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30 August 2014, Volume 35 Issue 4 Previous Issue    Next Issue

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Data-driven Synthesization for Large-scale Water Animation Wang Chengbo, Zhu Dengming 2014, 35(4): 491-497.  Abstract ( 93 )   PDF (4582KB) ( 209 )   A new framework is presented for synthesizing water animation with large size and rich details. The main idea of our framework consists of two steps: reconstructing mesh model from videos and spanning the mesh by quilting. First we simplify the shape from shading method which is linearly approximated, and use it to reconstruct the outdoor water with large scale which satisfies the Lambert surface assumption. The result is optimized with several smooth methods according to the constraint of consistency in time and space. Then a quilting method is introduced for triangle mesh, in which we sample smaller blocks from the constructing mesh based on the principle of distance minimization and merge the blocks to get the seamless surface. The process is completed with four kinds of water. Results demonstrate that the synthesized water animation has high sense of reality and balance the scale with detail very well. This method can conveniently synthesize large-scale water animation meeting use′s demand. Related Articles | Metrics

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A New Method for Determining the Intersection, Union and Difference of Two Polygons with Holes Zhao Jun, Hao Yongxing 2014, 35(4): 498-503.  Abstract ( 84 )   PDF (352KB) ( 274 )   A new algorithm is presented for Boolean operation of two polygons with holes based on minimum circle. Firstly, outer rings of Polygon P and Q are initialized to counter-clockwise direction, and inner rings are initialized to clockwise direction. "Bridge edges" connect the outer and inner rings, so the polygon with multiple rings is converted to single ring. Then the edges connecting to each intersection point of P and Q are arranged in sequential order. Next, all minimum circles are found by the minimum turning angle rule. These minimum circles are classified according to edges direction in P and Q. Intersection, union, and difference of the two polygons correspond to different kinds of minimum circles. The algorithm has explicit geometric significance, and well resolves the problems in special cases. Related Articles | Metrics

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Implicit Fitting Using RBF Based on Ellipsoid Constraint Han Xie, Wu Jingmin, Han Huiyan, Li Dingzhu, Sun Fusheng 2014, 35(4): 504-510.  Abstract ( 96 )   PDF (1541KB) ( 222 )   Implicit surface fitting to a set of scattered points plays an important role in solving many problems occurring in virtual reality and so on. This paper presents an implicit surface fitting algorithm using radial basis functions with an ellipsoid constraint. This method can fit the data accurately by use of information of point clouds. The fitted shape can still capture the main features of the object when the data sets are sparse. The fitted surface may contain many redundant components and not represent the actual shape properly with longer time when fitting large data set. Large-scale scattered data is needed to be subdivided adaptively, these subdivided data fit simultaneously and these simpler implicit surfaces blended smoothly. The experimental results show that the algorithm is good in preserving feature and can improve the efficiency obviously. Related Articles | Metrics

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Extension of Bézier Curves Based on the Design of Matrix Using Binomial Coefficient Guo Dayong, Cheng Jiayi 2014, 35(4): 511-517.  Abstract ( 97 )   PDF (1234KB) ( 190 )   Based on the binomial coefficient, a matrix with shape parameters is designed. And then it is used for constructing a new type of basis function called A-Bernstein basis function. It has the same degree with the Bernstein basis function and shares several same properties. According to the A-Bernstein basis function, a corresponding curve named A-Bézier curve is derived. It not only shares the same properties with a Bézier curve, but also can be adjusted in shape by modifying the shape parameter without the changing of original control points. Furthermore, the modification of the matrix is illustrated. It can be used for modifying the A-Bézier curve. Examples show this method is intuitive and effective. Related Articles | Metrics

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Optimal Parameterization Based on the Variation of the Parameter Speed Chen Jun, Zhou Lian 2014, 35(4): 518-522.  Abstract ( 77 )   PDF (499KB) ( 200 )   Based on the improved criteria for parameterization, a new optimal parameterization with the help of the piecewise linear transformation is obtained. By taking the nodes as the free variables and the variation of the parameter speed as the objective function, the simple analytical solution of a system of equations is presented. The new expressions of the original curve are a series of Bézier curves, which are different from the expression by the Möbius transformation. The new optimal parameterization is close to the arc-length parameterization, which is displayed by the numerical example. Related Articles | Metrics

