubes and obtain the equally spaced cloud slice images, then employ MC algorithm to draw the isosurface. Some experiments show that our method has a good effect and simple operation, which may provide an intuitive and effective reference for realizing the 3D surface reconstruction and meteorological image stereo visualization.

Optimized air-ground data fusion method for mine slope modeling

Refined 3D modeling of mine slopes is pivotal for precise prediction of geological hazards.Aiming at the inadequacy of existing single modeling methods in comprehensively representing the overall and localized characteristics of mining slopes,this study introduces a new method that fuses model data from Unmanned aerial vehicles(UAV)tilt photogrammetry and 3D laser scanning through a data alignment algorithm based on control points.First,the mini batch K-Medoids algorithm is utilized to cluster the point cloud data from ground 3D laser scanning.Then,the elbow rule is applied to determine the optimal cluster number(K0),and the feature points are extracted.Next,the nearest neighbor point algorithm is employed to match the feature points obtained from UAV tilt photogrammetry,and the internal point coordinates are adjusted through the distanceweighted average to construct a 3D model.Finally,by integrating an engineering case study,the K0 value is determined to be 8,with a matching accuracy between the two model datasets ranging from 0.0669 to 1.0373 mm.Therefore,compared with the modeling method utilizing K-medoids clustering algorithm,the new modeling method significantly enhances the computational efficiency,the accuracy of selecting the optimal number of feature points in 3D laser scanning,and the precision of the 3D model derived from UAV tilt photogrammetry.This method provides a research foundation for constructing mine slope model.

A New 3D Wireless Directional Sensing Model and Coverage Enhancement Algorithm

Coverage control for each sensor is based on a 2D directional sensing model in directional sensor networks conventionally. But the 2D model cannot accurately characterize the real environment. In order to solve this problem,a new 3D directional sensor model and coverage enhancement algorithm is proposed. We can adjust the pitch angle and deviation angle to enhance the coverage rate. And the coverage enhancement algorithm is based on an improved gravitational search algorithm. In this paper the two improved strategies of GSA are directional mutation strategy and individual evolution strategy. A set of simulations show that our coverage enhancement algorithm has a good performance to improve the coverage rate of the wireless directional sensor network on different number of nodes,different virtual angles and different sensing radius.

Fragile Watermarking of 3D Models Using Genetic Algorithms

This paper describes a novel algorithm for fragile watermarking of 3D models. Fragile watermarking requires detection of even minute intentional changes to the 3D model along with the location of the change. This poses a challenge since inserting random amount of watermark in all the vertices of the model would generally introduce perceptible distortion. The proposed algorithm overcomes this challenge by using genetic algorithm to modify every vertex location in the model so that there is no perceptible distortion. Various experimental results are used to justify the choice of the genetic algorithm design parameters. Experimental results also indicate that the proposed algorithm can accurately detect location of any mesh modification.

Research on a bifurcation location algorithm of a drainage tube based on 3D medical images

Based on patient computerized tomography data,we segmented a region containing an intracranial hematoma using the threshold method and reconstructed the 3D hematoma model.To improve the efficiency and accuracy of identifying puncture points,a point-cloud search arithmetic method for modified adaptive weighted particle swarm optimization is proposed and used for optimal external axis extraction.According to the characteristics of the multitube drainage tube and the clinical needs of puncture for intracranial hematoma removal,the proposed algorithm can provide an optimal route for a drainage tube for the hematoma,the precise position of the puncture point,and preoperative planning information,which have considerable instructional significance for clinicians.

A Study on Parallel Computation Based on 3D Forward Algorithm of Gravity

Interpretation of geophysical material is the prospecting method. Interpretation of Gravity-megnetic data is based on data processing and inversion. When the grid is divided into several million cells, the computing task is heavy and time-consuming. In order to increase efficiency of the 3D forward modeling, the paper will adopt MPI parallel algorithm and the several processes will deal with data in the method. Finally, we can gather the result. Through comparing the result of sequence algorithm with the result of MPI parallel algorithm, we can see the result is the same. When the number of processes is 2 to 8, the speed-up ratio is 1.97 to 5. The MPI parallel algorithm is very efficient.

