An approach for converting orthographic projection drawings into 3D-CAD models

Hand drawings and two dimensional(2D) CAD drawings have been replaced by three dimensional(3D) CAD models in mechanical design,but some 2D drawings produced before are needed in the new design.However,the techniques and software packages for automatically converting 2D drawings into 3D-CAD models with high precision have not yet been developed due to the difficulties to verify the validity of the drawings,to decide the hidden lines and concavo-convex faces,and to represent free-form surfaces.In addition,it is very time consuming to manually convert a large number of 2D drawings into 3D CAD models.To address these problems,we propose an approach for converting 2D drawings into 3D-CAD models automatically.     

Solid model reconstruction from engineering paper drawings using Genetic Algorithms

The wide applications of CAD/CAM technologies have promoted the development and application of many advanced technologies, such as digital manufacturing, rapid prototyping, enterprise resources planning, computer integrated manufacturing, concurrent engineering, virtual reality, and mass customization. These advanced technologies all need to be supported by three-dimensional (3D) solid models of products. Most enterprises, however, still organize their production using 2D paper drawings, which makes difficulties for the application of these advanced technologies. It is needed to convert engineering paper drawings into 3D solid models for applications. Based on holo-extraction of information from paper drawings, this paper develops a systematic 3D reconstruction method, which simulates an experienced human designer's thinking mode in transforming inaccurate outlines with inaccurate projection relationships in 2D drawings into 3D image, with the aid of Genetic Algorithms.     

ArchiDNA: An interactive system for creating 2D and 3D conceptual drawings in architectural design

We present an interactive system called ArchiDNA for creating 2D and 3D conceptual drawings in architectural design. We developed a novel principle of shape generation called match-and-attach by analyzing drawing styles of a contemporary architect, Peter Eisenman. The process consists of user interaction techniques and a set of rules that decide how one or more shapes attach to another shape. One key ingredient of our process is a unique concept for the interactive semi-automatic shape generation that uses the combination of algorithmic rules of a computer and designers’ manual inputs. These techniques enable designers to use CAD software in the early stages of architectural designs to explore conceptual building forms. ArchiDNA dynamically responds to drawing inputs, configures 2D shapes, and converts them to 3D shapes in a similar style. We intend to complement existing CAD software and computational drawing pipelines for intuitive 2D and 3D conceptual drawing creation.     

Holo-extraction of information from paper drawings for 3D reconstruction

The research on the conversion from 2D paper drawings to 3D computer feature models has been stuck in low-level coding. One of the reasons for it is that the three phases of understanding process has been isolated and people have been doing their research on only one of the phases since the whole conversion is very complicated and more difficult. For instance, the vectorization methods for the first phase were developed only for getting straight lines, arcs, circles, etc. so that much information contained in the drawing has been lost after the vectorization. This paper develops a holo-extraction method of information from paper drawings, the networks of single closed regions (SCRs), which can not only provide a unified base for recognizing both the annotations and the outlines of projections of parts, but also build the holo-relationships among SCRs so that it is convenient to extract lexical, syntactic and semantic information in the subsequent phases for 3D reconstruction.     

A new method for machining feature extracting of objects using 2D technical drawings

In this study, a new method called “3-Space” has been developed to obtain 3D models of prismatic machine parts using 2D technical drawings. This method uses 3 surfaces named Base, Top and Sweep Base for the determination of the objects. The edge colors have been given to the surfaces with meanings, and are used for the determination of the type and characteristics of the objects. 4 characteristics of the processing objects (namely external access direction, exit status, boundary geometry and the processing order of the features) have been determined. First, the object is considered a prismatic raw material, and the features to be processed on it are removed. Then the remaining object itself is created and thus a 3D view of the object is obtained.     

A complete system for the intelligent interpretation of engineering drawings

Converting paper-based engineering drawings into CAD model files is a tedious process. Therefore, automating the conversion of such drawings represents tremendous time and labor savings. We present a complete system which interprets such 2D paper-based engineering drawings, and outputs 3D models that can be displayed as wireframes. The system performs the detection of dimension sets, the extraction of object lines, and the assembly of 3D objects from the extracted object lines. A knowledge-based method is used to remove dimension sets and text from ANSI engineering drawings, a graphics recognition procedure is used to extract complete object lines, and an evidential rule-based method is utilized to identify view relationships. While these methods are the subject of several of our previous papers, this paper focuses on the 3D interpretation of the object. This is accomplished using a technique based on evidential reasoning and a wide range of rules and heuristics. The system is limited to the interpretation of objects composed of planar, spherical, and cylindrical surfaces. Experimental results are presented. Received December 2, 1998 / Revised June 18, 1999     

