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31 October 2013, Volume 34 Issue 5 Previous Issue    Next Issue

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Progress of Digital Watermarking Technology for 3D Model Cui Hanguo, Liu Jianxin, Dai Xing, Zhou Zhixing 2013, 34(5): 1-5.  Abstract ( 107 )   PDF (407KB) ( 279 )   Digital watermarking technology has provided a copyright protection for 3D models at the network. The characteristics, classifications of the digital watermarks for 3D models and the techniques of attack to them are briefly illustrated. The present studies and functional evaluation of watermarks of all kinds including point clouds model, mesh model, parametric surface model and body data model are analyzed. The difficulties and matters of 3D model watermarking which need further study are finally concluded. Related Articles | Metrics

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The Design and Implement of Bridge Health Monitoring System Based on Internet of Things Zu Qiaohong, Zhang Haifeng, Xu Xingyu, Yin Ying 2013, 34(5): 7-11.  Abstract ( 76 )   PDF (829KB) ( 443 )   The research and application of Internet of Things (IOT) technology have been developed vigorously in various fields. Regarding to the hidden safety trouble of bridge health, a set of bridge health monitoring systems are designed and implemented based on IOT technology, which are verified by an example. IOT technology is adopted to realize real-time intelligent acquisition and transmission of the bridge structure’s arch rib deformation, abutment level relative displacement, abutment uneven settlement, girder deformation, cable force of the booms and bars, strain of the arch rib and girder and environmental information. A middleware software suite is developed to realizethe real-time receiving and storage of the bridge structure’s information. The visual monitoring software is used to realize remote monitoring and early warning, which provides the decision basis of the bridge monitoring, management and maintenance and guarantees the safe use of the bridge foundation facilities. A case analysis of the application of IOT technology in health monitoring of a river bridge is givenas a beneficial exploration. Related Articles | Metrics

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An Improved Delaunay Triangle Network Growth Algorithm and its Implementation Zhao Ting, Peng Zhenghong, Mi Xinwu 2013, 34(5): 12-15.  Abstract ( 82 )   PDF (798KB) ( 294 )   A brief introduction is given for the general Triangle network growth algorithm. An improved algorithm named as “the partition search method of the third point” is provided. First, a series of circular arcs are used to divide the area of discrete points into multiple partitions. Then - the third point is restricted to be searched only in the current partition and the next adjacent partition when building the triangle network. After all the discrete points are added into the triangle network in current partition, the search can be moved into the next partition. Last, the C++ programming language is used to test the algorithm in Microsoft Visual Studio 2008 environment. The result shows that the improved algorithm can improve the speed of building the network, and the generated triangular shape is good. Related Articles | Metrics

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An Auto-generating Method of Defect Distribution Mapping for Tank Floor Inspection Based on Magnetic Flux Leakage Song Xiaochun, Wen Haiyan, Xu Zhengwang 2013, 34(5): 16-19.  Abstract ( 101 )   PDF (830KB) ( 175 )   In order to solve the problem in defect distribution mapping for the current tank floor testing system, a method is developed based on the magnetic flux leakage (MFL) technique for generating defect distribution maps automatically for floor inspection. Firstly, the initial scanning position of the first channel sensor in MFL detector is chosen as reference point, and the single scanning region can be defined by sensor channel numbers and sampling interval; then the vertex coordinates of rectangle block diagonal are calculated by the sensor channels and sampling points of defect signals involved, a block can be drawn to characterize the defect and the single defect distribution map is generated. And after the reference point coordinates are normalized under an unified coordinate system, blocks characterized the same defect, which are drawn in two adjacent scanning, are merged into a new one by combing operation. Finally, the map to show defects distributed on the whole tank floor are joined by single defect distribution maps. The experimental results indicate that the proposed methods can generate the defect distribution map of tank floor automatically, provide defect reports for tank floor inspection intuitively, and improve the efficiency, practicality and reliability of the tank floor inspection system. Related Articles | Metrics

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Crank Speed Structure Design of Planar Linkage Du Li, Ren Hengbin, Huang Yonggang, Kang hualing, Fu Ting 2013, 34(5): 20-24.  Abstract ( 72 )   PDF (736KB) ( 218 )   In the design of crank connecting rod mechanism, in order to timingly adjust the distance from the crank to the center of the crankshaft, an innovative design of the crankshaft structure is given. Through the CAM slot with relative rotation disc in synchronous rotation, the planar linkage mechanism in the circumstance achieves the adjustment of the crank shaft eccentricity, and can bring crank which was realized using the middle CAM phase synchronous rotation. ADAMS simulation analysis shows that the structure can meet the needs of the stepless speed regulation system, the crank displacement and the original dynamic basic linear relation. Related Articles | Metrics

