地质结构重叠域的限定Delaunay三角剖分研究

在石油储量分析的三维地质建模中出现了重叠域,需要采用特殊处理使之能应用通常的三角网格剖分算法,通过引入桥边和相交环线的概念,提出了区域子分和联动剖分算法,为重叠域的限定Delaunay三角剖分给出了一种工程处理方法,并给出了该方法对三维地质建模中逆断层剖分的实例．该方法在机械零件的复杂裂纹区应力分析、异质结构中含非流形界面的有限元分析等领域也有参考价值．     

车身冲压模型腔表面四边形网格的局部粗化

给定一车身冲压模型腔表面上结构化的四边形网格,通过单元合并对网格进行自动的粗化,其目的在于简化冲压仿真模型,提高仿真计算速度,首先,根据单元节点曲率半径的分布,搜寻出满足单元合并条件的初始四边形区域,接头,判断初始合交区域的边界过渡条件,最后,进行单合并,冲压成型仿真应用实例证明,文中算法既提高了仿真速度,又保持了仿真精度,该算法可以推广到任意曲面结构化四边形网格的局部粗化问题。     

不规则三维网格纹理映射的均匀化

采用单一纹理对不规则三维网格进行纹理映射,常常使网格密集处映射不足;而采用纹理地图集方法又使映射过程变得复杂。因此文章提出一种新的方法:通过离散保角变换方法,先将三维网格无遮挡地映射到平面正方形中,随后通过一种离散均匀面积变换方法,使其平面网格较均匀地分布,然后求得其纹理坐标,从而有效实现不规则三维网格的纹理映射。该方法算法快速、稳定,纹理映射均匀化效果良好。     

基于距离场的三维模型网格重建

根据任意亏格和任意边界的3D网格模型,给出一种网格重建算法。该算法通过对原始网格进行一系列自适应的局部修改操作,改进网格中三角形的质量和顶点位置分布。为减少优化过程中误差的累积,提出基于距离场的算法将新生成的顶点保留到原始网格曲面上,该算法实现简单,不需要复杂的全局参数化操作。实验结果表明,该算法有效、快速、稳定。     

任意三角形网格的基于二元四次箱样条分片C1曲面

提出一种以任意三角剖分为控制网格的二元箱样条曲面算法.二元三方向剖分是方向最少的三角剖分,建立在其上的二元三向四次箱样条在CAGD等领域有着广泛的应用.其规范的箱样条曲面计算仅适用于控制点的价数均为6的网格.从规范的算法出发,提出了一种任意价数控制网格的曲面计算算法,并对算法的连续性等进行了详细的分析.生成的曲面具有保凸性,且是分片C1连续的.该算法可进行3D离散点全局或局部插值,并可应用于3D曲面重构等领域.     

基于局部故障块三维mesh/torus网的容错路由

当系统包含很少的故障点时．mesh/torus网整个系统就有可能是不可靠的．该文采用扩展的局部可靠性信息来指导三维mesh／torus网的容错路由．扩展的局部可靠性信息在每个平面内部对无故障节点分类,所以系统中的故障块也是在不同的平面上构成的,而不是基于整个系统．很多基于整个系统不可靠的节点在二维的平面中都会变成可靠的节点．不管是在可靠的系统内,甚或不可靠的系统内,扩展的局部可靠性信息都能有效地指导容错路由．不同于以往的方法,作者的方法不会将任何无故障节点设置为无效节点．所有的故障块都是在平面内构成的,而不是基于整个系统;在一个平面内．任何包含在故障块里的无故障节点仍然可作为出发点或者目标点,这样将大大提高系统的计算能力和性能．模拟结果表明该文方法大大优于已有的方法．     

Perceptual Metrics for Static and Dynamic Triangle Meshes

Almost all mesh processing procedures cause some more or less visible changes in the appearance of objects represented by polygonal meshes. In many cases, such as mesh watermarking, simplification or lossy compression, the objective is to make the change in appearance negligible, or as small as possible, given some other constraints. Measuring the amount of distortion requires taking into account the final purpose of the data. In many applications, the final consumer of the data is a human observer, and therefore the perceptibility of the introduced appearance change by a human observer should be the criterion that is taken into account when designing and configuring the processing algorithms. In this review, we discuss the existing comparison metrics for static and dynamic (animated) triangle meshes. We describe the concepts used in perception‐oriented metrics used for 2D image comparison, and we show how these concepts are employed in existing 3D mesh metrics. We describe the character of subjective data used for evaluation of mesh metrics and provide comparison results identifying the advantages and drawbacks of each method. Finally, we also discuss employing the perception‐correlated metrics in perception‐oriented mesh processing algorithms.     