Automatic analysis and integration of architectural drawings

Recognition and integration of 2D architectural drawings provide a sound basis for automatically evaluating building designs, simulating safety, estimating construction cost or planning construction sequences. To accomplish these targets, difficulties come from (1) an architectural project is usually composed of a series of related drawings, (2) 3D information of structural objects may be expressed in 2D drawings, annotations, tables, or the composites of above expressions, and (3) a large number of disturbing graphical primitives in architectural drawings complicate the recognition processes. In this paper, we propose new methods to recognize typical structural objects and architectural symbols. Then the recognized results on the same floor and drawings of different floors will be integrated automatically for accurate 3D reconstruction.     

三维环境下的工程图自适应优化技术

工程图纸是企业生产的重要依据,对三维环境下的工程图纸进行优化以符 合企业的要求很有必要。论文利用模型与图纸的关联性,给出了以模型模板和工程图模板为 基础的自适应优化原理。提出了模板定制的原则,并给出了模板普通定制与特殊定制的方法, 为后续优化奠定基础。详细论述了实现自适应优化的几个关键技术,包括视图定位,比例匹 配,尺寸定位与明细栏优化,获得了大型复杂装配体工程图良好的优化效果。     

Skeleton-enhanced line drawings for 3D models

We present a novel line drawing approach for 3D models by introducing their skeleton information into the rendering process. Based on the silhouettes of the input 3D models, we first extract feature lines in geometric regions by utilizing their curvature, torsion and view-dependent information. Then, the skeletons of the models are extracted by our newly developed skeleton extraction algorithm. After that, we draw the skeleton-guided lines from non-geometric regions through the skeleton information. These lines are combined with the feature lines to render the final line drawing result using the line optimization. Experimental results show that our algorithm can render line drawings more effectively with enhanced skeletons. The resulting artistic effects can capture the local geometries as well as the global skeletons of the input 3D models.     

Reconstruction of 3D interacting solids of revolution from 2D orthographic views

3D CAD is replacing 2D CAD to improve efficiency of product design and manufacturing. Therefore, converting legacy 2D drawings into 3D solid models is required. CSG based approaches reconstruct solid models from orthographic views more efficiently than traditional B-rep based approaches. A major limitation of CSG based approaches has been the limited domain of objects that can be handled. This paper aims at extending the capabilities of CSG based approaches by proposing a hint-based recognition of interacting solids of revolution. This approach can handle interacting solids of revolution as well as isolated solids of revolution.     

Automatic generation of assembly plans from topological assembly drawings

An automatic understanding system MAD-READER based on the techniques of image processing, pattern recognition, and artificial intelligence has been developed for mechanical engineering drawings. The principles of the system are presented, which include the methods and techniques of recognition and understanding for topological assembly drawings (TAD). A rule-based generator GEN-PLAN is devised to generate directly assembly plans from TAD assembly drawings. A variety of TAD assembly drawings has been used for testing the generator. So far, GEN-PLAN has been used to recognize TAD assembly drawings which consist of 31 part symbols, and generate their assembly plans. The present generator has shown favorable results.     

基于采矿CAD的硐室参数绘图系统设计及实现

CAD系统因其本身具有许多长处,得到了工程设计人员的广泛使用。但它只能处理图形的几何信息,真正具有工程实际意义的图形拓扑信息和参数约束信息均被抛弃了。为了保留更多的图形信息以及让工程设计人员更方便地进行硐室图形的绘制,文中根据采矿CAD图形的特点,把要绘制的硐室图形进行参数化分析,并通过编程调用采矿CAD的接口实现了硐室图形的自动绘制系统。此系统能根据用户输入的参数自动生成硐室的二维和三维图形,这大大减少了设计人员的工作量,提高了设计效率,也有利于计算机辅助设计的进一步发展。     

An object-oriented progressive-simplification-based vectorization system for engineering drawings: model, algorithm, and performance

Existing vectorization systems for engineering drawings usually take a two-phase workflow: convert a raster image to raw vectors and recognize graphic objects from the raw vectors. The first phase usually separates aground truth graphic object that intersects or touches other graphic objects into several parts, thus, the second phase faces the difficulty of searching for and merging raw vectors belonging to the same object. These operations slow down vectorization and degrade the recognition quality. Imitating the way humans read engineering drawings, we propose an efficient one-phase object-oriented vectorization model that recognizes each class of graphic objects from their natural characteristics. Each ground truth graphic object is recognized directly in its entirety at the pixel level. The raster image is progressively simplified by erasing recognized graphic objects to eliminate their interference with subsequent recognition. To evaluate the performance of the proposed model, we present experimental results on real-life drawings and quantitative analysis using third party protocols. The evaluation results show significant improvement in speed and recognition rate.     

