【作者】 方贵盛；

【导师】 孔繁胜； 何利力；

【作者基本信息】 浙江大学 ， 计算机科学与技术， 2007， 博士

【摘要】 概念设计是产品开发的早期阶段，具有信息不完全和不精确等特点。而当前的CAD系统需要输入精确的尺寸和位置信息，造型过程较为繁琐、耗时，无法胜任概念设计阶段的工作。在概念设计阶段，设计师们往往先采用纸笔草绘来快速表达产品的形状构思，只有当产品信息完全确定以后，才开始借助计算机进行辅助设计以及后续的分析加工仿真等。这就造成纸笔草绘与计算机辅助设计两者之间的脱节，更为重要的是设计与造型往往是分开进行的，甚至是由不同的人来完成的，这样信息在表达传递过程中容易丢失。计算机辅助草绘技术由于结合了计算机与纸笔草绘的众多优点，能够帮助设计师在产品的概念设计阶段利用计算机来快速记录头脑中产生的瞬时灵感。近年来一直是许多专家学者争相研究的热点课题之一。不过现有的计算机辅助草绘设计系统存在用户适应性差、草图识别精度不高等缺点，使其应用受到一定的限制。本文主要面向工程概念草图识别与草绘建模的需要，针对现有计算机辅助草绘设计系统存在的一些问题，从二维草图识别与规整、基于手势的草图编辑、基于意图捕捉的三维草绘建模技术等三个方面着手解决计算机辅助草绘设计一些关键技术的实现难点，并提出了一套行之有效的算法，然后与现有的算法进行了分析比较。所研究的主要内容和取得的创新性研究成果主要包括以下几个方面：1．将用户草绘笔划识别分解为笔划预处理、特征点的检测、笔划分段、图元识别、图元重构、图元规整、端点校正等几个步骤分层进行处理，并开发出相应的实现算法，从而可以将用户随意绘制的草绘笔划转化为规整的几何图形，以正确理解用户的概念表达意图，并解决了整体草图识别所带来的算法复杂度过高，识别出错难以修改等缺点。2．面向工程概念草图编辑的需要，设计出一套简单高效的带草图编辑参数的笔式手势集。然后在分析现有手势识别方法的基础上，开发出一个可训练的手势识别器，尝试采用多种机器学习方法对笔式手势进行识别，以解决现有手势识别算法识别精度不高和用户适应性不强等缺点。深入研究和实现了笔式用户界面环境下针对草图修改的多种基于手势的编辑算法，如对象选择、复制、移动、旋转等，解决了现有CAD系统图形编辑过程繁琐、费时等缺点。3．提出了一种基于草绘笔划的概念模型创建方法，模仿传统的纸笔草绘交互设计方式，利用意图捕捉机制揣测用户的设计意图，将基于Parasolid创建Sweep特征的核心算法应用到产品概念设计过程中，并通过引入特征切削及添加操作自动判别机制由简单的产品模型构造出复杂模型，最后给出了一些关键算法的实现过程。相对于现有的草绘建模方法，该方法具有建模过程简单，建模效率高，建模范围广等优点，能够允许用户直接在概念模型表面上草绘截面笔划和轨迹笔划构造概念模型。尝试实现了两种基于手势的模型编辑操作。4．采用面向对象的设计方法，结合本文所提出的算法，开发实现了面向二维工程草图设计与编辑的草绘设计系统Sketch2D和面向产品概念模型快速表达的草绘建模系统Sketch3D。它们是本文相关草绘设计思想和方法的应用和验证。针对二维草绘设计系统Sketch2D，本文给出了其基本体系结构和基本数据模型，实现了在线识别技术与手势编辑方法，允许用户通过简单的笔式草绘技术勾画概念草图，并进行快速编辑，避免繁琐的菜单操作等，然后与现有的CAD系统及原有的计算机辅助草绘系统进行了综合比较，体现出系统的优越之处。针对三维草绘建模系统Sketch3D，同样给出了其基本体系结构及其主要功能，并和目前流行的三维CAD系统及现有的一些三维草绘设计系统进行了比较，总结出其主要优缺点。更多还原

【Abstract】 Conceptual design is the initial stages of product development which is characterized by inadequate and vague design information. However, current CAD systems need to input precise dimensional and geometric constraints information in the process of product modeling. At the same time, the use of WIMP-based user interface makes the process of modeling very cumbersome, tedious and time-consuming. These reasons make current CAD systems mainly be suited for the detailed design and not the conceptual design. In the conceptual design stage, designers usually use pencil and paper to rapidly record their creative ideas. Only when the configuration of the product is determined fully, the digital model will be constructed by using the computer aided design technologies. Because the design and the modeling process are separate, some important information will be lost during information conveyance. Combining the flexibility and ease of use of paper and pencil with the processing power of the computer, Computer Aided Sketching Design (CASD) technology specially suits for conceptual design and can help designer write down design ideas rapidly. For many years it has been one of key issues which many specialists and scholars research. The present situation of CASD is introduced firstly. And then some key technologies of CASD, that is pen-based user interface design, sketch recognition and beautification, gesture-based sketch editing, 3D sketching modeling, are analyzed. The main research contents and achievements are articulated as follows:(1) Some basic theories and algorithms on sketching design and sketch recognition have been researched, such as sketch preprocessing, feature points detection, strokes fragment, primitives recognition, shape reconstruction, and primitives beautification, etc. The aim is integrating users’ sketching styles and the abilities of recognizing sketch with the technologies of CAD in order to develop new intelligent CAD systems.(2) The gesture is an important interactive way to realize a certain operation for sketch editing. In order to realize online conceptual sketch editing, some kinds of gestures have been designed and defined, such as delete gestures, move gestures, copy gestures, rotate gestures, etc. These gestures have been recognized by using a trainablegesture recognizer. In order to improve the recognition efficiency and the user adaptation of gestures, several recognition algorithms have been used. Finally, A series of algorithms for sketch editing based on pen gestures are presented.(3) A simple, rapid, efficient approach to construct 3D conceptual solid models on sketch-based user interface is presented. It emulates the traditional sketching design approach with paper and pencil metaphor to sketch strokes on the calligraphic interface, and then applies the feature-based modeling method to construct different sweep feature-based primitives according to the shape and location relationship of feature strokes. In order to construct complex solid models, the feature joining and cutting mechanism based on intention capturing is introduced. Additionally, a gesture-based model editing method is presented briefly. We illustrate the implementation of the algorithm and experiments show that our algorithm is efficient and well suited for real time on-line 3D conceptual model creation.(4) The Sketch2D system, a sketching design system for engineering sketch design and editing, and the Sketch3D system, a sketch-based modeling system for conceptual expression of products, have been developed by using the object-oriented design method and the technologies of current CAD. Some basic frame structures and functions of the systems have been presented. Some experimental examples have been provided to verify the efficiency of the recognition and modeling algorithms. Finally, some capabilities of the SketchXD system (the abbreviation of the Sketch2D system and the Sketch3D system) have been compared with the current CAD systems such as AUTOCAD, Pro/Engineer, etc., and some classical sketching design systems such as SILK, SKETCH, etc.更多还原