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Constructing Bicubic Bézier Surface from a Given Spatial Cubic Bézier Geodesic Curve 2014, 35(4): 523-527.  Abstract ( 94 )   PDF (286KB) ( 185 )   Geodesic curve on a surface is a kind of important one and has its applications in computer vision and image processing, such as in garment design. A curve is a geodesic if and only if its rectifying plane coincides with the tangent plane to the surfaces. This fact is used to construct bicubic Bézier pathes through geodesics, and the continuity of composite Bézier patches through pairs of geodesics discussed. Finally, some examples are provided to demonstrate the effectiveness of the proposed method. Related Articles | Metrics

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A New Kind of Curves and Surfaces Yan Lanlan, Han Xuli 2014, 35(4): 528-535.  Abstract ( 118 )   PDF (470KB) ( 206 )   Some groups of blending functions consisting of n (n≥3) functions are given. They have non-negativity, normalization, symmetry and special endpoint property. The curves defined by them possess convex hull property, geometric invariance, symmetry. The starting and ending points of the curves are the midpoints of the first and last edges of their control polygons. At the starting points of the curves, both the first order and the second order derivative vectors are parallel to the first edge of the control polygon. And at the ending points, the first order and the second order derivative vectors are parallel to the last edge of the control polygon. Given m (m > 3) control points, we define one curve segment, and a composite curve consists of several segments. Each segment can be determined by different number of control points. So the same control points can be used to define a variety of shapes. The composite curve is G2 continuous at the piecewise points. The tensor product surfaces defined by the function groups also have many good properties similar to the curves. Related Articles | Metrics

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Hierarchical Segmentation Algorithm of Rapid Prototyping Based on Parts Assembly Wang Chunxiang, Hao Zhibo 2014, 35(4): 536-540.  Abstract ( 63 )   PDF (815KB) ( 245 )   In order to improve the efficiency of stratification based on the required accuracy, the thought of uniform thickness layering is put forward on different assembly functions of STL model of assembly requirement. The new algorithm divides the model into different parts along the molding direction, and equally layers the parts based on different thicknesses. The sort of streamline method is used to the uniform thickness layering algorithm of each section. The triangles which intersect with stratification plane are directly extracted through the three sorting of the model, and then stratification plane contour is output after quick intersection. The new algorithm is realized by MATLAB software. A tooth with closed cavity is used as an example for verifying it. The results show that the new algorithm has high flexibility, the required accuracy of component in function and assembly is satisfied, and the section contours are quickly output. Related Articles | Metrics

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Parametric Modeling System for Stator Windings of Turbo Generator Zhang Qinglei, Qian Guangpu 2014, 35(4): 541-547.  Abstract ( 122 )   PDF (1606KB) ( 219 )   A new modeling method of turbo generator stator end windings is proposed, which is advanced from spreading plane to stereoscopic, to realize parametric modeling of stator windings. Mathematical model of parametric modeling is established and key 3D-modeling steps are given. Then through using secondary development technique, programming technique and database technique, an automatic parametric modeling system of the stator end windings of turbo generator based on UG/NX platform is developed. Taking a million-kilowatts-class turbo generator as example, the validity and feasibility of this method and system are testified. Related Articles | Metrics

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Application of GPS Technology Work to Model Definition Wu Canhui, Xia Xiaoli, Liang Yong, Cai Jinhui, Wang Ning 2014, 35(4): 548-552.  Abstract ( 64 )   PDF (1046KB) ( 252 )   Aiming at the problem of model based definition (MBD) in the assessment of coherence between product geometry definition and measurement, GPS (geometrical product specification and verification) is proposed to be applied to model definition. The solution scheme is established based on the duality principle of GPS, and key technologies of GPS used in model definition are analyzed. GPS used in MBD is illustrated through face-gear model definition examples. Combined with the example of the face-gear tooth surface accuracy assessment, the impact of product assessment is expatiated. Thus, an idea is provided for the combinative application of MBD and GPS. Related Articles | Metrics

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Computer Aided Ergonomics System Based on Multi-constraints for Deep Submergence Vehicle Li Bo, Ji Xiaomin, Chen Dengkai, Yu Suihuai 2014, 35(4): 553-562.  Abstract ( 88 )   PDF (1827KB) ( 162 )   In order to improve design efficiency of intelligent generation and optimization about design scheme, and increase the designer′s understanding of physiological, psychological and environmental constraints about DSV ergonomics design, the layout design about man machine interface component is solved by genetic algorithm, knowledge reasoning is used to the color ergonomic design about manned capsule, and the intelligent optimization about manned capsule ergonomics design based on particle swarm optimization algorithm. The prototype system is developed for manned capsule CAED based on UG. The feasibility of layout design solution about man machine interface component and intelligent optimization about manned capsule ergonomics design is verified by using a design example. Related Articles | Metrics

