三角网模型叠加法在土方计算中的应用探讨

介绍了依托AutoCAD平台计算不规则设计面土方量的方法,并提出通过对开挖前后2次观测数据分别建模并相互叠加来找出填挖线的技巧.     

建TIN的几种算法比较

TIN是由三角形构成的一种有限元网格,它主要用来表示地形或地物表面。本文从几种不同建TIN的算法（三角网生长算法、凸壳算法、前沿边推进算法和贪心算法）来比较和分析各算法的优缺点。     

The stochastic walk algorithms for point location in pseudo-triangulations

A pseudo-triangulation is a planar subdivision into polygons with three convex vertices, useful for ray shooting, visibility problems and kinetic collision detection. As pseudo-triangulations are quite young, there is a lack of specialized algorithms for them. In this paper, we address the question of location in pseudo-triangulations. We propose two location algorithms based on the so-called stochastic walk and present their experimental results. The class of walk location algorithms is very popular for triangulations, namely in engineering applications, due to simplicity and low memory requirements, in spite of their non-optimality. As far as we know, no walk algorithm specialized on pseudo-triangulations has been developed before.     

基于Delaunay三角剖分的多目标进化算法解集分布度评价指标

系统分析目前多目标进化算法(MOEAs)分布度评价指标的特点和不足,提出一种基于Delaunay三角剖分的分布度评价指标。该指标将基于邻域和基于距离的评价思想相结合,利用Delaunay三角网最近邻与邻接性的特点实现自主邻域划分。采用空间映射的方法,有效减少MOEAs解集非支配关系对种群分布度评价的影响。测试结果表明该指标能准确反映MOEAs解集的分布性。     

起爆延期等时线的生成及其应用研究

提出了延时爆破工程中起爆延期等时线的概念,阐述了等时线的生成及其计算机辅助制图原理,并以典型工程方案为例,对等时线在爆破工程中的应用效果进行了检验。结果表明,等时线分析技术在预测爆破、方案优化设计?判断爆破瞬间自由面生成形态与爆破体抛掷主导方向以及爆破效果等方面,具有便捷直观?可靠有效等优点。     

基于目标检测的SAR图像变化检测方法

SAR图像变化检测有着广阔的应用前景,但目前的方法普遍以精确的配准为前提,使其适用范围受到限制。针对人造目标在SAR图像上的特点,提出了一种基于目标检测的SAR图像变化检测方法。通过图像中的人造目标之间相对位置关系的相似程度确定图像的变化情况,以此来降低对图像配准精度的要求。实验表明该方法在很宽的配准精度范围内都可获得较满意的结果。     

基于Delaunay三角形网格的彩色视频帧内编码方法

利用DT(Delaunay Triangulation)网格研究了彩色视频亮度和色度分量之间的相关性,提出了一种基于DT网格的彩色视频帧内编码方案．该方案仅对亮度分量Y进行DT描述,利用亮度分量Y的部分网格节点经过相似变换生成色度分量Cb或Cr的DT网格,从而节约了编码时间．实验结果表明,与对3个分量分别进行DT描述及编码的方法相比,节约了约30％的编码时间,并保持了好的解码图像,仍然比H. 263帧内编码和MPEG-4的静态纹理编码方法提供的主观质量好．     

Efficient CAD-based triangulation of unordered 3D data

Abstract. The paper proposes a new method for efficient triangulation of large, unordered sets of 3D points using a CAD model comprising NURBS entities. It is primarily aimed at engineering applications involving analysis and visualisation of measured data, such as inspection, where a model of the object in question is available. Registration of the data to the model is the necessary first step, enabling the triangulation to be efficiently performed in 2D, on the projections of the measured points onto the model entities. The derived connectivity is then applied to the original 3D data. Improvement of the generated 3D mesh is often necessary, involving mesh smoothing, constraint-based elimination of redundant triangles and merging of mesh patches. Examples involving random measurements on aerospace and automotive free-form components are presented. Received: 30 August 1999 / Accepted: 10 January 2000     

Bundle adjustment of multi-position measurements using the Mahalanobis distance

Precision three-dimensional metrology frequently involves the measurement of common points by several three-dimensional measurement systems. These can be laser tracking interferometers, electronic theodolites, etc. A new analysis technique has been developed that fully takes into account the uncertainty ellipsoid for each measurement point. This technique solves for the positions and orientations of the measurement systems while determining the optimal fit to each physical point. No a priori knowledge of the location and orientation of the measurement systems is required. An initial estimate for the location and orientation of the measurement systems is derived from the measurement data by assuming equal uncertainties for each data point. Then a merit function is minimized to determine the optimized location and orientation of the measurement systems and the weighted mean for the position estimates of the physical points. This merit function is based on the Mahalanobis distance from multivariate statistics and takes into account the particular shape and orientation of the three-dimensional uncertainty ellipsoid of each data point from each measurement system. This technique can utilize data from differing types of three-dimensional measurement systems including distance only and angle only measurements, evaluate the “strength” of a measurement configuration and accommodate missing data points from some of the measurement systems.     

Piecewise linear mapping functions for image registration

A new approach to determination of mapping functions for registration of digital images is presented. Given the coordinates of corresponding control points in two images of the same scene, first the images are divided into triangular regions by triangulating the control points. Then a linear mapping function is obtained by registering each pair of corresponding triangular regions in the images. The overall mapping function is then obtained by piecing together the linear mapping functions.