基于改进3D SPIHT的MRI序列图像压缩方法

目的研究一种有效的MRI序列图像压缩方法。方法以2组不同数量、不同层厚的MRI序列图像为例,针对3D SPIHT算法运算复杂度,在对D型、L型表项重复判断的不足上,提出了一种改进的3DSPIHT方法;同时,根据MRI序列图像的相关性特点,提出了分组编/解码的方法,结合3D小波变换和应用改进的3D SPIHT方法,实现了MRI序列图像压缩。结果分组结合改进3D SPIHT方法与2DSPIHT,3D SPIHT相比,能够得到较好重构图像,同时,峰值信噪比(PSNR)提高了1～8 dB左右。结论在相同码率下,分组结合改进3D SPIHT的方法提高了PSNR和图像恢复质量,可以更好地解决大量MRI序列图像存储与传输问题。

基于拓扑结构不变性的3D并行细化算法及其应用

目的双距离场算法提取的骨架居中性不佳,并且算法复杂度高,实时性差。本文提出一种基于拓扑结构不变性的3D细化算法以提取肺气管的骨架。方法首先介绍了基于双距离场和拓扑结构不变性两种算法的基本原理,然后通过对欧拉特性不变性的证明,利用欧拉特性表查询来计算欧拉值,并计算26临域的连通度。利用欧拉特性值和连通度来保证拓扑结构,定义了一种拓扑结构不变的简单点,用并行的细化策略,快速获取单像素宽、连通的骨架中心线。结果将此算法应用于肺气管快速提取骨架中心线,利用已经分割出的高精度肺部气道树来提取骨架中心线。结论基于拓扑结构不变性的3D并行细化算法与基于距离场的骨架提取算法相比得到更光滑、居中性更好的骨架,并且鲁棒性好,对噪声不敏感。

考虑打印件排布的3D打印批次规划

针对3D打印批次规划问题,提出一种考虑打印件排布的3D打印批次规划方法。根据3D打印工艺特点,批次规划目标设定为总打印批次及各批次内打印件高度差值最小化。采用顺序编码方式对打印件进行编号,由全部打印件编号组成的整数序列构成问题的可行解集。解码时根据编码顺序将打印件排布于打印机工作台面,当前台面再无法排入时开始下一打印批次排布,从而得到打印批次方案及优化目标函数值。通过预先求得各打印件水平面投影形状的最小包络矩形,将二维形状排布问题简化为矩形排布问题。采用最低水平线法和Bottom-Left规则进行矩形排布,排布过程中重复寻找并更新已排件区域最高轮廓线中的最低水平线段。使用遗传算法搜索问题的最优解,通过算例验证了所提方法的有效性。

一种改进了的AABB算法在3D场景少儿益智系统中的应用

碰撞检测是三维系统中实现系统角色真实感物理运动的主要算法。通过对碰撞检测AABB算法深入研究,针对碰撞检测AABB算法的运算量大、紧密性差的问题,利用BSP树剖分法和相交叉检测算法对其做了改进。并将其应用于3D场景少儿益智系统中,经实验分析,改进的碰撞检测算法能有效地减少了系统运算次数,提高了系统的运行速度。

基于鸟群算法的3D威亚系统自抗扰控制器的参数优化

针对3D舞台威亚系统自抗扰控制器(ADRC)参数多且难以整定的问题,将鸟群算法(BSA)引入其中对自抗扰控制器的参数进行了优化研究.首先根据自抗扰控制"抗扰范式"的思想,建立了3D舞台威亚系统单点吊机的"鱼骨+鱼刺"模型;接着结合3D舞台威亚的运行性能及ADRC的特质,分析确定了ADRC需优化整定的参数,并基于智能优化算法BSA对ADRC的参数进行了优化整定.仿真结果表明,BSA不仅能克服粒子群算法使ADRC参数易陷入局部最优的缺点,而且运算简单高效且易于实现,经BSA优化后的ADRC改善了3D舞台威亚单点吊机运行性能与鲁棒性,为威亚的同步控制提供了保障.

通用3D模型文件格式和算法的研究及其OpenGL实现

在探讨计算机图形学的几何造型理论基础上,提出了一种通用的3D模型文件格式(G3D)。这种采用流形三角形网格的3D模型在数学形式上是合式的,这种3D文件格式是开放的,具有可扩展性和连续的LOD能力,进一步可作交互显示、基于刚体的动画和CPM传输。然后,分析了几种典型的LOD算法,并采用OpenGL的图素构造法和交互式动画编程加以实现。最后,还探讨了CPM压缩格式定义。对自定义的三维电子文档处理、重用三维内容、Web上可视化等应用研究有很好的参考价值。