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Image Edge Detection Based on Wavelet and Singular Value Decomposition Zhu Xiaolin, Li Xueyan, Xing Yan, Chen Man, Zhu Yuanzhu 2014, 35(4): 563-570.  Abstract ( 117 )   PDF (1108KB) ( 221 )   Traditional image edge detection algorithms do not perform well in noise suppression. For solving the problem, this paper presents a new method based on wavelet and local gradient field singular value decomposition to detect image edge. First, the wavelet transform (WT) is applied to the image in order to utilize the time-frequency localization characteristic of WT to extract the accurate edge character. Then the local gradient field singular value decomposition (SVD) is used to the gradient field calculated by the wavelet. The feature and good stability of the singular values (SVs) enhance edge character and suppress noise. The experimental results of edge detection illustrate that the proposed method can not only extract clear and complete single-pixel edge in the images without noise, but also find ideal edge from noised images. Related Articles | Metrics

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Image Enhancement Algorithm Combining with Threshold De-noising and Edge Optimization Ye Shitong 2014, 35(4): 571-576.  Abstract ( 147 )   PDF (1038KB) ( 214 )   Image is prone to interference problems in the transmission process. By studying the image enhancement technology and comparative analysis, an image enhancement algorithm is proposed combining with the threshold de-noising and edge optimization. The algorithm is based on the Wavelet Contourlet transform and the inherent characteristics of the human visual. The decomposed image coefficients are classified. The edge area signal is optimized by using the improved edges of the gain factor optimization algorithm. The non-edge of the area is de-noised by improved soft threshold de-noising algorithm. The experiments show the algorithm has the characteristics of high accuracy and de-noising ability, and it can effectively protect edge signal while de-noising. The experimental results are consistent with the expected target. Related Articles | Metrics

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Moving Object Detection Based on Random Image Selection and Adaptive Background Updating Li Xinxian, Yu Ye 2014, 35(4): 577-584.  Abstract ( 75 )   PDF (1886KB) ( 295 )   In order to overcome the phenomena of illumination changes, occlusion and fake target, which appear easily in the moving target detection process, a random image selection and adaptive background updating method for moving object detection is proposed in this paper. First, the background is initialized through selecting an image from the video sequence randomly, and then it is updated adaptively and iteratively based on change marker matrix to extract reliable background images. The experiment results demonstrate that the background extracted through this algorithm does not have the mixing phenomenon, so a reliable background can be constructed, and the target object can be detected clearly even in the case of large changes in illumination and occlusion between moving objects. Related Articles | Metrics

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License Plate Recognition in Complex Background Base on#br# HSV Space and Template Matching Xie Yongxiang, Dong Lanfang 2014, 35(4): 585-589.  Abstract ( 80 )   PDF (424KB) ( 329 )   As an important means of the automatic traffic management, the technology of license plate recognition plays a very important role in transportation surveillance and control. License plate recognition can generally be divided into four parts: vehicle license plate location, license plate correction, license plate character segmentation and character recognition. In license plate location, it is often applied to simple background scene, but not suitable for complex background if only using the texture or color features of the location. In character segmentation, the method of single line is mature, but the method of double line license is not ideal. A location method is provided that combine twice color calibration in HSV space and texture feature and a segmentation method of single or double rows of characters. Because of the property of fixed colors in a plate, the picture is marked twice, and then the projection method is used to locate the plates. The experimental result reaches 98% accuracy in the test of 200 different background pictures. Meanwhile, the improved method of template matching reaches 95% accuracy. Related Articles | Metrics

