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27 April 2012, Volume 33 Issue 2 Previous Issue    Next Issue

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A method for generating fabric pattern with Xinjiang ethnic style Zhao Haiying, Xu Zhengguang, Zhang Caiming 2012, 33(2): 1-8.  Abstract ( 65 )   PDF (1752KB) ( 268 )   Xinjiang ethnic fabric pattern with particular cultural connotation is an important part of Chinese national art treasures. To address how to use computer to generate fabric patterns with Xinjiang ethnic features and style is a challenging problem. A new extraction algorithm of pattern gene based on feature selection and primitive pattern filtration is proposed and the practicality of the method is testified. First, connected region is marked to carry out pattern segmentation for primitive pattern, pattern features are extracted to calculate features ratio and choose vote principle to filter primitive pattern for pattern genes. Then, Xinjiang ethnic fabric patterns are generated based on pattern genes and hexagonal structure. The experiments are carried out by extracting pattern genes in Uygur and Kazak fabric patterns based on the segmentation method and generating Xinjiang fabric patterns by geometric transformations of hexagonal tile,then the similarity of of design style is evaluated. The proposed method is able to quickly generate a large number of patterns with different national features. It can not only enrich design style sets, but also provide a new way to inherit ethnic heritage designs. Related Articles | Metrics

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Estimate algorithms and embedded crafts of curvature and torsion Fang Lijing, Lu Weijun, Huang Wenjun 2012, 33(2): 9-13.  Abstract ( 85 )   PDF (254KB) ( 356 )   Many applications of geometry processing and computer vision rely on geometric properties of curves, particularly their curvatures and torsions. This paper proposes some methods to estimate the curvature and the torsion, based on some algorithms for weighted least-squares fitting and local arc-length approximation in order to eliminate noises. By Maple procedure, statistical analysis of some selected common curves is carried out to get partial values of their curvatures and torsions, and then an approximate interval about ideal curvatures and ideal torsions is put forward. Furthermore, several test models for embedding specific ideal curvature or ideal torsion in crafts are taken into account. Related Articles | Metrics

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High-precision and adaptive quadrilateral mesh reconstruction Liu Li, Lü Xue, Bo Pengbo 2012, 33(2): 14-20.  Abstract ( 62 )   PDF (330KB) ( 183 )   A new algorithm to reconstruct quadrilateral meshes from large unorganized points with complex topology is proposed. The simplified points are connected with neighboring points according to given rules to form polygonal meshes, and then the polygonal meshes are subdivided to get higher precision and are changed into quadrilateral meshes. Finally, the vertices that have more degree are split. Experimental results demonstrate that the algorithm is fairly efficient for solving the problem of quadrilateral mesh reconstruction from complex data points. Related Articles | Metrics

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Research and realization of standard-part library oriented to the product lifecycle management Liu Yu, Yan Guangrong, Lei Yi 2012, 33(2): 21-25.  Abstract ( 112 )   PDF (352KB) ( 206 )   Design data is the source data of product lifecycle in manufacturing enterprise. Design data standardization largely determines the effect of the application of PLM systems. Accordingly, the study of materials information generation in the design process, materials information and transmission process in the PLM system, and how to build a single data source between design tools and PLM system are conducted. The construction and implementation of the standard library system oriented to the PLM are put forward. Collaborative application between the design tools and PLM system is achieved. The standard-parts library system based on the theory and the method has been developed in the SOLIDWORKS software platform and has been applied in the design department of a manufacturing enterprise. The effect of the application is obvious. Related Articles | Metrics

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The design and analysis of small H-vertical axis wind turbine blade Zhang Xuechen, Li Shan 2012, 33(2): 26-29.  Abstract ( 76 )   PDF (306KB) ( 468 )   Wind turbines (the windmill) is a conversion device that turn wind energy into mechanical energy, electrical energy or thermal energy. The vertical axis wind turbine has some advantages over the horizontal axis wind turbine. The small H-vertical axis wind turbine blades are analyzed. The load in different working environments are also analyzed. Stress calculation and checking methods are discussed. It can provide a reference for small H-vertical axis wind turbine blade design. Related Articles | Metrics

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Error controllable algebraic curve offset approximation based on cubic PH curve Shou Huahao, Jiang Yu, Miao Yongwei 2012, 33(2): 30-33.  Abstract ( 84 )   PDF (248KB) ( 217 )   A new algorithm that constructs offsets of a planar algebraic curve by approximating the algebraic curve with piecewise cubic PH curve is proposed. The approximation errors are also estimated. The approximate PH curve keeps some important geometric features of the original algebraic curve such as convexity, monotonicity and G1 continuity. Numerical experiments show that the algorithm provides an efficient approach to approximate parameterization of algebraic curves. The algorithm also provides a new method to calculate rational parameter representation of the algebraic curve offsets. Related Articles | Metrics