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Computer Simulation and Analysis of Wind Environment in Wuhan Urban Residential District Qian Yi, Shang Tao, Zhan Ping 2013, 34(5): 25-29.  Abstract ( 67 )   PDF (1382KB) ( 211 )   With the rapid growth of China’s urbanization, the wind environment of residential districts is getting people’s attention more and more. The winter windproof and summer natural ventilation are particularly important for Wuhan city which is hot in summer and cold in winter. This paper establishes the model of planning residential district by using software of Airpak3.0 and researches the relationship between the layout of building and wind by using   Turbulence model to solve the speed and pressure of residential district. The results demonstrate that computer numerical method can simulate the wind field accurately and wind environment is influenced obviously by the layout of residential district and inflow direction. Using numerical simulation method and reasonable building planning with the city wind rose can provide guidance and optimization of building planning construction for residential district in Wuhan area. Related Articles | Metrics

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Three-dimensional Computer Simulation of Sports Center Planning Design in Ezhou Chen Yonghong, Zhan Ping, Mi Xinwu 2013, 34(5): 30-34.  Abstract ( 95 )   PDF (994KB) ( 164 )   A visual three-dimensional computer simulation is conducted for the planning design of the new sports center in Ezhou. Ezhou Sports Center New digital elevation model data is obtained using aerial photographs to establish three-dimensional terrain model. The sports center topography is simulated by combing processed orthographic map of satellite photos as the map attached to the terrain surface. Modeling and post-production softwares are used to establish three-dimensional dynamic simulation of the planning design of the sports center. The results show that three-dimensional computer simulation used in the planning design is more suitable to communicate with the public and get more real, intuitive feedback than the traditional form of drawings and models. Related Articles | Metrics

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Learning of CAD/CAE/CAM Technology Step by Step An Ping, Wu Shusen, Ye Shenping 2013, 34(5): 35-39.  Abstract ( 95 )   PDF (1433KB) ( 232 )   According to the characteristics of CAD/CAE/CAM Technology and its adaptive in various courses, with such teaching and learning method as to study some contents in some certain courses, and to apply various knowledges in design combining with production practice, the students can master the CAD/CAE/CAM Technology during undergraduate period, and can become technicians with operation abilities. Related Articles | Metrics

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Embedding of Ship’s Engineering Drawing in Graphics Course in Navy Academy Ouyang Qing, Shi Guanyu, Mo Dengyuan 2013, 34(5): 40-45.  Abstract ( 93 )   PDF (877KB) ( 223 )   It is necessary to embed the ship’s engineering drawing into the graphics course for teaching of engineering drawing in navy academy. Based on analysis of the content and characteristics of the ship’s engineering drawing, the relations and difference between graphics and ship’s engineering drawing are discussed. A method embedding the dividing contents of ship’s engineering drawing into different contents of the graphics course is proposed. The graphics course system with navy equipment features will be set up. While the students study the theory and method of the graphics, their knowledge on ship’s engineering drawing will be developed and their capabilities on studying professional courses and fitting in with the needs of the post will be improved. Related Articles | Metrics

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Visualized Geometrical Demonstration of the Four Colors Problem and the Four Color Theorem of Simple Map Zhang Shiqing, Zhang Hao 2013, 34(5): 46-50.  Abstract ( 108 )   PDF (1270KB) ( 179 )   The arguments of the least colors that should be used to dye the 2D net color block graph, such as maps and patterns, have puzzled the academia for one hundred and sixty years or more. The basic reason is that the scholars have been working on to solve the problem with classical mathematics methods, even though it is not a classical mathematics problem. Visualized engineering geometry is used to turn the 2D net color block graph into dyeing equivalence normal map, and critically adjacent domain axioms proved. The smallest unit of maps and their dyeing mode is also established. Two kinds of map dyeing mode are found in the process. The first is simple dyeing mode, and the second is the relevant dyeing mode. At the same time, a visualized method is developed combining the dyeing and the process of turning the smallest map unit into maps together. It is proven critically that any simple maps are suitable for the least four colors dyeing method, but for the relevant maps, the number of colors that should be used are uncertain. Related Articles | Metrics

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3D Model Retrieval Based on Maximum Similar Category and Location Entropy Chen Junying, Meng Yuebo, Wang Xianhui, Liu Simei 2013, 34(5): 51-55.  Abstract ( 76 )   PDF (713KB) ( 212 )   For using descriptive information of individual feature of 3D models effectively, the maximum similar category of the query model is determined by comprehensively analyzing the distribution of models in retrieved results based on various features. Then the location entropy of the same class models of individual feature is calculated respectively. Finally, combination weights are computed dynamically based on the number of models of the maximum similar category and location entropy. Compared with other dynamic and static combination methods on Princeton 3D benchmark models, the results show the proposed method is effective in the case of weak features included. Related Articles | Metrics