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Machine Vision Inspection of Surface Defect for Arc Magnet Du Liuqing, Yu Yongwei 2014, 35(4): 590-594.  Abstract ( 147 )   PDF (423KB) ( 324 )   Aiming at the importance of defect inspection and the shortcoming of manual inspection in production process, the automatic machine vision detection and classification method is studied for the surface defect of arc magnet. Firstly, against many kinds of defects with low contrast, textured background and uneven brightness, the scan line gradient is defined to constitute feature vector with the standard deviation of the scan line grayscale. Secondly, the image segmentation method based on two-class support vector machine is presented to identify and extract defects. Finally the improved method on multi-class support vector machine is proposed to classify these extracted defects, which solved the problems of unclassifiable region and improved classification accuracy and effectiveness. The experimental results indicate that all kinds of defects of the different sub-region can be detected rapidly and accurately. The detection rate of defects can reach 96% and the classification rate of defects is higher than 91%. Related Articles | Metrics

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Fitting B-spline Curves to Gas Explosion Data Points with Multi-constraints Yang Zhengyuan, Shen Liyong 2014, 35(4): 595-602.  Abstract ( 78 )   PDF (1893KB) ( 181 )   Fitting data points by spline curves is an important method of data processing. A typical example of fitting with multi-constraints in project is presented. Gas explosion analysis is an important issue related to production safety. Precise and safe explosive boundaries are helpful to hazard prediction and control. This paper analyzes the experimental data obtained from the firefighting company, and provides the explosion bounds and explosive strength based on multi-constrained spline fitting method. Specifically, different characteristics of the gas explosion are converted to mathematical constraints and then are simplified appropriately. Fitting B-spline curves to the data points under these conditions results in the explosive strength curves with the explosive characteristics. This method can be generalized to multi-factor explosion analysis, not restricted to dimensions. Related Articles | Metrics

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Effect Analysis in the Teaching Efficiency of Engineering Drawing and Mapping Yang Li, Hao Yuxin, Lv Mei 2014, 35(4): 603-605.  Abstract ( 86 )   PDF (227KB) ( 215 )   This paper provides the reports of effect on the teaching reform of engineering drawing with the mapping in the experimental classes and regular classes for two years through the three aspects of the questionnaire survey, surface quality and assessment methods. The results show that the teaching reform has achieved the desired and obvious effects, especially in the cultivation of students' learning initiative, learning ability, knowledge comprehension and application ability etc. Related Articles | Metrics

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Teaching Analysis Method of Dimensioning for Overlapped Combination Solid Yi Shengyao, Shang Jianzhong, Xu Haijun 2014, 35(4): 607-612.  Abstract ( 103 )   PDF (546KB) ( 198 )   Dimensioning of combination solid is difficult in engineering drawing teaching, so it has a very important significance to explore an effective teaching analysis method. It requires students to dimension combination solid accurately, perfectly and clearly, but the current teaching method cannot guide them how to do it. A new teaching analysis method is presented in this paper about how to dimension the overlapped combination solid. Finally, three principles of dimensioning of overlapped combination solid are raised by the analysis of classifying overlapped combination solid and expanding the definition of dimension. Three principles presented in the paper are very useful and they can guide students to choose the size dimension and location dimension of basic geometric body correctly while using analytical method of shape to dimension overlapped combination solid. So a correct, complete dimensioning effect can be achieved. Related Articles | Metrics

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Study and Implement of Assignment Auto-checking System for Civil Engineering Graphics Yang Wanli, Wang Ning, Wang Guangjun 2014, 35(4): 613-618.  Abstract ( 95 )   PDF (485KB) ( 224 )   It is a difficult task for university teachers to check assignments of civil engineering drawing manually. In order to develop an assignment auto-checking system to improve efficiency, the recognition of vector graphics and implementation scheme of the assignment auto-checking system are discussed based on self-made vector graphics platform ATVGP. A new method of curve recognition is proposed in our study. Auto-checking system for civil engineering drawing assignments is achieved by using of VC++ programming environment. Related Articles | Metrics

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Reform and Practice in the Teaching of Subject "Mechanical CAD" Based on the Principle of from Person to Person Duan Luqian, An Xueguo 2014, 35(4): 619-622.  Abstract ( 73 )   PDF (206KB) ( 200 )   With sustained expansion of foreign exchanges with abroad in recent years, the amount of foreign military students studying in Chinese military academies is increasing and the demand for training is also getting higher. The varieties in educational level and background of the foreign military students, however, become more obvious and severe. To solve the contradiction between the higher demand for training quality and the ever increasing individual varieties, the teaching idea of different person with different means is put forward in this article and put into practice in the subject of "Mechanical CAD", and a satisfactory result has been obtained from the teaching practice. Related Articles | Metrics