水下视觉环境感知方法与技术

有效感知水下环境是水下机器人自主运动与作业的关键。本文首先对水下视觉环境感知的共性问题进行分析,总结了视觉退化和折射畸变两大共性问题对水下视觉成像产生的影响。其次,围绕如何应对上述挑战,分别从水下视觉恢复方法、水下3维视觉感知以及水下视野增强方法3个方面对国内外主流的水下视觉环境感知方法的研究现状展开综述。最后,对水下视觉环境感知的未来发展趋势进行展望,重点包括集群化视觉感知、多模态感知信息融合、仿生视觉感知等热点研究方向。     

Analytical model for three-dimensional light-field displays based on voxel construction

Three-dimensional light-field displays (3D-LFDs) can provide viewers with glass-free 3D images. The display effect of reconstructed 3D images is closely related to the number of 3D object points that the 3D display system can construct, which can be regarded as the information quantity of the 3D-LFDs. However, the information quantity presented by a 3D-LFD is limited by fixed hardware parameters such as display panels and optical components. It is difficult to present an ideal 3D visual experience with the increase in display depth. In this paper, an analytical model based on voxel construction for 3D-LFDs is proposed, which can estimate the information quantity that a 3D-LFD can reproduce. The variation regularity of information quantity with display depth is analyzed and the influence of hardware parameters on display effect is discussed. With the proposed strategies, the display effect can be improved in a targeted manner without blurring and aliasing by adjusting the hardware parameters in display systems and matching the information quantity at different display depths.     

小型无人机三维导航控制研究

为提高小型无人机自主飞行的安全性能,更好地执行特定任务,在二维平面导航的基础上提出一种三维导航控制方法;给出三维导航控制器总体结构的设计,介绍了非定高下航程推算的原理,重点阐述了自主飞行中如何在平面导航基础上引入高度控制;利用Matlab/Simulink工具箱搭建仿真模型对三维导航控制律进行仿真验证;仿真结果表明,设计的控制方法切实可行,三维导航系统稳定性良好。     

基于LOD四叉树算法的中尺度云团三维流场可视化模拟分析

中尺度环流在复杂的天气环境下时常被大尺度环流掩盖,不能及时获取中尺度云团的时空密度,影响了中尺度云团三维流场可视化模拟效果,为了提升可视化模拟性能,提出基于四叉树算法（levels of detail,LOD)的中尺度云团三维流场可视化模拟分析方法。分析了中尺度云团三维相对流场,从中获取了中尺度云团三维流场运动规律,并基于二维直方图取得中尺度云团三维流场特征;将粒子源与四叉树结构相结合,构成四叉树粒子系统,把取得的特征映射到系统内,利用该系统中的粒子完成中尺度云团三维流场的渲染绘制,从而实现中尺度云团三维流场的可视化模拟。实验结果表明,绘制帧率对比测试、可视化模拟速率对比测试和可视化模拟效果对比测试结果清晰度较高,可视化程度较高,实用性强、可靠性高。     

面向网络应用的三维树木模型简化方法研究

在网络环境下进行三维树木模型的绘制与传输,不仅对模型逼真度有着较高要求,还更需保证网络交互的实时性。由于现有的基于几何或图像的三维模型简化方法无法满足网络应用对三维树木的模型细节和网络传输速度的要求,因此提出了一种面向网络应用的三维树木模型简化方法。该方法对树木枝干部分的骨架节点进行提取,并采用非均匀的骨架简化策略对树木模型的枝干部分进行简化;此外,还利用纹理树冠方法对树冠部分进行简化,通过采用凸包纹理模板贴图重构树冠,使得重构后得到的模型与原始模型具有很好的相似度。实验和应用结果表明,面向网络应用的三维树木模型简化方法在保证视觉质量的基础上,能进一步减少模型文件的存储容量,从而提高树木模型的绘制效率及其在网络中的传输速率。     

一种针对基于图像的3D重建网格的简化算法

文章提出了一种针对“基于图像的曲面3D重建网格”的简化算法,利用原曲面光照图像的等灰度值曲线来确定初始简化三角网格,然后通过若干次细分操作改善三角网格的形状,从而形成最终的简化网格。由于所有计算都在平面图像上进行,使得复杂的三维网格简化计算变成相对容易的平面网格简化计算,并同时具有保持原曲面的显示效果的优点。实验结果显示,该算法具有高效的计算速度和良好的显示效果保持特性,并可望应用到更广泛的高度场数据的简化方法中。     