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Analysis and improvement of smallest enclosing disk algorithm on discrete set of points Li Hongjun, Zhang Xiaopeng 2012, 33(2): 34-38.  Abstract ( 97 )   PDF (272KB) ( 278 )   For calculating the smallest enclosing disk of a discrete set of points on the planar, three popular algorithms, i.e. the randomized incremental algorithm, the dual decision algorithm and the farthest point first progressive algorithm, are evaluated and an improvement of the randomized incremental algorithm is presented. The new algorithm employs the Axis-Aligned Bounding Boxes of the point set to optimize the initiate enclosing disk, which greatly improves the calculating efficiency. Numerical experiments show that the farthest point first progressive algorithm is the fastest one among the old three algorithms; the new algorithm is a fast and deterministic one, and can be helpful to the applications in computer graphics, facility locations, intelligent robot, and so on. Related Articles | Metrics

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Spiral-preserving geometric subdivision scheme for admissible G2 Hermite interpolation Deng Chongyang 2012, 33(2): 39-44.  Abstract ( 85 )   PDF (455KB) ( 197 )   To interpolate admissible G2 Hermite data, this paper proposes a modified geometric subdivision scheme with new subdivision rules near the end points of the curve. The method is based on the theory of planar biarc curve interpolation. Theoretical analysis shows that the limit curves of the modified subdivision scheme are planar spirals, which are curves of one-signed, monotone increasing or decreasing curvature. Numerical examples show that the modified subdivision scheme converge rapidly, and the limit curves are with nice shape. Related Articles | Metrics

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Triangular and quadrilateral surface construction using C-B spline Li Wei, Wu Zhuoqi, Ichiro Hagiwara 2012, 33(2): 45-48.  Abstract ( 83 )   PDF (259KB) ( 180 )   This paper provides a different solution to represent basic smooth elements like triangular and quadrilateral surface patches from mesh using C-B spline curves. C-B spline curves are developed by the basis {sin t, cos t, t, 1}, and it overcomes some shortcomings of the B-spline and non-uniform rational B-splines (NURBS) model, for example, they have to increase unnecessary control point in order to satisfy the data grid topology, their derivative and integral are complex and tedious, their degrees are too high, and it is difficult to discuss their continuous conditions. How to develop C-B spline curves into surface becomes an important problem. In this paper, the interpolation operators are constructed by using side-vertex method and a convex combination of these operators is achieved. The C-B spline curves are developed into triangular and quadrilateral surface patches which can be used in reverse engineering of CAD. Related Articles | Metrics

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Optimal parameterization of conic curves Li Yurong, Hu Fanggang 2012, 33(2): 49-52.  Abstract ( 60 )   PDF (165KB) ( 256 )   In the domain of CAGD and CG, optimal parameterization of specified segment on the algebraic curves is a hot question. Take the optimal approximation of arc-length parameterization as the criterion of optimal parameterization, and the optimal or close to optimal rational parameterization formula of any specified segment on the conic curves is obtained. The new method has strong self-adaptability. Finally, a experimental comparison of the results obtained by this method and by the traditional parametric algorithm is conducted. Related Articles | Metrics

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The application of a quasi-Legendre basis in the hyperbolic hybrid polynomial space Wang Yan, Tan Jieqing, Li Zhiming 2012, 33(2): 53-56.  Abstract ( 77 )   PDF (194KB) ( 196 )   In view of the wide usage of the orthogonal basis such as Legendre basis in the algebra polynomial space, the applications of the quasi-Legendre basis in inversion and offsetting approximations are given in this paper. Inversion approximation is constructed by using the blending of polynomial and hyperbolic functions, and the experimental results show that the approximation method is effective. An approach to approximate the offset curves of the H-Bézier curve based on the ideal approximation for the normal curve is presented. The algebraic approximation algorithms which can obtain the control points of the approximation curves directly are simple and more precise. Related Articles | Metrics