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Study of Massive Data Curve Plotting Method in Aerospace Test System Ma Zhigang, Liu Wenyi 2014, 35(4): 623-629.  Abstract ( 65 )   PDF (326KB) ( 357 )   In aerospace test field, the representation of test data in curve format is always indispensable, which can reflect the change or conditions in test system. In view of the massive data processing in curve plotting, reading method is adopted, which can satisfy with the processing of the massive data over 4GB. When the amount of data is large, the general curve plotting methods may bring about the low implementation efficiency or the flicker problem in the display area. The plotting program is optimized by the API function "Polyline" in MFC, and the program′s execution efficiency is improved greatly. The double-buffering method is applied to clear the flicker in the plotting area when the curve is displayed, and the plotting time is further shortened. Related Articles | Metrics

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Exploration on Bilingual Teaching of Engineering Graphics Under "2 +2" Mode Luan Yingyan, Gong Na 2014, 35(4): 630-632.  Abstract ( 81 )   PDF (347KB) ( 234 )   Bilingual teaching for these students is necessary in the "2 +2" Sino-foreign joint training mode. This paper analyzes the basic status of bilingual teaching, the teaching objectives and the teaching difficulties. Engineering Graphics Course is adjusted and reformed to achieve the requirements of the joint training mode. Related Articles | Metrics

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A Design Method for Engineering Graphics Courseware Based on AutoCAD and PowerPoint Lv Mei, Yang Li, Hao Yuxin 2014, 35(4): 633-636.  Abstract ( 80 )   PDF (497KB) ( 244 )   The present situation of engineering graphics is less class hours, more students, and the same teaching content. Some functions and characteristics should be provided by engineering graphics courseware based on the current situation of engineering graphics. In the process of courseware development, we have a comprehensive application of AutoCAD and PowerPoint. The engineering graphics courseware introduced in the article can satisfy with the requirements of the current situation. The courseware can show the students the drawing process and methods step by step. An example illustrates the process of making courseware. This method is simple to use, but it needs to spend more time. However, once the courseware is finished, we can get more convenience. Related Articles | Metrics

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An Improved Image Edge Detection Algorithm Based on Roberts and Grey Relational Analysis Wen Yongge, He Hongzhou, Li Haiyang 2014, 35(4): 637-642.  Abstract ( 103 )   PDF (494KB) ( 235 )   Aiming at the problems of Roberts operator being easy to miss detection pixels and sensitive to noise, an improved edge detection algorithm GRA-Roberts is proposed. By improving the Roberts operator, the precision and the anti-noise performance is enhanced. Combined with the grey relational analysis, referring to the improved Roberts operator, the image edge is detected based on the grey relational grade. The experiment results show that GRA-Roberts can not only get over the above drawbacks of the Roberts operator algorithm effectively, but also get better detection effects compared to other related grey relational algorithms. Related Articles | Metrics

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Image Denoising Based on Cloud Model Code Li Dan, Wang Hongtao 2014, 35(4): 643-647.  Abstract ( 103 )   PDF (2674KB) ( 197 )   The presented cloud model algorithm is used to improve the quality of denoised image. Firstly, the normal cloud generator is used to produce cloud droplet. Secondly, the positive cloud droplet is mapped to the pixels that grayscale is bigger than the average grayscale of image, the negative cloud droplet is mapped to the pixels that grayscale is smaller than the average grayscale of image, and different code is represented by gray feature of different pixel. Thirdly, the rule of code is divided into flat and non flat blocks, and the flat block area is maintained quality level. Finally, the processing of image mosaic is described. The experiment results show that this mechanism is efficient and can find the global optimal solution with high probability. Related Articles | Metrics

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Progressing of Augmented Reality to Assistance Maintenances Technology Zhao Shouwei, Ma Dongxi, Zhang Yong, Ma Sasa, Yu Ming 2014, 35(4): 648-654.  Abstract ( 283 )   PDF (2021KB) ( 630 )   Augmented reality (AR) in the application of complex equipment maintenance can increase the information content of maintenance support and the comprehensive capability of maintenance operation, which improves maintenance support efficiency. Based on the analysis on the typical state-of-the-art AR prototype system, the feasibility of AR using the complex equipment maintenance is explored. Meanwhile, the solving method is provided aiming to the critical technology in term of the AR realization. Furthermore, the previews are forward to the trend of development of AR. Related Articles | Metrics