Surface feature based mesh segmentation

Mesh segmentation has a variety of applications in product design, reverse engineering, and rapid prototyping fields. This paper presents a novel algorithm of mesh segmentation from original scanning data points, which essentially consists of three steps. Normal based initial decomposing is first performed to recognize plane features. Then we implement further segmentation based on curvature criteria and Gauss mapping, followed by the detection of quadric surface features. The segmentation refinement is finally achieved using B-spline surface fitting technology. The experimental results on many 3D models have demonstrated the effectiveness and robustness of the proposed segmentation method.     

一种基于特征线的曲面网格分割方法

各类网格分割法将曲面网格进行分割后,各子网格区域之间的交界线便可以作为曲面网格的封闭特征线。相反,如果根据网格模型的几何、拓扑特征,确定了网格模型的封闭特征线后,网格曲面便被这些特征线分割开来。为此,从曲面网格封闭特征线的角度出发,提出一种基于特征线的曲面网格分割方法。实验验证了该方法的可行性和有效性。     

多机并发系统中通信模型分层抽象的方法

针对多机并发系统的复杂性,为了辅助用户能从多个角度和层次全面地理解并发系统,就需要逆向产生出能够反映软件系统框架结构的高层架构。基于此本文以进程为边界,提出了一种分层抽取多机并发系统通信模型的方法。此方法基于反射和开放编译的植入机制来获取所需要的动态信息,在此基础上运用分层抽象的策略,分别从系统、节点、进程三个层次对多机并发系统的通信结构和设计结构进行逆向恢复,最后对该方法进行系统的实验研究。结果表明,分层抽象所得到并发系统的通信模型能够正确、有效地反映系统设计时的高层架构关系。     

Hierarchical part-type segmentation using voxel-based curve skeletons

We present an effective framework for segmenting 3D shapes into meaningful components using the curve skeleton. Our algorithm identifies a number of critical points on the efficiently computed curve skeleton, either fully automatically as the junctions of the curve skeleton, or based on user input. We use these points to construct a partitioning of the object surface using geodesics. Because the segmentation is based on the curve skeleton, it intrinsically reflects the shape symmetry and articulation, and can handle shapes with tunnels. We describe a voxel-based implementation of our method which is robust and noise resistant, able to handle shapes of complex articulation and topology, produces smooth segment borders, and delivers hierarchical level-of-detail segmentations. We demonstrate the framework on various real-world 3D shapes. Additionally, we discuss the use of both curve and surface skeletons to produce part-type and patch-type, respectively, segmentations of 3D shapes.     

Part-based localisation and segmentation of landmark-related auditory cortical regions

We recently presented a method for the delineation of cortical regions of interest that relies on the finite element decomposition of shape [21]. Our current work strengthens and extends the proposed technique with the following contributions: First, we provide a detailed discussion of the computational challenges related to applying the hierarchical shape modelling and energy minimisation approach to the representation and segmentation of specific areas in cortical surfaces. Second, we analyse the underlying heuristics in order to elucidate the representational power and accuracy of the a priori constrained, partial model of the auditory cortex anatomy, and improve the cortical landmark localisation. We show experimentally that a valid parametric prior can be built from expert prior knowledge in a straightforward manner. By employing the advantages of the hierarchical shape decomposition, the model can be substantially improved on the basis of training sets, which are much smaller compared with state-of-the-art methods.     

Decomposing the problem of constrained surface fitting in reverse engineering

This paper presents a practical solution for surface fitting problems with prioritized geometry constraints in reverse engineering. The approach allows prioritizing constraints and uses them for decomposing the problem into a set of sequentially solved, manageable sub-problems. The result of each solution step is trade-off between satisfying the set of constraints and fitting of the surfaces to the measured points. The overall solution process trades off solution quality with complexity of the problem. Solution quality is checked against pre-defined tolerances assigned to the geometry constraints. Results on a benchmark problem demonstrate the suitability of the approach to solving large problems with hundreds of surfaces and constraints.     

基于三角网格的交互式数据分割研究

为了有效地提高三角网格模型数据分割的效率和准确性,设计了一种交互式的数据分割算法--基于夹角追踪的区域边界生成方法.该方法在自动提取三角网格模型特征点的基础上,交互地选取区域边界的起点和终点,由起点和终点建立一个方向向量.沿着方向向量,以夹角追踪的方式查找其它的边界点,直到起点和终点在同一三角形中.根据三角网格所具有的特征,设计了新的区域边界光顺算法和域内顶点的查找方法.部分典型算例表明了该设计算法的正确性和有效性.     