Mapping 2D midship drawings into a 3D ship hull model based on STEP AP218

Standard for the exchange of product model data (STEP) AP218 has a standard schema to represent the structural model of a midship section. While its schema facilitate the exchange of ship structural models among heterogeneous systems, most shipyards and classification societies exchange information using 2D paper drawings. We propose a feature parameter input method to generate a 3D STEP model of a ship structure from 2D drawings. We have analyzed the ship structure information contained in 2D drawings and have defined a data model to express the contents of the drawing. We also developed a GUI for the feature parameter input. To translate 2D information extracted from the drawing into a STEP AP218 model, we have developed a shape generation library and have generated the 3D ship model through this library. The generated 3D STEP model of a ship structure can be used to exchange information between design departments in a shipyard as well as between classification societies and shipyards.     

利用单元格和特征点实现图纸信息的自动提取

工程图中的标题栏和明细栏是产品数据集中管理的重要数据来源．出于重用CAD数据的考虑,提出了一种有效的工程图零部件信息提取方法．通过分析工程图中标题栏和明细栏的形式,从宏观布局和微观结构出发归纳了表格的位形特征;提出了基于单元格和特征点的图纸数据自动提取策略,详细介绍了算法思想和实施步骤;开发了实用程序并在工程项目中得到应用．     

Automatic form feature recognition and 3D part reconstruction from 2D CAD data

In this paper, a method which can recognize form features and reconstruct 3D part from 2D CAD data automatically is proposed. First, we use the divide-and-conquer strategy to extract the vertex-edge data from each 2D engineering drawing of IGES format. Then, a set of production rules are developed to facilitate the form feature matching process. A new structure of form feature adjacency graph (FFAG) is devised to record the related attibutes of each form feature. Finally, to avoid the combinatorial subparts composition problem, a sweeping operation and volumetric intersection approach is used to rapidly reconstruct the remaining 3D objects. The last reconstructed 3E object is used as the base of the FFAG. All the recognized form features in the FFAG can be classified as depression or protrusion features on the 3D part base. The FFAG structure can be easily transformed into CSG/DSG structure, which is readily integrated with the downstream CAPP/CAM systems. A detailed example is provided to illustrate the feasibility and effectiveness of the proposed system.     

Case Study of Developing Gear Pump Design System with SolidEdge

Part and Draft modules of SolidEdge are used to construct 3D solid models and generate part drawings, while ActiveX Automation of VB is used to access engineering database files to realize dimension-driven modification of the designed parts. Moreover, VB plays the enabling role of integrating all work processes of gear pump design, resulting in a comprehensive CAD system.1 Introduction SolidEdge is a 3D parametric design systemdeveloped by Intergraph and now acquired by UGSin U.S. It …     

Recovering solid geometric object from single line drawing image

Many educational materials contain a lot of solid geometric figures. The solid geometric objects in these figures are usually drawn as 2D line drawings thus have lost their 3D information. This paper presents a method to recover the 3D information of the solid geometric object from single line drawing image taken from the geometric books, which would be used to help the users better present and understand the solid geometric object on their mobile devices. The main advantage of our method is the abilitYTo handle inaccurately processed sketches as opposed to the previous methods which require perfect line drawings as inputs. Our method consists of three main steps as follows. First, the sketch of the input line drawing image is automatically extracted and further represented as an undirected graph. Second, candidate 3D models from the pre-built 3D model database are found by graph similarity-based searching and sub-graph isomorphism matching. Third, for each candidate 3D model, the model parameters, the rotation and the translation aligning the model with the sketch are found by minimizing an objective function which is composed of the residuals between the vertices of the sketch and the 2D projections of the candidate model’s vertices, and an optimal reconstruction solution is further selected as the final result. Extensive experimental results demonstrate the effectiveness and robustness of our method for recovering the solid geometric object from single line drawing image.