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29 June 2013, Volume 34 Issue 3 Previous Issue    Next Issue

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A Ray Tracing Method Based on the Nearest Points Cai Peng, Yin Baocai, Kong Dehui 2013, 34(3): 1-6.  Abstract ( 94 )   PDF (567KB) ( 185 )   This paper presents a ray tracing method based on the nearest points. Based on rude point clouds, we employ a balanced binary tree to locate the nearest N points in setting range, and employ grid structure to avoid unnecessarily iterative computation in point clouds space. The intersecting computation is done between ray and local plane. To the actual nearest N’ points, the normal of local plane is computed by triangle-area-weighted average computation of normals of corresponding triangles, and we ensure coherence of computation of normal. Our method can progressively render rude point clouds in multi-resolution mode by changing ray tracing parameter (number of nearest points), and we set bigger number of nearest points to effectively remove noise of rendering for point clouds with many noises, and we set smaller number of nearest points to show more local geometry character for point clouds with less noise. Related Articles | Metrics

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Improved Morphological Watershed Algorithm to Enhance Image Detail and Denoise Ability Guo Hong, Zhang Qingzhi 2013, 34(3): 7-11.  Abstract ( 95 )   PDF (520KB) ( 299 )   An improved morphological watershed algorithm is presented to solve the over-segmentation of watershed and keep the image detail. First, the image is decomposed by multi-scale wavelet into high-frequency and low-frequency coefficients. The low frequency coefficient of the image is filtered by Anisotropic diffusion filter algorithm based on Perona-Malik diffusion model. The high frequency coefficient of the image is enhanced and denoised by using the improved adaptive Genetic Algorithm, which is gotten by introducing the sigmoid function in neural network to modify the generation of the mutation and crossover probability, and by replacing the worst individual of the children with the best individual of the father generation to protect the best individual from being destroyed, and to overcome the local optimal phenomenon of genetic algorithm. Then, the gradient image is sharpened to highlight the edge, the watershed algorithm is applied after conducting the morphological operation and the H-minima label on it, the improved algorithm is realized. Experiment shows that the improved algorithm can significantly restrain the noise disturbance and reduce the over-segmentation, and its segmentation accuracy is also improved. Related Articles | Metrics

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Selection and Reduction Algorithms for Large Point Clouds Fan Ran, Jin Xiaogang 2013, 34(3): 12-19.  Abstract ( 67 )   PDF (535KB) ( 344 )   Selection and reduction for large point clouds are the indispensable post-processing steps to deal with the problem of background data, redundant sampling and non-uniform distributions. Traditional methods still have many limitations for custom low cost 3D scanning system. There is no public available point cloud selection algorithm supporting lasso UI interfaces in research community; traditional point cloud reduction algorithm focuses on adapting samples to surface curvature without considering balanced distribution in flat regions. This paper presents a new point cloud selection algorithm with lasso UI interfaces, which avoids most of the point-in-polygon tests by constructing rectangle covering of the lasso polygon and the octree encoding of the input point cloud. Based on Poisson-disk sampling, a novel point cloud reduction approach is proposed, in which the radius of the disk embedded on surface is defined by Boolean intersection between neighborhood spheres of samples resulting in the property of sharp edge feature preserving. The experimental results demonstrate that these methods provide satisfactory results for point cloud removal preprocessing in low cost 3D scanning system. Related Articles | Metrics

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A Robust Zero-Watermark Algorithm in Hybrid Transform Domains Based on Subsampling Han Shaocheng, Zhang Zhaoning 2013, 34(3): 20-24.  Abstract ( 113 )   PDF (710KB) ( 212 )   A novel zero-watermark algorithm is proposed based on subsampling in hybrid transform domain for the copyright protection of image dates. In this method, the host image is performed with Non-Subsampled Shearlet Transform (NSST) firstly, and low-frequency component is divided into four sub-images by subsampling, then block processing is done to every sub-image. Finally, the zero-watermark is constructed by judging the numerical relationship between the DC coefficients of two special blocks from different sub-images randomly. Experimental results show that the method is very robust to common attack operations such as Adding noise, JPEG compression, Cropping and so on. Related Articles | Metrics

