工程设计中多图联动建模技术的研究与应用

工程设计中多图联动建模技术提供用户友好的工程设计空间,建立了工程原理图和多个工程布置图之间的信息关联。采用3D数据存储——2D图形可视转换技术,得到图形变换矩阵。把设备的各个视图的图块预存入图形库中,绘图时,设置相应的绘图图层,只要在布置图的一个视图中插入设备图,系统会在其他视图中自动插入相应的投影图形,并且当修改或者删除一个视图中的图形时,其他视图对应的图形也会自动完成相应的操作,实现了多个工程视图的联动。     

关联图形参数化原理与方法研究

该文对基于关联图形的几何建模参数化原理与方法做了较为系统的研究。文中介绍了关联图形及其相关概念,并在此基础上给出了关联图形的表达、基于关系模型的关联图形的组织、关联图形的联动以及关联图形循环约束问题的解决等基本原理与方法。     

三维实体重建时投影图数据的预处理

介绍三维实体重建过程中投影图数据的处理算法，绘制同一图层的图形时，视图分割算法添加平行于两坐标轴的辅助直线，移动辅助线使其将三视图分割开来；对基于同一坐标系的投影三视图数据，推出从设备坐标系到各视图坐标系的转换公式并为其设计了转换算法，该算法求出三视图坐标系共有的原点，再根据视图分割的结果将每一图形元素转换到新的坐标系统中；隐含点的求取算法先判断同一视图中图元间的位置关系，再求出它们之间的公共点，这些点将用于线框搜索过程中，以上算法处理的投影图点线数据分别存入点线链表中。     

从正交三视图重建复杂组合体

针对具有复杂遮挡关系的组合体三视图轮廓搜索不完备的问题,提出基于动态子视图划分的投影轮廓搜索算法.在应用传统角度判别法找出三视图中所有基环后,以基环为线索动态地划分单向子视图并搜索惯性环,对已找到的环进行二元组匹配,依据二元匹配组动态地划分双向子视图并搜索惯性环;从已找到的所有环中搜索基本形体的投影轮廓,通过拉伸或旋转构建基本形体,对基本形体应用正则布尔运算形成三维形体.实验结果表明,该算法可以完备地搜索出构成复杂组合体的基本形体投影轮廓,包括被遮挡的部分,保证了三维重建的正确性.     

基于约束的参数化设计与建库工具研究

本文提出了基于约束参数化设计与建库工具的研究思想及实现方法，较为详细地讨论了图形的几何约束信息、结构约束信息，并且研究了图形结构约束与尺寸约束的自动识别、驱动求解等关键技术，采用了双向十辽链表存储尺寸链稀疏矩阵并解决了其双向遍布问题，实现了复杂图形的安全参数化尺寸驱动以及多视图的联动、并对约束检测及约束个性提出了合理有效方法。该方法为产品修改、仿型设计用变量化动态仿真设计提供的有效手段，特别是为系     

基于约束的参数化设计与建库工具研究

本文提出了基于约束的参数化设计与建库工具的研究思想及实现方法，较为详细地讨论了图形的几何约束信息、结构约束信息，并且研究了图形结构约束与尺寸约束的自动识别、驱动求解等关键技术，采用了双向十字链表存储尺寸链稀疏矩阵并解决了其双向遍历问题，实现了复杂图形的完全参数化尺寸驱动以及多视图的联动，并对约束检测及约束修改提出了合理有效的方法。该方法为产品修改、仿型设计和变量化动态仿真设计提供了有效手段，特别是为系列化产品设计提供了一理想的参数化建库工具。     

尺寸关联约束的识别及求解方法的研究

针对尺寸之间的关联约束，本文首先分析了尺寸链约束的特点，提出了基于尺寸链的尺寸环模型．通过对尺寸和被约束图形对象的识别与理解，研究了尺寸链、尺寸环建立和尺寸环中的尺寸到被约束元素之间的约束关系的映射算法，实现了尺寸关联约束的识别和求解．     

一种基于AKAZE算法的多视图几何三维重建方法

针对增量式运动恢复结构算法在多视图几何三维重建算法中运行效率低的问题,提出了一种基于AKAZE算法的多视图几何三维重建方法。首先对利用摄像机获得的目标图像使用AKAZE算法检测特征并匹配,并使用随机抽取一致性算法和三视图约束剔除弱匹配图像。然后根据匹配图间的相对位姿参数,通过最小二乘法解算全局旋转参数,并利用三视图约束关系求解全局位移参数。最后进行一次光束法平差优化。实验结果表明,该算法在改善重建效果的基础上提高了处理效率,能够满足快速处理的需求。     

对三视图的DXF图形数据进行特征识别与立体重构

本文介绍了一种对在ＡｕｔｏＣＡＤ环境下绘制的三视图的ＤＸＦ图形数据进行特征识别和立体重构的原理与方法；通过对三视图的ＤＸＦ图形数据的分析，利用三视图的尺寸标注信息，可以将ＤＸＦ文件提供的三视图进行自动分离，按特征建模的要求对各视图的实体进行特征识别和特征分类；采用特征文件作为媒介，利用ＣＳＧ模型，可以将识别的特征在ＡｕｔｏＣＡＤ环境下重构出来；本文的方法不仅能识别ＡｕｔｏＣＡＤ系统设计的零件，产生     

基于关联约束的单元建模技术研究

以图形元素和关联算子为基础定义结构单元，并赋以特定工程含义，使之成为包含结构信息和图形信息的基本设计单位；定义了主矢的概念来描述单元的总体特征，归纳了三种类型的关联约束，建立了单元化结构模型，实现了产品的结构变动设计。     

