三维井眼轨迹仿真研究

在曲线插值算法和图形透视原理研究的基础上,将离散的井眼轨迹数据通过插值算法平滑化,并通过三维透视投影原理实现其三维仿真.在理论研究的基础上,利用Visual Basic开发了三维井眼轨迹仿真系统,该系统能进行三维井眼轨迹放大、缩小、旋转等操作,可从多方位和角度观察仿真结果.     

《关于透视变换的研究》一文商榷

1　引　　言在《关于透视变换的研究》(以下简称为文献[1 ])一文中提出 :“二点透视是经旋转平移方法得到的”,这种提法不符合二点透视投影等基本概念 ,但文中论证较难令人信服 .问题的关键在于对一些基本概念应该如何理解 .以下将说明对于一些概念我们与文献 [1 ]的不同理解 ,与作者及同行商榷 .2　透视投影和透视变换文献 [1 ]中的第 1句就提到 :“计算机图形学中的透视变换……”,严格地说 ,“透视投影”和“透视变换”不相同 .计算机图形学中关心的是透视投影 ,因为它要解决在二维表面上绘制三维形体的问题 .透视投影是已知投影中心和投…     

旋转体的图案绘制和消隐技术

本文通过数据输入形式、旋转体的表示方法、图案绘制原理、坐标变换、投影方法、隐线处理等六方面的研究,开发了旋转体的三维表示及图案绘制方法,并研究成功消除隐线的新方法。     

基于旋转螺旋屏的三维立体成像系统研究

针对前两代体三维(V3D)成像系统存在图像轮廓不够清晰问题,提出并实现了一种基于空间光调制器和双螺旋投影面的被动式旋转体扫描三维(RSV3D)成像系统。分析了系统的组成和工作原理,并详细讨论了组成系统的三大功能模块:成像空间、体素激活装置和V3D引擎的硬件与软件设计思想,并提出了多螺旋切片图形的重构算法和优化处理措施相结合的方案,以降低三维图像海量数据的传输和存储难题。实验结果显示:该系统可以产生高清晰度的空间三维图像,验证了该系统研制方案的可行性。     

PTZ摄像机视频与三维模型的配准技术研究

针对基于投影纹理映射的虚实融合系统,提出了一种PTZ摄像机视频与三维模型实时配准的技术.选取PTZ摄像机若干特定姿态的子图像组成一张全景图像,进行最优匹配图像的搜索,用SURF图像配准的方法对实时视频图像进行透视变换,利用最优匹配图像的三维投影信息将实时视频图像精确投影到三维模型中.实验结果表明,该算法具有较高的准确性,适用于虚实融合系统中PTZ摄像机视频的三维配准.     

从一幅透视图象重建三维对称形体

本文提出 一种利用一幅透视图象重建对称形体的算法，通过对透视图中灭点位置分布规律的解析求出透视投影时视点的位置以及物体的对称平面后，即可唯一地确定物体上任意一对对称点的三维坐标。     

基于视点相关透视纹理的矢量数据在三维地形上的叠加绘制

为了精确、高效地将传统二维矢量数据叠加到三维多分辨率地形上,提出一种基于视点相关透视纹理的叠加绘制算法.首先通过场景视点得到能充分逼近当前地形可视范围的透视投影,然后用该透视投影实时地将二维矢量数据绘制在与地形绑定的纹理上,同时在GPU中并行计算出纹理坐标.与传统的基于纹理的绘制方法相比,视点相关的透视投影能够提高纹理的像素利用率,从而减轻传统方法所产生的走样问题,提高矢量数据的绘制质量;且该算法不受地形几何数据的约束,能够与目前大多数多分辨率地形模型以及影像金字塔很好地结合在一起使用.     

三维空管自动化系统投影技术研究

新一代空中交通管理系统的核心任务是对飞行器的四维航迹进行管理,而实现四维航迹有效显示的重要途径之一为三维透视投影技术。针对空管自动化系统的实际需求,求得三维空间透视投影的旋转矩阵及投影矩阵,给出一种新的投影算法,并结合三维地图软件对实际飞行器的标牌显示进行实验。实验结果表明所提出的方法可以实现三维空间到二维投影面的变换,是一种有效且可行的三维空间透视投影算法。     

三维场景中高分辨率输出技术的研究

论文围绕三维景观系统中的高分辨率输出技术进行了分析与探讨,针对传统输出方法因受帧缓冲大小的限制所存在的不足之处,提出了一种新的行之有效的高分辨率输出方法。其主要思想是对整个三维场景采用“分而绘之”的方法,通过动态调整透视投影参数来达到不同区域场景的高分辨率独立绘制,并最终获得满足要求且无缝拼接的三维渲染效果图。     

正多边形剖分球面投影及其应用

提出了利用正多面体顶点分布来剖分球面,得到球面上物体的投影点,利用这些投影点得到物体的二维投影。这种二维投影的获取方式具有投影点分布均匀的特点,并且根据三维物体的特点对特定区域的投影点进行加密,以获取更多的二维投影信息。该方法已经应用到三维模型及三维动作的识别中,取得了良好的效果。     

Free vibration analysis of complete paraboloidal shells of revolution with variable thickness and solid paraboloids from a three-dimensional theory

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid paraboloids and complete (that is, without a top opening) paraboloidal shells of revolution with variable wall thickness. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. The ends of the shell may be free or may be subjected to any degree of constraint. Displacement components u_r, u_θ and u_z in the radial, circumferential, and axial directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the paraboloidal shells of revolution are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the complete, shallow and deep paraboloidal shells of revolution with variable thickness. Numerical results are presented for a variety of paraboloidal shells having uniform or variable thickness, and being either shallow or deep. Frequencies for five solid paraboloids of different depth are also given. Comparisons are made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.     