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An Interactive Isoline map Vectorization Method Jia Yu, Wang Ying, Yao Xingmiao 2013, 34(3): 25-28.  Abstract ( 102 )   PDF (446KB) ( 222 )   Isoline map vectorization has been widely used in geology, geophysics, geographical information systems, etc. There are still some shortcomings of the computer automatic recognition in practical application. This paper presents an interactive isoline map vectorization algorithm by improving the isoline map vectorization algorithm based on the circular track. The isoline intervals tracking algorithm makes up for the shortcomings of computer automatic recognition by manual intervention, ensures the correctness of the tracking, fits for the grayscale isoline image vectorization. This algorithm is practical and efficient. Related Articles | Metrics

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Exponential Uniform B-Spline Curves and Surfaces with Multiple Shape Parameters Zhang Li, Liu Jingjing, Tan Jieqing 2013, 34(3): 29-35.  Abstract ( 78 )   PDF (567KB) ( 239 )   A class of exponential uniform B-spline curves and surfaces with multiple shape parameters is provided. They preserve the main properties of the exponential uniform B-spline curves and surfaces, such as positive property, convexity-preserving property and so on. The curves can be adjusted by changing the values of shape parameters without moving their control points. So we can realize the entire or local adjustment of the curves. What’s more, the exponential uniform B-spline curves can represent hyperbola, catenary and other transcendental curves precisely. The corresponding surfaces can be constructed by using tensor product, so their properties are similar to that of the curves. Plenty of numerical tests are given to show the effectiveness of our method. Related Articles | Metrics

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B-spline Curves and Surfaces Extension with Constraints Xu Jin 2013, 34(3): 36-42.  Abstract ( 86 )   PDF (371KB) ( 233 )   An algorithm for extending B-spline curves with a sequence of ordered points constraint is presented based on the curve unclamping algorithm. The most important feature of this algorithm is the ability to optimize the knots of the extended curve segment according to the ordered points. Thus, with minimum number of interpolation points, the maximum deviation of the extended curve segment from the ordered points is less than the given tolerance. The extended curve segment connects to the original curve with maximum continuity intrinsically. Further more, this algorithm can be applied to the extension of B-spline surfaces with the constraints of a sequence of B-spline curves. Several experimental results have shown the validity and applicability of the proposed algorithm. Related Articles | Metrics

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Generation Method of B-spline Parametric Volumes for Isogeometric Analysis Xu Huaqiang, Xu Gang, Hu Weihua, Wang Guozhao 2013, 34(3): 43-48.  Abstract ( 132 )   PDF (430KB) ( 451 )   Volume parameterization is the key step in three-dimensional isogeometric analysis. In this paper, we propose discrete Coons method for B-spline parametric volume generation from given boundary surfaces. The parametric formula of Coons volume interpolating the boundary surfaces is firstly presented. From the discrete version of this formula, for B-spline volume generation, the inner control points can be obtained by the linear combination of the boundary control points. Furthermore, the discrete coons mask is generalized into a unified form in the mask, which provides various choices for the generation of inner control points. The volume parameterization obtained from different mask and their influences on the result of isogeometric analysis are also compared by an example for heat conduction problems. Related Articles | Metrics

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3D Converse Modeling for Sphere Point Cloud Li Shengnan, Lin Xiao, Chen Yan, Ma Lizhuang 2013, 34(3): 49-52.  Abstract ( 67 )   PDF (335KB) ( 201 )   Sphere fitting is one of the complex and waiting prompt solution problems in the field of 3D Converse Modeling, which can be used for the parts detection, the recovery of the architecture, medicine and so on. The paper offers a method to directly fit sphere, called DF algorithm, and acquire the geometric parameters with improvement at speed and accuracy. The paper also pays attention to data analysis for the cause of the results and the comparison with the LM (Levenberg-Marquardt) algorithm, which is the one of the most widely used nonlinear least square methods, laying foundations for the rebuilding the parts and the gives of the further work. Related Articles | Metrics

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Research on the Characteristics Embodied in Ancient Chinese ArchitectureSimilar to Those of Modern Industrial Products and their 3D CAD Representation Zhang Shijie, Xiang Bingzhe, Zhang Yuanqing, Yang Zhun 2013, 34(3): 53-57.  Abstract ( 82 )   PDF (830KB) ( 232 )   This article deals with the characteristics embodied in the frame construction of ancient Chinese architecture. The characteristics discussed here include the concept and methods of parts-assembly design, modularization design, and seriation design. It also discusses the 3D representation of ancient Chinese architecture. Related Articles | Metrics

