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《计算机辅助设计与图形学学报》2014,(1)
为解决过渡特征对基于图匹配的三维CAD模型检索算法的效果和效率影响问题,提出一种三维CAD模型检索中过渡特征的识别及过滤算法.首先利用基于规则判断的方法识别出B-Rep模型中存在的过渡特征;然后根据识别结果对CAD模型的属性邻接图进行重构,以消除因过渡特征的存在对模型几何及拓扑信息造成的影响;最后利用重构的属性邻接图、通过子图同构方法实现基于过渡特征过滤的三维CAD模型检索.实验结果表明,该算法能够有效地实现对多种过渡特征类型的过滤,检索结果更符合实际工程需求. 相似文献
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现有基于边信息的半监督维数约减算法大都是直接将保留边信息和数据拓扑结构的目标函数相加,因此数据拓扑结构中的错误连接不会因已知的边信息而得到修正.提出通过边信息传播及修正机制将边信息融入到数据拓扑结构图中的方法,从而在保留边信息的同时保留更为真实的数据拓扑结构信息.实验结果表明本文所提出的算法较之其它算法,对数据降维后用于分类时可取得较高的准确率,且算法对创建的KNN图中的参数K最具鲁棒性. 相似文献
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针对雷达组网量测数据不确定性大、信息不完备等特点, 基于决策树分类算法的思想, 创建类决策树的概念, 提出一种基于类决策树分类的特征层融合识别算法. 所给出的算法无需训练样本, 采用边构造边分类的方式, 选取信 息增益最大的属性作为分类属性对量测数据进行分类, 实现了对目标的识别. 该算法能够处理含有空缺值的量测数据, 充分利用量测数据的特征信息. 仿真实验结果表明, 类决策树分类算法是一种简单有效的特征层融合识别算法.
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本文在基于扫描线的多边形填充算法基础上,通过建立活性边表、Y桶链表,以简化扫描线与边相交的判断,保留了基于扫描线填充适用于任意多边形的优点。 相似文献
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基于编码与分类技术的任意多边形裁剪新算法 总被引:3,自引:0,他引:3
首次将编码与分类技术引入任意多边形的矩形窗口裁剪,通过编码分类技术根据多边形边与裁剪窗口的相对位置将边分为六类。采用一次编码技术获取一类窗内边,舍弃二类窗外边,得到必须求交的三类边;采用二次编码技术舍弃四类窗外边,得到需要求交的五、六类边;进一步提出裁剪窗口顶点相对于多边形的分类,利用窗口顶点分类和多边形边的编码特征快速处理三类、五类、六类窗口相交边。通过编码分类技术减少了多边形裁剪的运算量,并有效地维护了多边形的拓扑关系。实验结果表明算法稳定可靠,可实现对任意凹凸多边形的裁剪,在多边形与窗口的各种相对位置均具有较高的运算效率。 相似文献
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工程图纸扫描图象的线段完整识别算法 总被引:1,自引:0,他引:1
给出一种基于单义域邻接图的完整识别线段算法。采用单义域邻接图来描述工程图纸扫描图象的几何属性与拓扑关系。通过分析单义域几何与拓扑特征定交点域。首先选取线段域作种子线段,以交点域为连接线索,选取共线且误差最小的线段域进行种子线段生长。从而实现线段完整识别,该算法有铲地解决了在线段与线段相交及线段与圆弧(圆)相交和相切情况下如何保证图元描述完整性问题,大大提高了整体矢量化水平。 相似文献
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改进的圆角特征识别与抑制方法 总被引:1,自引:0,他引:1
提出了一种利用圆角面截面线曲率特性识别圆角特征的改进方法.该方法首先识别出圆角面和点过渡面,然后将相邻圆角面和点过渡面组成圆角特征,并对圆角特征中包含的所有面进行整体抑制.通过曲面延伸求交计算圆角特征抑制后新模型的点、边几何信息,并调整相应的拓扑关系重构新模型.该方法扩展了现有方法的适用范围,支持含有自由曲面的实体模型中的等半径、变半径圆角特征的识别和抑制.实验结果表明所提出的方法有效可行. 相似文献
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从高质量曲面网格生成的需求出发,提出了一种基于T-Spline的全自动几何拓扑修复方法.本文方法创新性主要可归纳为:1)对原有计算机辅助设计(Computer aided design,CAD)几何模型不进行任何修改保留其本真,自动识别CAD几何模型中常见不必要的几何特征,成功解决了CAD几何模型中存在的几何瑕疵,如短边、窄面、退化边、退化面、非连续光滑边界及尖锐特征等,利用新生成的"虚边"、"虚面"处理几何瑕疵,同时通过虚拓扑重构CAD几何模型的B-Rep;2)开发了一套CAD/CAE集成系统,统一了几何模型与计算分析模型,实现计算机辅助工程(Computer aided engineering,CAE)与CAD两者的无缝集成,所有拓扑修复操作及后续CAE分析计算均在同一环境下进行,避免了几何模型在CAE与CAD系统间进行转换时造成的数据丢失.该方法能够对复杂实体实现全自动几何拓扑修复及网格生成,实验表明,在保证不失真的前提下,修复后的几何模型能够生成质量良好的网格且能降低网格的生成规模,验证了本文方法的实用性和有效性,以满足工程实际分析的需要. 相似文献
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Incremental reconstruction of sharp edges on mesh surfaces 总被引:2,自引:0,他引:2
Charlie C.L. Wang Author Vitae 《Computer aided design》2006,38(6):689-702
Limited by the regular grids in computing, many modelling approaches (e.g. field-based methods) sample 3D shape insensitive to sharp features therefore exhibit aliasing errors, by which a lot of sharp edges and corners are lost on the reconstructed surface. An incremental approach for recovering sharp edges on an insensitive sampled triangular mesh is presented in this paper, so that shape approximation errors are greatly reduced. Either chamfered or blended sharp edges on an input triangular mesh could be successfully reconstructed by the signals inherent in the mesh. As a non-iterative method, our approach could be finished in a very short time comparing to those diffusion-based sharp-feature reproducers. The region embedding sharp features is first identified through normal variations. The positions of vertices in the sharp-feature embedded region are then predicted progressively from outer to the inner of sharp regions so that sharp edges could be recovered in the sense of region shrinking. 相似文献