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A Subdivision Algorithm for Non-uniform B-Splines of Arbitrary Degree Han Liwen, Yang Yuting, Qiu Zhiyu 2013, 34(5): 56-61.  Abstract ( 163 )   PDF (773KB) ( 255 )   A subdivision algorithm is presented for non-uniform B-splines of arbitrary degree in a manner similar to the Lane-Riesenfeld subdivision algorithm for uniform B-splines of arbitrary degree. The algorithm contains two steps: refining and smoothing, and achieves non-uniform B-Splines curve of arbitrary degree. The algorithm is based on blossoming rather than the continuous convolution formula for the uniform B-spline basis functions. Two blossoming polynomials are introduced to verify the correctness of the subdivision algorithm. The subdivision algorithm is more efficient than the classical uniform subdivision algorithm for B-splines of arbitrary degree, and as efficient as those currently available non-uniform subdivision algorithms for B-splines of arbitrary degree. Related Articles | Metrics

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The Similar Cutting Layers of Parabola and Elliptic Paraboloid Formed by two Projective Line Pencil Liu Fuping, Ding Yong 2013, 34(5): 62-65.  Abstract ( 81 )   PDF (717KB) ( 196 )   With drawing, a changing parabold is formed by the two projective line pencils formed. If the five vertexes of a pentagon are on a parabold, another parabold formed by a similar pentagon is similar to this one. In order to draw elliptic parabolaid using computer, a series of parallel cutting planes can be used which are similar parabolds to show the curves. This is referred to as cutting layers method. Related Articles | Metrics

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Offset Approximation of Loop Subdivision Surface Based on Weighted Progressive Interpolation Chen Tiantian, Zhao Gang 2013, 34(5): 66-70.  Abstract ( 116 )   PDF (881KB) ( 218 )   Offset plays an important role in the field of CAD/CAM. The offset approximation computation is more difficult for subdivision surfaces than parametric surfaces because subdivision surfaces have no analytical expression. The proposed approach is an improvement of two existed subdivision surface offset algorithms. Using the weighted progressive interpolation (WPI) method avoids the mesh deviation caused by the traditional methods. The boundary offset treatment is presented to obtain the uniform offset mesh. The proposed method avoids solving a linear equation system and has the advantages of both local and global methods. The method can be used to deal with either closed or open meshes. Offset approximation is an important operator to the applications of Loop subdivision surfaces in NC machining. Some typical examples are illustrated to demonstrate the efficiency of the proposed approach in the end. Related Articles | Metrics

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Triangular Bézier Curve of Order Two/Three Yan Lanlan, Han Xuli, Wu Guogen, Huang Guohui 2013, 34(5): 71-75.  Abstract ( 116 )   PDF (602KB) ( 205 )   Two sets of basic functions formed by triangular functions are constructed, and two new kinds of curves based on them are defined. We call them T-Bézier curve of order two and T-Bézier curve of order three respectively. They have the same simple structures with quadratic Bézier curve and cubic Bézier curve respectively. They have many properties of usual Bézier curve, such as convex hull property, symmetry, geometric invariance, endpoint interpolation and end edge tangent property. In addition, under the G1 continuity conditions, the T-Bézier curve of order two can achieve G3 continuity, and the T-Bézier curve of order three can achieve G2 continuity. Furthermore, the method of using the T-Bézier curve of order two to construct combination curve with given tangent polygon is also given. This method is simple and effective. The curve is conformal to the given polygon. Related Articles | Metrics

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Research of Key Technology in Process Plant Design Software Li Shicai, Tang Weiqing 2013, 34(5): 76-81.  Abstract ( 71 )   PDF (604KB) ( 207 )   The characteristics of business and design process are analyzed in process plant. The key technology and functional requirements of process plant design software is derived. Three key technologies of process plant design software are introduced. One is graphics platform technology, another is collaborative design, and the last one is life cycle management of process plant. The technology used in current process plant design systems is analyzed, and the difference between local plant design software and international plant design system are introduced. The suggestion for china’s future products is proposed at last. Related Articles | Metrics