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Automatic Generation of Corner Machining Program for Planar Profiles during Post-processing Rao Youfu, Zheng Guolei, Chen Jun1 Du Baorui, Chu Hongzhen 2013, 34(3): 58-64.  Abstract ( 75 )   PDF (455KB) ( 172 )   To solve the problem of early NC programs lack of corner processing, an algorithm about corner recognition and automatical generation of processing program for planar profiles around NC code is proposed. This method can meet the product upgrades and high processing requirements of NC machining, and further ensure the security and the surface quality of parts. Firstly the common NC code structure is summed up. Secondly the NC Code geometry representation is expressed as edge chains. Then the direction of those chains and the edge tangent in chains are computed. And the corners are classed as point and arc corners. At the same time, the recognition rules of corner, considering these factors such as discrete structure of arc corner and closure of chains, are presented. To reduce the instantaneous cutting amount of processing at the corner position from the tool axis, Corner machining is layered. Each layer of corner processing tool path consists of feeding, cutting in, corner processing, cutting out and retracting sections. Layers of path are connected with feeding-retracting lines. Finally, an experimental result is showed to prove this algorithm. Related Articles | Metrics

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A Generic Method of Measuring Points Accessibility Analysis for Coordinate Measuring Machines Zeng Debiao, Zheng Guolei, Zeng Chunling 2013, 34(3): 65-71.  Abstract ( 67 )   PDF (424KB) ( 203 )   The accessibility of measuring points has to be analyzed before contact probing with coordinate measuring machines (CMMs) to avoid collision and provide accessible orientations for the determination of measurement orientations. This paper proposes a generic accessibility analysis algorithm for common styluses. Users construct interactively the models of styluses, probes and other CMMs components. Inaccessible orientations of measuring points are excluded fast according to the kind of stylus tip. Then, the static and dynamic accessibility of measuring points in each measurement orientation is analyzed through computing the minimum distance between CMMs components and barriers such as workpiece and fixture. All accessible orientations of measuring points are obtained accordingly. Because barriers are discretized for accessibility analysis, this method is suitable for any complicated workpiece. Related Articles | Metrics

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Research on Process Model and Framework of Collaborative Design for Complex Product Based on Meta-synthesis Zhou Jian, Xiao Fu, Tang Haofeng, Tang Weiqing 2013, 34(3): 72-78.  Abstract ( 68 )   PDF (526KB) ( 171 )   To express the design process effectively by establishing the process model and framework is the foundation of collaborative design. According to the features of design process for complex product, a multi-level process model of collaborative design for complex product based on the dimensions of time, particle size and parallelism is established, combining with meta-synthesis. This process model emphasizes on the combinations of multi-stage in time dimension, combinations of multi-specialty in parallelism dimension and iteration of decomposition and integration in particle dimension. Then, on the base of the process model, a process framework of collaborative design for complex product based on meta-synthesis is proposed, combining with expert system, knowledge system and machinery system. Machinery system helps the expert group with knowledge from knowledge system. Expert system fulfills the collaborative design process of combinations of human-computer, multi-specialty and multi-stage, with the services provided by machinery system, e.g. project management, group argumentation, collaborative decision and 3D visualization. Finally the prototype system which has been developed based on the idea of this paper is introduced. Related Articles | Metrics

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The Method Study of Harmonizing Colors in Product Based on Genetic - Ant Colony Algorithm ZhangYan, Yu Suihuai, Chen Dengkai, LiuSheming 2013, 34(3): 79-84.  Abstract ( 101 )   PDF (368KB) ( 187 )   The method combines the advantages in optimization grouping of genetic algorithms and ant colony algorithm, and blends it into the product color combination design of industrial design. Firstly, the whole color program libraries is searchedby using genetic algorithms to produce the original solution set of relevant issues. Then the characters of ant colony algorithm such as parallelism, mechanism of positive feedback and high sufficient solving problems are used to obtain the optimal solution. Finally, the color combination design of tank truck vehicle is taken as an example to proceed color optimization design, and access the result with fuzzy evaluation. The effectiveness of the method is proved. The method overcomes the defects of two algorithms, absorbs their advantages, and improves the efficiency of product color combination design and the intelligent design level. Related Articles | Metrics