Viewpoints: principles, problems and a practical approach to requirements engineering

The paper includes a survey and discussion of viewpoint‐oriented approaches to requirements engineering and a presentation of new work in this area which has been designed with practical application in mind. We describe the benefits of viewpoint‐oriented requirements engineering and describe the strengths and weaknesses of a number of viewpoint‐oriented methods. We discuss the practical problems of introducing viewpoint‐oriented requirements engineering into industrial software engineering practice and why these have prevented the widespread use of existing approaches. We then introduce a new model of viewpoints called Preview. Preview viewpoints are flexible, generic entities which can be used in different ways and in different application domains. We describe the novel characteristics of the Preview viewpoints model and the associated processes of requirements discovery, analysis and negotiation. Finally, we discuss how well this approach addresses some outstanding problems in requirements engineering (RE) and the practical industrial problems of introducing new requirements engineering methods.     

一种基于问题框架的视点表示模型

在多视点需求工程中，视点表示模型与视点需求信息的获取、描述密切相关，影响着后阶段视点一致性的检查和集成。鉴于需求工程领域的发展，该文提出了一种基于问题框架的视点表示模型，展示了该模型的特点及应用。实践表明，该模型具有实用性和可操作性。     

体数据可视化的线绘制视频

提出一种线绘制视频的可视化方法．一方面，基于体数据和视点的重要性度量使视频能从更有效的视点来观察体数据，并且每帧图像都能对数据场的内容有很高的反映强度；与此同时，视点连续高效地变化，也有利于用户形成关于数据场内容的完整印象．与先进的基于线绘制的交互可视化方法相比，新方法的成像速度和可视化反映强度更高，能以更少的可视化图像达到对数据场内容更全面的认识．     

一种基于行为的多视点需求描述方法

传统多视点方法存在着诸多不足之处。本文在此基础上提出了一种基于行为的多视点需求描述方法（BVORA）,从行为的角度对需求进行了描述,提出了以场景对视点进行划分的方法,给出了视点的定义以及视点表达,定义了视点间的关系。     

基于视平面上特征计算的视点选择

提出一种能高效观察三维模型的视点选择方法.该方法基于视平面定义一种曲率特征,以度量模型的三维几何特征在视平面上的分布和体现状况,并由此计算与视点相关的一种熵值;然后对各个视点相关的这种熵值进行比较,可得到熵值最大的视点.实验结果表明,采用该方法找到的视点能观察到模型尽可能多的显著特征,与人眼的观察习惯比较接近.与已有方法相比,文中方法计算简单、不需要语义计算、有较高的工作效率.     

Camera movement for chasing a subject with unknown behavior based on real-time viewpoint goodness evaluation

We propose a method that automatically generates a smooth chase camera movement to follow a subject, a user-controlled character or a character with unknown behaviors, in a 3D environment freely in real time. We consider three objectives in generating the smooth-camera movement: to avoid collisions with obstacles, to avoid subject occlusions, and to choose a good viewpoint for looking at the subject. We evaluate the goodness of viewpoints by using a viewpoint entropy map and choose the best viewpoint as the goal position of the camera in real time. Afterwards, we move the camera toward the goal position by following the shortest path, found by the A* algorithm, on a roadmap graph. The resulting camera movement has a high degree of freedom and fulfills the three objectives above. Our method is effective for third-person-view 3D applications in tracking the real-time movement of user-controlled characters in exploring a 3D environment.     

ClipFlip : Multi‐view Clipart Design

We present an assistive system for clipart design by providing visual scaffolds from the unseen viewpoints. Inspired by the artists' creation process, our system constructs the visual scaffold by first synthesizing the reference 3D shape of the input clipart and rendering it from the desired viewpoint. The critical challenge of constructing this visual scaffold is to generate a reference 3D shape that matches the user's expectations in terms of object sizing and positioning while preserving the geometric style of the input clipart. To address this challenge, we propose a user‐assisted curve extrusion method to obtain the reference 3D shape. We render the synthesized reference 3D shape with a consistent style into the visual scaffold. By following the generated visual scaffold, the users can efficiently design clipart with their desired viewpoints. The user study conducted by an intuitive user interface and our generated visual scaffold suggests that our system is especially useful for estimating the ratio and scale between object parts and can save on average 57% of drawing time.     

A comparative study of the robustness of two pose estimation techniques

The paper presents an analysis of the stability of pose estimation. Stability is defined as sensitivity of the pose parameters towards noise in image features used for estimating pose. The specific emphasis of the analysis is on determining {how the stability varies with viewpoint} relative to an object and to understand the relationships between object geometry, viewpoint, and pose stability. Two pose estimation techniques are investigated. One uses a numerical scheme for finding pose parameters; the other is based on closed form solutions. Both are “pose from trihedral vertices” techniques, which provide the rotation part of object pose based on orientations of three edge segments. The analysis is based on generalized sensitivity analysis propagating the uncertainty in edge segment orientations to the resulting effect on the pose parameters. It is shown that there is a precomputable, generic relationship between viewpoint and pose stability, and that there is a drastic difference in stability over the range of viewpoints. This viewpoint variation is shared by the two investigated techniques. Additionally, the paper offers an explicit way to determine the most robust viewpoints directly for any given vertex model. Experiments on real images show that the results of the work can be used to compute the variance in pose parameters for any given pose. For the predicted {instable} viewpoints the variance in pose parameters is on the order of 20 (degrees squared), whereas the variance for robust viewpoints is on the order of 0.05 (degrees squared), i.e., two orders of magnitude difference.