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We introduce the point-and-edge model for edge-preserving modeling and rendering. Besides a set of surface points, the point-and-edge
model also includes edge points representing the sharp edges in the model. The surface points and the sharp edges are relatively
independent of each other. We present a feedback algorithm to simplify the point-and-edge model with bounded error based on
an edge-preserving clustering method. An efficient constrained splatting method is used to preserve the sharp edges in the
rendering, regardless of the surface point density. 相似文献
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This paper presents a simple and general modeling primitive, called a block, based on a generalized cuboid shape. Blocks are laid out and connected together to constitute the base shape of complex objects, from which is extracted a control mesh that can contain both smooth and sharp edges. The volumetric nature of the blocks allows for easy topology specification, as well as CSG operations between blocks. The surface parameterization inherited from the block faces provides support for texturing and displacement functions to apply surface details. A?variety of examples illustrate the generality of our blocks in both interactive and procedural modeling contexts. 相似文献
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为了研究聚合物共混体中分散相的形态和分布对共混物阻隔性能的影响,本文建立了分子扩散通过聚合物共混体系一般化的数学模型,并由蒙特卡罗方法模拟共混分散体系的分布,经计算机模拟计算后,得到片状的分散相具有较好的阻隔效果,该结论与实验结果相符。 相似文献
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Kenshi Takayama 《Computer Graphics Forum》2019,38(2):37-48
The combinatorial dual of a hex mesh induces a collection of mutually intersecting surfaces (dual sheets). Inspired by Campen et al.'s work on quad meshing [CBK12, CK14], we propose to directly generate such dual sheets so that, as long as the volume is properly partitioned by the dual sheets, we are guaranteed to arrive at a valid all‐hex mesh topology. Since automatically generating dual sheets seems much harder than the 2D counterpart, we chose to leave the task to the user; our system is equipped with a few simple 3D modeling tools for interactively designing dual sheets. Dual sheets are represented as implicit surfaces in our approach, greatly simplifying many of the computational steps such as finding intersections and analyzing topology. We also propose a simple algorithm for primalizing the dual graph where each dual cell, often enclosing singular edges, gets mapped onto a reference polyhedron via harmonic parameterization. Preservation of sharp features is simply achieved by modifying the boundary conditions. We demonstrate the feasibility of our approach through various modeling examples. 相似文献
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基于深度学习的图像去噪方法在使用空洞卷积神经网络时,去噪后的图像容易在尖锐边缘生成伪像,并且为了处理不同的噪声水平,需要训练多个特定的去噪模型.对此文中提出基于空洞卷积神经网络的噪声水平可调的高斯去噪方法.加入噪声水平图,实现噪声水平可调性,并使用改善的空洞卷积及可逆的下采样技术,缓解由于传统空洞卷积带来的图像尖锐边缘的伪成像问题.将下采样的子图与相应的噪声水平图都输入到非线性映射模型中,并使用改善后的减小空洞率的神经网络进行训练.实验表明,文中方法在获得GPU加速的同时具有调节噪声水平的能力,能够改善尖锐边缘的伪像问题,保留更多图像细节 相似文献
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The paper presents a new adaptive full reference method for quality measurement of image enhancement algorithms. The method is based on the analysis of basic edges??sharp edges which are distant from another edges. The proposed basic edges metrics calculates error values in two areas related to typical artifacts of image enhancement algorithms: basic edges area and basic edges neighborhood. The metrics are illustrated with an application to image resampling and image deblurring but it is also applicable for image deringing and image denoising. 相似文献