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The Function Orientation and Creative Ideas of Robotic Chair/Bed Based on Step-down User Research System Jiang Qian, Liu Jinghua, Chen Diansheng 2013, 34(3): 85-89.  Abstract ( 49 )   PDF (357KB) ( 267 )   This article presents the Step-down user research system combining with several parallel user research methods, and gets a deep understanding of users with this system in the project of robotic chair/bed. The product’s initial function orientation and creative ideas are fomed by translating the user need into product need. In this system, a new method of user research is creatively put forward to get the latent demand more accurately using personas and scenarios. Related Articles | Metrics

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Research on the Innovative Design Method and Characterization for Industrial Design Based on Basic Element Model Liu Lingling, Xue Chengqi, Li Jing, Lin Li 2013, 34(3): 90-94.  Abstract ( 54 )   PDF (261KB) ( 231 )   Directed to features of creative thinking for industrial design, constructing the basic element model for innovative design is presented to meet the formalized, efficient idea-forming-process target for breaking the Inspiration generation "Black Box". Using the theory of extension basic element, the method of creative design and the characterization is proposed, which concludes the conception methods from four points of Special features，Special attributes， Special rules and Relations isomorphism. Then, the points for the matter-element acquisition are cleared to promote the core quality of the innovation effectively. Finally, taking the Household humidifier design as an example, the effectiveness, practicality and innovativeness of the method is verified. Related Articles | Metrics

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Approach to Shot Segmentation Based on Automatic Decision of Feature-Point Number Li Guohe, Liu Dianxing, Zang Jinxiao, Wu Weijiang 2013, 34(3): 95-99.  Abstract ( 74 )   PDF (354KB) ( 174 )   Shot segmentation is very important for video retrieval based on image content. In order to improve the performance of shot segmentation, Harris operator is adopted to evaluate the energy of image pix, and exclude pseudo feature points. By means of partition of frame in the video into blocks and edge detection of the blocks, the minimal feature-point set is obtained and the feature points are made relatively well-distributed. And then according to the feature points, statistical quantity of frame in video is computed to construct feature vector to express the frame. Based on above, along with gradual transition detection and flash detection of frame, a method of shot segmentation is presented. Experiments of shot segmentation are efficient. Related Articles | Metrics

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Test of inside- and outsidePolygon Points in 2D Graphic Engine Yang Yuting, Kang Houliang 2013, 34(3): 100-105.  Abstract ( 65 )   PDF (367KB) ( 203 )   In 2D graphic engine, visibility determination is very important. Through screen clipping, it can reduce the quantity of polygon and ease the burden of the engine. So the screen point inclusion test for planar polygon is important in screen clipping phase. In combination with the 2D graphic engine characteristics, the popular algorithm is provided in DirectX platform using c++ to implement test of inside- and outside-polygon points, and it is applied in 2D graphic engine. The algorithm is proved to be simple and effective. Related Articles | Metrics

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Numerical Simulation of the Movement of Materiel Particles on the Transfer Station Piao Xianglan, Guo Yue 2013, 34(3): 106-110.  Abstract ( 82 )   PDF (234KB) ( 218 )   To analyze the movement of materiel particles on the transfer station, the interaction between particles, interaction between particles and boundaries and the energy terms in the movement process, the procedure of particle flow code(PFC3D) based on discrete element method (DEM) is used to build the discrete element model of the transfer station. Numerical simulation of the materiel Particles is directed towards the different velocities of the particle flow and whether there is a baffle in front of the roller or not. By means of simulation, it is found to have some advantages: (1) The solid particles’ motion can be followed better (the position, velocity, average contact force and average unbalance force of each particle). The maximum of the average contact force increases along with the increase of particle’ velocity, but the average unbalance force has little change; (2) Following the course of the energy, the transformation of various kinds of energies can be looked into; and in all kinds of energies, kinetic energy varies most; the baffle will carry weight to kinetic energy, friction energy and strain energy. Related Articles | Metrics