电容层析成像系统三维图像重建的研究

探讨了电容层析成像(ECT)系统中利用二维断层图像进行三维表面重建并由三维图像求取两相流中离散相体积和观察其空间位置的方法。首先对二维断层图像序列进行轮廓抽取和细线化，然后进行轮廓匹配和轮廓插值并进行表面重建。初步的仿真结果表明，使用的三维重建算法简单、重建精度高、成像速率快。     

Display techniques and boundary evaluation of a Sweep-CSG modeller

Among the various techniques for displaying solid objects, ray tracing is the most popular method for sweep-generated objects, owing to its simplicity and effectiveness. The main problem in ray tracing is to find the point of intersection between the ray and the object. By taking consideration of the special features of a surface generated by sweep, the ray/object intersection problem can be reduced to 2-D planar problem. This paper presents a raycasting technique for displaying Sweep-CSG-represented solids. This technique works directly on the Sweep-CSG representation and does not require explicit boundary information. Boundary information is, however essential for line-drawing outputs. In this paper, boundary-evaluation techniques for obtaining edges of a Sweep-CSG solid are described. Special techniques for evaluating the boundaries of a solid generated by sweeping another solid are also discussed.     

刀具CAD中的三维立体造型技术

本文介绍了刀具ＣＡＤ图形处理中的三维立体造型技术。采用几何体素构造法和变差几何法参数化实体造型技术来生成加工中心刀具的绘图模型，并给出了按拓扑关系自动查询图形数据库的方法。     

On the Characterization of Absentee-Voxels in a Spherical Surface and Volume of Revolution in $${\mathbb Z}^3$$

We show that the construction of a digital sphere by circularly sweeping a digital semi-circle (generatrix) around its diameter results in the appearance of some holes (absentee-voxels) in its spherical surface of revolution. This incompleteness calls for a proper characterization of the absentee-voxels whose restoration in the surface of revolution can ensure the required completeness. In this paper, we present a characterization of the absentee-voxels using certain techniques of digital geometry and show that their count varies quadratically with the radius of the semi-circular generatrix. Next, we design an algorithm to fill up the absentee-voxels so as to generate a spherical surface of revolution, which is complete and realistic from the viewpoint of visual perception. We also show how the proposed technique for absentee-filling can be used to generate a variety of digital surfaces of revolution by choosing an arbitrary curve as the generatrix. We further show that covering a solid sphere by a set of complete spheres also results to an asymptotically larger count of absentees, which is cubic in the radius of the sphere. A complete characterization of the absentee-voxels that aids the subsequent generation of a solid digital sphere is also presented. Test results have been furnished to substantiate our theoretical findings.     

Applications of 3-D finite element procedures to static and dynamic problems in micropolar elasticity

Based on micropolar elasticity theory, 3-D finite element formulations are developed for bodies of revolution as well as those of arbitrary shape. In contrast to the general 3-D formulation which uses completely approximate shape functions, the axisymmetric development which can handle asymmetric problem is based on a quasi-analytical procedure. Both the general and body of revolution developments have the capacity to handle static as well as dynamic problems involving structures composed of possibly fully anisotropic materials. To reveal the accuracy of the formulations as well as the potential importance of micropolar effects, several numerical experiments are included in this paper.     

A linear signal decomposition approach to affine invariant contour identification

Means for the identification of objects from contours despite affine transform induced distortions using a linear signal space decomposition are described. This technique also yields robust estimates of the 3-D rotations of a near planar object. The ability to determine object identity and orientation from a single model representation without iteration or combinatorial search proceeds from the use of affine invariant differential measures derived via Lie group theory. The technique is extremely robust owing to the error rejection properties of signal space projections. Results illustrating the resilience of the solutions in the presence of severe non-affine distortion and pixelization are given.     

Validation of X-ray lithography and development simulation system for moving mask deep X-ray lithography

This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M/sup 2/DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M/sup 2/DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M/sup 2/DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA.     

ECT系统中三维图象重建的研究

论文讨论了在ECT系统中利用二维断层图象进行三维表面重建的方法。首先对二维断层图象序列进行抽取轮廓、细线化、轮廓线追踪处理;然后对两相邻断层图象进行轮廓匹配;在两层已知(重建)图象轮廓中间插入若干个插值图象时采用同经度方向位置校准轮廓加权平均方法获得插值轮廓;最后在相邻的已知轮廓或插值轮廓采用最短对角线法进行三角片表面重建。仿真结果表明,利用上述方法可以较好地重建物体的三维表面。     

Integration of topology and shape optimization for design of structural components

This paper presents an integrated approach that supports the topology optimization and CAD-based shape optimization. The main contribution of the paper is using the geometric reconstruction technique that is mathematically sound and error bounded for creating solid models of the topologically optimized structures with smooth geometric boundary. This geometric reconstruction method extends the integration to 3-D applications. In addition, commercial Computer-Aided Design (CAD), finite element analysis (FEA), optimization, and application software tools are incorporated to support the integrated optimization process. The integration is carried out by first converting the geometry of the topologically optimized structure into smooth and parametric B-spline curves and surfaces. The B-spline curves and surfaces are then imported into a parametric CAD environment to build solid models of the structure. The control point movements of the B-spline curves or surfaces are defined as design variables for shape optimization, in which CAD-based design velocity field computations, design sensitivity analysis (DSA), and nonlinear programming are performed. Both 2-D plane stress and 3-D solid examples are presented to demonstrate the proposed approach. Received January 27, 2000 Communicated by J. Sobieski