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A circle-restoring subdivision scheme for curve interpolation Han Jing, Han Xuli 2012, 33(2): 57-61.  Abstract ( 72 )   PDF (260KB) ( 182 )   A geometric 4-points interpolatory subdivision scheme with a parameter is proposed to overcome the deficiency of traditional 4-points interpolatory subdivision scheme that it can not generate non-polynomial curve, for example, circle. As three adjacent points confirm a circle, there are two arcs between every two adjacent points. The new generating point is determined by weighted average of two midpoints on the arcs. Interpolation formula and algorithm are described. This subdivision scheme can be convexity-preserving and restore a circle if all initial knots are on the same circle. Examples show the difference between this scheme and some traditional schemes. As the parameter becomes smaller, limit curve gets closer to initial controlling polygon. Related Articles | Metrics

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The application and promotion of the Newell formula Wang Ruimin, Wu Meng, Deng Jiansong 2012, 33(2): 62-67.  Abstract ( 107 )   PDF (257KB) ( 243 )   The application and promotion of the Newell formula in CAGD are discussed in this paper. This formula is used to calculate the area of a plane polygon and the normal vector of the plane the polygon lies on. Firstly, it is promoted to calculate the volume of a polyhedron. Secondly, the meaning of the Newell formula is discussed if the vertices are not on the same plane. Finally, some methods are proposed to simplify the calculation of the formula. Related Articles | Metrics

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A RANSAC-based ellipsoid extraction algorithm Cheng Zhiquan, Ye Yongkai, Li Bao 2012, 33(2): 68-71.  Abstract ( 108 )   PDF (266KB) ( 273 )   In this paper, an ellipsoid detection and extraction algorithm is proposed. The algorithm is designed and implemented based on the RANSAC (RANdom SAmpling Consensus) framework. Firstly, several minimum sets, one of which can define an ellipsoid, are selected from the point clouds by using random sampling strategy. Then, candidate set is formed from the effective ellipsoids, which come from the minimum sets and pass through the verification. Finally, the best approximate ellipsoids are extracted after the evaluation step using the score function. Experiments demonstrate that the algorithm is robust since it can effectively extract the ellipsoids from either manually synthesized point clouds or the raw data acquired by the scanners. Related Articles | Metrics

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An edge detection algorithm with multi-threshold selection and edge connection Zhu Xiaolin, Deng Xianglong, Hu Demin 2012, 33(2): 72-76.  Abstract ( 93 )   PDF (310KB) ( 301 )   For improving Kirsch operator, this paper presents an edge detection algorithm with multi-threshold selection and edge connection, which is used to detect the edge of images, especially medical images. The method first denoises the original image by Gaussian filter and calculates the gradient with the traditional Kirsch operator, then sets a lower threshold and adaptive thresholds to protect the weak edge and pick up the true edge, and finally detects the disconnected edge of the image by use of the modified edge connection algorithm. The experiment results show the efficiency of this method. Related Articles | Metrics

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Image denoising using mixed statistical model based on quaternion wavelet Yin Ming, Liu Wei 2012, 33(2): 77-82.  Abstract ( 78 )   PDF (596KB) ( 212 )   Image denoising and compression has been the classic image processing problem, and traditional methods are difficult to reach both requirements. Quaternion wavelet transform is the product of the combination of real wavelet, complex wavelet, quaternion theory and 2D-hilbert transform, and it is a new kind of multiresolution analysis of image processing tools. After quaternion wavelet transform, Image wavelet coefficients have certain intrascale and interscale correlation. This paper presents a mixed statistical model, which includes interscale bivariate non-Gaussian distribution and intrascale generalized Gaussian distribution. The minimum mean square error (MMSE) is used to estimate original image coefficients from wavelet coefficients with noise, so as to achieve the purpose of denoising. The experiment results show that this method can not only get signal-to-noise ratio enhancement and better visual quality, but also achieve high compression ratio. Related Articles | Metrics

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Video cutout method based on spatio-temporal similarity neighboring graph Zhang Hongchao, Zhang Lei, Huang Hua 2012, 33(2): 83-88.  Abstract ( 66 )   PDF (1879KB) ( 235 )   Video cutout is a fundamental yet frontier hot topic in video processing area, which plays an important role in video supervision, video editing, video composition and so on. Traditional methods mostly cut out the regions depending on the local similarity between the successive frames and the continuity of motion which are not able to accomplish a satisfying cutout results when the object regions are moving quickly or under occlusion. In this situation, lots of interaction may be needed. Based on the spatio-temporal similarity neighborhood, this paper presents a new model for efficient video cutout, which can be solved by max-flow/min-cut algorithm quickly. This method only needs very little interaction from the users, and more importantly, it is robust to the situations with foreground objects have fast motion or occlusion. Related Articles | Metrics