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Model Construction and Simulation of Loader Steering System Based on Power Bond Graph Bian Xiangjuan, Gong Youping, Li Zhihua 2013, 34(5): 82-87.  Abstract ( 67 )   PDF (5130KB) ( 207 )   To satisfy the motility, agility and security of the loader in making truing in limited domain through the design of its steering system, the common way is through virtual simulation design. The working characteristic of the loader steering system is firstly analyzed, including system structure, working principle and system simplify model. Then, the power bond graph of the steering hydraulic system is constructed through bond graph tool according to energy and information transformation. Also, the equation of state is deduced by the power bond graph. A hydraulic steering system simulation model is constructed in MWORKS software, and simulated steering working process. The completed theory and method of little type multifunctional loader are offered. It is not only significant in theory, but also very valuable in practice. Related Articles | Metrics

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Research on the Practice Instructing for the Product Design Curriculum Under the University-Industry Collaboration Mode Liu Yongzhan, Liu Jinghua 2013, 34(5): 88-92.  Abstract ( 106 )   PDF (720KB) ( 289 )   The product design curriculum is core for the industrial design education system. Aiming for the problem of students’ lack of practical ability, the university-industry collaboration mode which can utilize the advantages of both sides would combine the theoretical school education with practical producing process. By implementing various ways of instructing and interaction, and separately using the rich experience of the early, mid and later stage in product development from enterprises, the students’ key ability of concept creativity, forming designing and product realization can be effectively improved. Related Articles | Metrics

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A Design Method of Automobile Front Face for Users’ Cognizance Zhang Yue, Lu Zhaolin 2013, 34(5): 93-98.  Abstract ( 124 )   PDF (5932KB) ( 209 )   In order to form the characters of auto front face of product family for emerging independent companies, a design method for users’ cognizance is proposed to enhance the awareness of consumers. The definition of auto front face and the conception of product family are discussed. The specific design process is divided into Gestalt design, visual characters design and details design. Furthermore, how to utilize the characters of front face in product family is explained. Finally, taking Buick as a case, the method is described. Related Articles | Metrics

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The Calculation Methods for First Warp Model Frequency of Double-shell Aluminum Alloy Carbody Zhao Shui, He Xin, Yuan Xin 2013, 34(5): 99-102.  Abstract ( 64 )   PDF (491KB) ( 171 )   Model Frequencies of carbody structure are the important parameters in the design of rail vehicles. In order to assure the first warp model frequency that is above 10Hz during the design phase, the formulas is derived, and FEA proceed. Then the results are compared with each other and the reasons for the difference between them are concluded. The calculation is useful for the design of carbody structure. Related Articles | Metrics

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Virtual Angioscope System Based on Fusion of Coronary Angiography and Intravascular Ultrasound Images Sun Zheng, Han Shaoqin 2013, 34(5): 103-109.  Abstract ( 107 )   PDF (909KB) ( 186 )   An interactive virtual angioscope system for coronary arteries based on X-ray coronary angiograms and intravascular ultrasound images is constructed. First, the vessel including lumen and possible plaques is three-dimensionally reconstructed through fusion of both types of image data. Then, visualization of the 3D vessel model is implemented in the manner of endoscopic fly-through with virtual reality modeling language. Such a virtual coronary angioscope system can be used in the diagnosis of coronary artery diseases, in the study on the development of atherosclerosis, in the evaluation of interventional treatment and in the training of medical personnel. Related Articles | Metrics

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Application of Improved BP Neural Network in Hyper-spectral Image Compression Yan Hongmei, Wu Dongmei 2013, 34(5): 110-114.  Abstract ( 78 )   PDF (1356KB) ( 234 )   The hyper-spectral image compression is focused on compression quality and time owing to the application fields of hyper-spectral image. The application of BP Neural Network in the hyper-spectral image compression can get better compression quality. A joint-optimized improved algorithm on the premise of good renewed qualities is presented. It uses Cauchy error estimator and shape factor in Sigmoid function, upgrades the differential coefficient and each lay adapts different step adjustment. Simulation results prove that the algorithm can reduce compression time and improve coding efficiency. Related Articles | Metrics

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A Method for Detecting Fruiter Crown Diameter in Variable-rate Spray System Shen Mingming, Zhang Fugui, Wu Xuemei, Liu Guozhi, Chen Yuyi 2013, 34(5): 115-120.  Abstract ( 73 )   PDF (467KB) ( 182 )   A variable-rate spray system of fruiter needs real-time detection for the fruiter crown diameter. Existing digital image processing technology can not realize real-time detection for the fruiter crown diameter. The problem is that the detection error is large or no error can be detected. A reference standard plate with fruiters when capturing images is used to obtain the fruiter crown diameter by calculating image unit pixel width in this paper. Comparing with the reference crown diameter detected by the handheld laser rangefinder, test results show that 74% of the test sample of 50 fruiters have a relative difference of less than 20% between the crown diameters detected by the image processing method and the reference values. The regression analysis of fruiter crown diameter on digital image detection value and the reference one shows R2=0.7406. Related Articles | Metrics