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An Experimental Study of Chatter Caused By High Speed Empty-Cutting of Thin Rib Xu Dongmei, Sheu Jinnjong 2013, 34(3): 111-114.  Abstract ( 81 )   PDF (381KB) ( 187 )   The processing quality of accessories, coarseness of their surface, and service life of cutting tools are affected by chatter caused by high speed empty-cutting of thin rib. In order to overcome those influences, the dynamics of thin rib amplitude was analyzed without direct exciting vibration from external force during empty-cutting, then finite element method and Taguchi experiment were applied to conduct simulation experiment and dynamic displacement exciting vibration on the thin rib. It was proved that the width, height and thickness of thin rib directly affected its displacement. The displacement of thin rib was decreased with increase of its width at a certain height, while increased with decrease of its thickness at a certain width and height. Meanwhile the displacement of thin rib was increased with increase of its height at a certain width and thickness. Furthermore, the dynamics of energy in the thin rib during its dynamic displacement was explored, and the time for complete attenuation of its energy was obtained. Accordingly the processing path of thin rib was designed to avoid chatter. Related Articles | Metrics

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Digital Design and Simulation Analysis of Individual Fixed Steel Plates of Femoral based on CT Image Liu Yang, Tang Chao, Lin Hua, Liu Yang, Tang Chuanling 2013, 34(3): 115-119.  Abstract ( 125 )   PDF (430KB) ( 203 )   Based on the CT scans, the three-dimensional model reconstruction of the femoral fracture site is completed and a new concept, design procedure and fixation method about femoral fracture internal fixation is proposed, which is individual fixation plate. The virtual assembly of fixation plate is conducted in Solidworks, and the finite element simulation analysis of statics is implemented in Ansys12.0. The data show that its static properties have been improved greatly compared to standard fixation steel plate. Because of high adaptability with the femur surface and joint degree which comfort the patients, this method has some practical reference significance for the bone surgery. Related Articles | Metrics

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The Initial Research on the Digital Simulation and Synthesis of Yunnan Out-of-print Woodcuts Li Qian, Xie Wanyu, Li Yurun, Pu Yuanyuan, Xu Dan 2013, 34(3): 120-125.  Abstract ( 82 )   PDF (914KB) ( 185 )   Non-photorealistic rending (NPR) has already become one of the most active research topics in current computer graphics domain. NPR, which is established on human cognition, takes advantage of computer to generate various artistic graphics. Yunnan out-of-print woodcuts are the typical representative of Yunnan local minorities’ characteristic painting. Through exploring and analyzing its actual creation process, we reveal its feature and laws in creation techniques and in the usage of strokes, texture and color, which is crucial for us to explore and research the key techniques of Yunnan out-of-print woodcuts’ digital simulation and synthesis based on image. Based on the research described above, this paper primitively explores and implements the scratch simulation and synthesis based on Line Integral Convolution, color-mixture based on multi-frequency noise LIC textures and texture synthesis of the scratch. Related Articles | Metrics

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A Portrait Generation Algorithm of Yunnan Heavy Color Painting Lu Liwen, Pu Yuanyuan, Liu Yuqing, Qian Wenhua, Xu Dan 2013, 34(3): 126-133.  Abstract ( 81 )   PDF (835KB) ( 297 )   A portrait generation algorithm of Yunnan heavy color painting is presented in this paper. First, the painting characteristics of Yunnan heavy color painting are summarized by extracting facial features from Yunnan color painting works and calculating the proportion between facial features. Second, the extent to deformation is calculated by comparing features of real face and painting characteristics and the real face is deformed. Finally, the positions of eyes, the nose and so on are adjusted according to subjective experiences. The portrait generated by this algorithm is similar to the original picture and fits the distribution feature of facial characteristics of Yunnan heavy color painting. Related Articles | Metrics

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Thinking Based on Students Mapping and Modeling Innovation Competition Li Huaijian, Wang Jianping, Zhang Qi, Huang Chuan, Wang Hao 2013, 34(3): 134-137.  Abstract ( 67 )   PDF (349KB) ( 231 )   In order to further promote the reform of the engineering graphics teaching method, this paper introduces the students mapping and modeling innovation competition and discusses the meaning of the national university generating graphics and modeling innovation contest and the problems found in the competition. The paper elaborates that expounding the engineering graphics curriculum theory teaching and practice are two important factors of cultivating outstanding engineers. It puts forwards the idea of using the national university mapping competition as a guide to build new teaching concepts, new teaching contents and new teaching assessment so as to adapt to the trend of outstanding engineers and engineering education training reform and prompt the school to further develop practical ability in the overall project. Related Articles | Metrics