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A novel image encryption scheme with the capability of checking integrity based on inverse matrix Ou Duanhao, Sun Wei, Lin Bo 2012, 33(2): 89-92.  Abstract ( 63 )   PDF (339KB) ( 282 )   In this paper, a novel image encryption scheme with the capability of checking integrity based on inverse matrix is proposed for image security by utilizing combinatorial theory. A fragile and noised cipher-image is yielded by applying this scheme to grey-level image. Decryption is a simple reversed process of encryption. The integrity of cipher-image can be checked by human visual system without any complicated computations. When the cipher-image is tempered, we cannot gain any information about the secret image except a noised image. The key is simple and large enough. Theoretical analysis and experimental results demonstrate that the proposed scheme offers a high secure and effective mechanism for image encryption. Related Articles | Metrics

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Research on the on-machine verification simulation technology based on OpenGL Tang Wenjie, Wu Zhijun, Feng Pingfa, Bao Sheng 2012, 33(2): 93-97.  Abstract ( 69 )   PDF (378KB) ( 264 )   To achieve visual simulation of the computerized numerical control (CNC) on-machine Verification (OMV) system, this paper developed a simulation software of OMV system with OpenGL. The simulation system reads the STL model files to display the part, parse the XML measure-direct files which contain the coordinates of theoretical data to display the theoretical points, receive the data from the CNC system to achieve the real time simulation of the OMV system. Finally, the simulation system is verified with STL files from CATIA. Related Articles | Metrics

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Research on the Chinese phonetic 3D mouth animation based on weighted control algorithm Bi Yongxin, Han Huijian, Zhou Shiwen 2012, 33(2): 98-102.  Abstract ( 91 )   PDF (348KB) ( 372 )   Presently, the researches on the action of human’s mouth shape in the world are mainly carried out based on English words. However, such research based on Chinese words is not so much. Connected with our predecessors’ researches, this paper puts forwards a sound weighting control algorithm with the integration of the changing law of mouth shape and the time control of Chinese label when doing Chinese pronunciation. We use this algorithm to analyze the label in a sentence and a paragraph and compose a 3-dimensional model. This model can synchronize the continuously changing mouth shape with the sounds. A transition sequence of mouth shapes between two continuous mouth shapes is composed with the help of an interpolation method using cosine function. Thus, the action of human mouth synchronized with Chinese phonetics becomes more smooth and fluent. Related Articles | Metrics

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Research on representation for engineering drawings under feature-based modeling software environment Jiang Lijun 2012, 33(2): 103-107.  Abstract ( 106 )   PDF (454KB) ( 203 )   Connected with the series of national standards of Digital Product Definition Data Practices, the advantages and disadvantages of two-dimensional drawing expression method are expatiated. The basic form of three-dimensional drawing expression is analyzed under three-dimensional modeling software environment. This method takes full advantage of digital product definition data and enriches the teaching means of representation for three dimensional drawings. Related Articles | Metrics

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Study on the teaching system of engineering graphics based on creative configuration design Xiong Zhiyong, Luo Zhicheng, Chen Jinchang, Jiang Lijun, Deng Xuexiong, Liu Lin, Chen Chikun 2012, 33(2): 108-112.  Abstract ( 106 )   PDF (195KB) ( 325 )   As the important carrier of spatial imagination and creative thinking training, configuration design plays key roles in training students’ creative thinking abilities. Based on the research situation of engineering graphics education, a new curriculum system of engineering graphics based on creative configuration design is presented, which focuses on the configuration design and stands out the training of students’ creative thinking ability. Then, the new curriculum system is deeply explained from three aspects: the educational reform target, the educational reform content and the teaching practice. The teaching practices indicate that the curriculum system can train student's creative thinking ability in configuration design very well. Related Articles | Metrics

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Behavior analysis and counting based class surveillance video Ou Wennuan, Tian Xuhong, Zhu Tonglin 2012, 33(2): 113-118.  Abstract ( 106 )   PDF (403KB) ( 310 )   Based on the static single-camera surveillance video, this paper proposes a video analysis based on statistical methods of classroom behavior. Firstly, video sequences are segmentalized and moving targets are tracked. Then, by tracking the location of the target and monitor status information for the regional model, four different displacement models are presented. Finally, the displacement model is used to achieve the number of behavior in or out of the control area. This method is simple and practical, can not only achieve satisfactory results, but also have certain robustness. The experimental result shows some practical significance for schoolrelated departments to understand and grasp the classroom teaching circumstances. Related Articles | Metrics