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Product Selection and Customization System Ye Jianhua, Gao Chenghui, Jiang Jibin 2013, 34(5): 121-125.  Abstract ( 69 )   PDF (568KB) ( 329 )   A selection and customization system is presented for mechanical design. 3D parametric model of product is created by SolidWorks. The parametric model is deformed by API of Solidworks to meet customer's requirement. This system uses the Viewpoint technology to display the 3D model and allow user to download 2D or 3D mode. The prototype system is developed and the results are reported. This system can meet the tacks of design. Related Articles | Metrics

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A Technique for Virtual Human Calibration Based on Optical Motion Capture Hou Yonglong, Ning Tao, Wang Ke 2013, 34(5): 126-131.  Abstract ( 86 )   PDF (773KB) ( 218 )   Based on optical motion capture, two joint center estimation models: Bi-segment Model and Sphere Model are given by analyzing the motion of segments constrained by joints. For each model a least squares solution is presented respectively and the joint center location could be acquired by solving a linear equation. A virtual linkage is used to test the accuracy of the two least squares solutions. Using the Bi-segment Model which is more accurate, a technique for virtual human calibration is proposed based on the topology of the virtual human. The comparison of measured values and calibrated values of a performer demonstrates errors for limbs are less than 4.3%. Finally, the calibrated virtual human is driven. The result shows the virtual human can mimic the performer vividly and limbs intersection cases are reduced. Related Articles | Metrics

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Research on Graphical Engineering Statics Lin Dajun 2013, 34(5): 132-137.  Abstract ( 56 )   PDF (715KB) ( 271 )   The fundamental principle of orthogonal projection can be used to solve problems that arise in the field of engineering statics. This paper deals mainly with the graphical solution of elementary, concurrent force and forces in space problems. Some actual examples are included to illustrate applications of the simple principles and will encourage further study. Most problems in engineering statics can be solved by either graphical or algebraic methods. In some cases the algebraic solution is more readily obtained. In other cases, the graphical solution is quick and more economical. In a number of cases AutoCAD solutions may be well justified. Related Articles | Metrics

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Rapid Three-Dimensional Annotation Based on GB/T 24734 Xu Jinglin, Zheng Guolei, Wang Bo 2013, 34(5): 138-142.  Abstract ( 87 )   PDF (655KB) ( 286 )   Current mainstream commercial CAD software still has functional limitations that can’t meet the requirements of manufacturing enterprises. To realize the annotation of parts, especially parts with complex features, the rapid annotation of 3D model in CAD system is investigated based on the standard GB/T 24734. A rapid 3D annotation algorithm is proposed, and the relevant technology is illustrated in detail. The procedures of rapid annotation mainly deal with the auto-construction of annotation plane, the computation of dimension elements, and the processing of annotation results. The classification of annotation plane and the cursor point transformation are introduced to automatically construct annotation plane. All the annotation results are handled to display in a forward direction. All the algorithms presented are realized and the verification is conducted on the CATIA V5 system. The results prove that the proposed 3D rapid annotation algorithm performs well. Related Articles | Metrics

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Research and Application of Finite Element Modeling Strategy for Mechanical Equipment Metal Structure Zhu Huiwen, Huang Qiliang, Wang Zongyan, Qu Xiaozhang 2013, 34(5): 143-147.  Abstract ( 85 )   PDF (587KB) ( 179 )   Based on the analysis of research status and limitation of finite element modeling technology, in view of the characteristics of mechanical equipment’s metal structure, such as large volume, complex structure, in order to establish the finite element model quickly and accurately, the framework of finite element modeling strategy is established, and eight strategies which should be followed in the finite element modeling process is put forward. The eight strategies mentioned above include global planning, equivalent synthesis, real time check-up, equivalent substitution, discretionary weakening, reasonable simplification, key refinement and skilful use of interference. In addition, taking ladle crane as an analysis object, the above modeling strategy is illustrated and the effectiveness and applicability of them are validated. Related Articles | Metrics

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Structuralization of Similar Planes on the Views Dong Ping 2013, 34(5): 148-153.  Abstract ( 74 )   PDF (717KB) ( 225 )   The similar vertical plane of projection plane and the similar incline plane on the views are studied respectively. Two situations are discussed. One is when the contour line of the similar same plane can be constructed, and the other is when it can not be constructed. In either situation, the planes are both constructable. Related Articles | Metrics