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American Specialized Accreditation in High Education and Graphics Education Xu Tenggang 2013, 34(3): 138-141.  Abstract ( 50 )   PDF (194KB) ( 225 )   In the United States, accreditation is a non-governmental, peer-review process that assures a college or university program to meet the quality standards established by the profession for which it prepares its students. ABET, Inc., is responsible for the specialized accreditation of educational programs in applied science, computing, engineering, and technology. St. Cloud State University is an example to show the relationship between its teaching work and accreditation. Related Articles | Metrics

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Cultivation of High-skilled Creative Talents on Deepening Teaching Reform of Mechanical Drawing Song Hongxia 2013, 34(3): 142-147.  Abstract ( 87 )   PDF (552KB) ( 350 )   The Worldskills International and the basic situation about China's first participation in the worldskills competition are introduced briefly. The competition projects of mechanical engineering design CAD are illustrated in detail to let people learn more about it, which will help the reevaluation of the teaching objectives of mechanical drawing and the key teaching points so as to further push China's mechanical drawing teaching to link with the international competition as early as possible, as well as fostering high-skilled innovators. The purpose of the study is how to cultivate high-skilled creative talents based on deepening teaching reform of mechanical drawing by its characteristics. Thus some common and pressing problems in the course teaching are analyzed deeply and the corresponding approaches are put forward clearly. Related Articles | Metrics

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Reconstruct Curriculum System of Engineering Graphics Based on CDIO Guo Changhong, Zhao Bingli, Guo Rui, Wang Wei 2013, 34(3): 148-151.  Abstract ( 68 )   PDF (214KB) ( 267 )   This paper introduces the present situation and insufficiency of the engineering graphics teaching. Based on years of the engineering graphics teaching reform experience，the paper briefly introduces how to reconstruct curriculum system of the engineering graphics based on CDIO. The practice shows that such a teaching model is very effective to inspire and cultivate students’ practical ability and creativity. Meanwhile, it has also laid a good foundation for the follow-up courses, graduation design, and even future research work. Related Articles | Metrics

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Thinking on Architectural Teaching Based on Digital Graphics Technology Li Kun 2013, 34(3): 152-156.  Abstract ( 70 )   PDF (204KB) ( 166 )   Architecture has closed relationship with engineering graphics and has double requirements of artistry and precision. Improving architectural teaching quality using digital graphics technology during the teaching process is becoming essential approach. Principle and teaching method of digital graphics technology in the architectural teaching is deeply researched and their combination mode in the future is expected based on the relationship analysis between digital graphics and architectural teaching course. Graphics education needs adaptive evolution supported by new digital technology and combined with education of architecture. It would be the way to display the superiority of graphics expression, which has the meaning of teaching and practice. Related Articles | Metrics

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Intelligent Fault Diagnosis of Diesel Engine Based on Structure and Behavior Zhang Tong, Han Jing, Liu Ping 2013, 34(3): 157-161.  Abstract ( 84 )   PDF (518KB) ( 194 )   Intelligent Technique of Fault Diagnosis is a new fault analysis, which pays more attention to doing research on the overall structure of the system and transmission relationship between the different faults. Structure and behavior-based diagnosis is a thought breakthrough in the intelligent diagnosis. It is a kind of model-based diagnosis. Modeling, diagnostic generation and diagnostic tests are studied in depth and a diagnostic system which can be applied to the actual production system is brought out. Then it is applied to the fault diagnosis of the intake system of diesel engine. Related Articles | Metrics

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Computer-aided Graphics Reading System Wu Zhanguo, Li hongxu 2013, 34(3): 162-164.  Abstract ( 94 )   PDF (225KB) ( 186 )   The article presents a modeling program based on AutoCAD platform. The program can be used as an aiding tool for user to interpret the 3-view drawings. The program will separate the 3-view drawing into related three drawings according to the geometric relationship between each view, and will store every closed loop on each view. Based on the background knowledge base, the program can help the user to generate a model quickly. Related Articles | Metrics