基于Multigen Creator某飞行器视景仿真模型优化设计

根据飞行视景仿真和某飞行器模型的特点,利用Multigen Creator对导入的三维机械模型进行重新建模和优化。从如何修改模型数据库结构和减少模型复杂度和尺寸等方面入手,对飞行器的视景三维仿真模型的建立和优化方法进行了研究,解决了模型的逼真度和视景仿真的实时渲染速度之间的矛盾,最后对优化前后的模型通过在飞行视景仿真实验中的调用得到对比参数,表明了这种优化策略对提高复杂模型驱动速度、仿真效果和节省计算机资源开销有着很大必要性。     

飞行模拟训练分布交互视景仿真系统研究

创建了具有LOD(Levels of Detail)层次细节优化的三维地形模型、飞行器模型和环境物体模型,采用Vega软件的Symbology (仪表)模块、Creator建模中的DOF(Degrees Of Freedom)技术和Opengl程序设计技术,开发了精细的虚拟座舱仪表模型,并完成了基于飞行器视点和地面多视点的各视景仿真联邦成员的软件开发,构建了符合HLA标准的飞行模拟训练分布交互视景仿真系统,为飞行员和地面工作人员协同配合训练提供了先进的环境仿真实验平台.     

多体模型的三角形网格可控边折叠方法研究

多体模型在3DGIS中使用三角网表达,地质体之间因空间相邻关系存在公共面。目前网格简化方法主要针对单体模型,无法满足多体模型网格简化需要。提出了基于可控序列的边折叠条件分离相邻边界内外的公共面和非公共面部分,并使多体简化过程统一处理。实验分析表明该方法能够满足多体模型简化要求,并能处理地学中带有约束条件的顶点。     

Depth perception for moving images shown on a large LED display with an aperture grille

Abstract— A type of depth illusion created by the use of an aperture grille is reported. When viewing a moving target through multiple slits, a movement with depth is perceived, which was originally reported (see Ref. 11). The binocular delay is considered to cause a virtual disparity between both perspective images with apparent movement. By using an LED display with an aperture grille as a stereoscopic display, perceived distance caused by a binocular delay has been measured. The measured distance is compared with the perceived distance for stereoscopic still images shown on a stereoscopic LED panel. The comparison supported that the binocular delay is converted into binocular disparity. Furthermore, pair‐comparison tests were conducted to investigate depth impressions. It was found that use of an aperture grille improves depth impression for a movie that was taken with a laterally moving camera.     

基于局部高度与Mean Shift的三维模型信息隐藏算法

针对基于载体的秘密通信的需求,提出利用模型点Mean Shift聚类分析的三维模型载体信息隐藏算法。该算法将局部高度引入到模型点显著性衡量中,用以描述顶点的能量和结构特性,并用Mean Shift聚类分析法将各个顶点按照局部高度值分为能量特性不同的3类。以3类顶点为载体,采用隐藏信息与载体能量特性匹配的方式,通过修改3类顶点的结构特性指标,实现不同信息的嵌入。实验结果显示,该算法各项性能均衡,尤其具有较好的抗分析性和感知篡改性,且嵌入容量较大。     

A highly solid model boundary preserving method for large-scale parallel 3D Delaunay meshing on parallel computers

In this paper, we propose a novel parallel 3D Delaunay triangulation algorithm for large-scale simulations on parallel computers. Our method keeps the 3D boundary representation model information during the whole parallel 3D Delaunay triangulation process running on parallel computers so that the solid model information can be accessed dynamically and the meshing results can be very approaching to the model boundary with the increase of meshing scale. The model is coarsely meshed at first and distributed on CPUs with consistent partitioned shared interfaces and partitioned model boundary meshes across processors. The domain partition aims at minimizing the edge-cuts across different processors for minimum communication cost and distributing roughly equal number of mesh vertices for load balance. Then a parallel multi-scale surface mesh refinement phase is iteratively performed to meet the mesh density criteria followed by a parallel surface mesh optimization phase moving vertices to the model boundary so as to fit model geometry feature dynamically. A dynamic load balancing algorithm is performed to change the partition interfaces if necessary. A 3D local non-Delaunay mesh repair algorithm is finally done on the shared interfaces across processors and model boundaries. The experimental results demonstrate our method can achieve high parallel performance and perfect scalability, at the same time preserve model boundary feature and generate high quality 3D Delaunay mesh as well.