【作者】 武丹；

【导师】 王琰；

【作者基本信息】 沈阳理工大学 ， 计算机软件与理论， 2008， 硕士

【摘要】 基于工程图的三维形体重建技术是根据形体在二维投影视图中的几何信息和拓扑信息生成相应的三维形体,这是一个从低维到高维的构造过程,目前已成为CAD与CAM中的重要研究课题。其中工程图投影信息获取与处理作为三维重建工作的第一步,对重建工作起着重要作用。本文以辽宁省科技攻关项目为背景对基于特征识别的重建方法中工程图投影信息获取与处理技术做了较深入的研究,取得了一定的研究成果。主要内容包括:1.详细研究和分析了DXF文件的格式和存储结构,设计并编写了各图元的数据结构以及获取各实体图元信息的接口程序,分析了尺寸标注约束语义,总结出尺寸标注提取的规则的算法。2.在工程图视图分离方面,提出一种最小外接矩形的多视图分离方法,实现了对于各类非标准三视图的视图分离,包括一视图、二视图等,同时结合工程语义确定出视图的关系,实现从绘图坐标系到空间坐标系的转换。3.着重讨论了半剖视图的识别与处理方法,针对DXF文件格式,获取半剖区域信息,对由半剖视图所打断的形体轮廓线进行了恢复,并给出了具体的算法,降低了后续三维重建的难度。综上所述,本文从工程应用角度出发,提出了一整套工程图三维重建预处理方案。和传统方法相比,在预处理过程中加入了对语义信息和剖视信息的提取识别,能够更加准确、完整地获取和处理工程图中各类数据信息,将处理对象的范围从标准三视图拓展到实际工程图,以DXF工程图文件为数据源,从根本上拓宽了三维重建的适用范围。本文所给算法已在实际的三维重建系统中得到了实现,结果表明可以满足后续重建工作的需要。更多还原

【Abstract】 3D reconstruction technology based on engineering drawings is to construct 3D objects by use of geometric and topological information of 2D orthographic projection views. The process of construction is from lower dimension to high dimension, which has become an important research subject in CAD/CAM.As the first step of reconstruction, information extraction and processing plays an important role in 3D reconstruction. The thesis made deeply research to the technology of information extraction and processing in engineering drawings based 3D reconstruction method of characteristic recognition under the background of technological tacking key problem for Liaoning province, which obtains some production. The main contributions are summarized as follows:First, the format of DXF files and storing structure is researched and analyzed detailedly. Interface program to reading primitive date from DXF under CAD system is also designed and programmed. Analying the dimension mark restriction semantics and summarizing the algorithm of extracting dimension mark.Second, on views separation , it presents an multi-views separation method of the least circum-rectangle. It reduces times of travelling meta by setting a sign-bit in programming and implements separation of various nonstandard three views including one view, two views etc..Combining engineering semantics, it confirms the views relation and implements coordinate conversion from drawing reference frame to space reference frame.Third, the thesis emphatically discusses the method of recognition and processing to the half-cutaway views. According to the format of DXF files, the thesis presents and implements the algorithm that extracts the information of half-cutaway views. The algorithm recovers the figure which is cutted by half-cutaway views , which debases the difficulties for 3D reconstruction.To make a summary , the scheme of engineering drawing pre-processing for 3D reconstruction are presented in this thesis from the viewpoint of engineering application. It is more nicety and integrity than traditional method in pre-processing the information of engineering drawings through extracting and recognizing semantics information and half-cutaway view information. The scope of processing object is expanded from standard three views to actual engineering drawings, which expands applicability to 3D reconstruction radically. The algorithms in this thesis have been experimented in 3D reconstruction system and shown to meet the need of 3D reconstruction.更多还原