基于形状-空间关系的图像检索技术

针对实际问题,提出一种新的图像检索方法,通过对图像进行小波变换,获得形状和空间关系的综合特征,对综合特征进行归一化处理,并将其作为图像相似性的衡量依据。实验证明,基于形状和空间关系综合特征的图像检索具有很好的效果。     

三角网格模型的基本群分割

提出一种有效的三角网格模型分割方法。用Dijkstra算法求出三角网格模型上任意给定一个基点到其余顶点的最短路径树;求出该模型对偶图的最大生成树,且对偶图的边与该最短路径树的边不相交;找出该模型上所有既不属于最短路径树也不和最大生成树相交的边,这些边分别与最短路径树组成的最短环集合就是给定基点处的基本群,沿着这些最短环就可以把网格分割成一个拓扑同胚于圆盘的区域。实验结果表明,该分割方法可以快速、有效地实现网格的分割。     

曲线拟合的模糊医学图像分割算法

针对由于机体组织间的连续造成医学图像区域边界的模糊性,导致完全自动的医学图像分割算法往往不能取得满意分割效果的问题,提出了一种基于径向基函数曲线拟合的交互式模糊医学图像分割算法。首先由用户在感兴趣的区域交互地选取一些特征点,然后利用径向基函数构造一个三维空间的隐式曲面,使该曲面上的某一等值线即为分割出的区域,文中还提出了两种不同的加速算法。大量实验表明,该算法能有效处理非常模糊的医学图像。     

Iterative infrared ship target segmentation based on multiple features

This paper presents an efficient method for ship target segmentation in infrared (IR) images. It consists of mainly two procedures: iterative image segmentation and ship target selection. First, based on the intensity distribution of an IR image, we design a global background subtraction filter (GBSF) to suppress the background, and an adaptive row mean subtraction filter (ARMSF) to enhance the target. After iteratively applying these two filters, we can obtain a proper threshold for image segmentation. Second, based on the geometric properties of the ship target, we construct four shape features and a selection criterion to identify the real target and remove the non-target regions. Experimental results demonstrate that the proposed method can effectively segment ship targets from different backgrounds in IR images. The advantage of the proposed method over the others in the previous literatures is validated in both visual and quantitative comparisons, especially for IR images with low contrast and uneven intensities.     

Enhancing 3D mesh topological skeletons with discrete contour constrictions

This paper describes a unified and fully automatic algorithm for Reeb graph construction and simplification as well as constriction approximation on triangulated surfaces. The key idea of the algorithm is that discrete contours – curves carried by the edges of the mesh and approximating the continuous contours of a mapping function – encode both topological and geometrical shape characteristics. Therefore, a new concise shape representation, enhanced topological skeletons, is proposed, encoding the contours’ topological and geometrical evolution. First, mesh feature points are computed. Then they are used as geodesic origins for the computation of an invariant mapping function that reveals the shape most significant features. Next, for each vertex in the mesh, its discrete contour is computed. As the set of discrete contours recovers the whole surface, each of them can be analyzed, both to detect topological changes and constrictions. Constriction approximations enable Reeb graphs refinement into more visually meaningful skeletons, which we refer to as enhanced topological skeletons. Extensive experiments showed that, without any preprocessing stage, proposed algorithms are fast in practice, affine-invariant and robust to a variety of surface degradations (surface noise, mesh sampling and model pose variations). These properties make enhanced topological skeletons interesting shape abstractions for many computer graphics applications.     

大型数据库中基于邻域连接的层次聚类算法

提出了一种基于邻域连接的层次聚类算法HANL,该算法首先采用分割的方法将数据集划分为若干个子簇,通过对子簇间的连接的分析,建立子簇间的连接构成图,图中带权的边代表了子簇间的连接紧密度。合并连接紧密度高的结点,得到最后的聚类结果。该算法适用于高维数据集,能够对任意形状的簇进行聚类,无论对于数值属性的数据库还是分类属性的数据库都是一个有效的聚类方法。同时这种方法聚类速度快,效率高,具有良好的伸缩性。     

The progressive mesh compression based on meaningful segmentation

Nowadays, both mesh meaningful segmentation (also called shape decomposition) and progressive compression are fundamental important problems, and some compression algorithms have been developed with the help of patch-type segmentation. However, little attention has been paid to the effective combination of mesh compression and meaningful segmentation. In this paper, to accomplish both adaptive selective accessibility and a reasonable compression ratio, we break down the original mesh into meaningful parts and encode each part by an efficient compression algorithm. In our method, the segmentation of a model is obtained by a new feature-based decomposition algorithm, which makes use of the salient feature contours to parse the object. Moreover, the progressive compression is an improved degree-driven method, which adapts a multi-granularity quantization method in geometry encoding to obtain a higher compression ratio. We provide evidence that the proposed combination can be beneficial in many applications, such as view-dependent rendering and streaming of large meshes in a compressed form.     

Cropping-resilient 3D mesh watermarking based on consistent segmentation and mesh steganalysis

Multimedia Tools and Applications - This paper presents a new approach to 3D mesh watermarking using consistent segmentation and mesh steganalysis. The method is blind, statistical, and highly...     

网格分割的3维网格模型非盲水印算法

目的 信息技术的发展使得面向3维模型版权保护的问题越来越突出,提出一种新的基于网格分割的3维网格模型非盲水印算法。方法 首先使用基于形状直径函数的网格分割算法对3维网格模型进行有意义的网格分割,然后计算每个分块的鲁棒重心并以此为中心将模型由直角坐标系转换到球面坐标系,最后通过调制每个顶点范数的分布来嵌入水印,在水印检测阶段使用非盲检测的方法提取水印。结果 针对目前基于网格分块的水印算法的网格分割不一致以及对分割边界依赖性过强等问题,引入基于形状直径函数的网格分割算法并在重对齐、重采样过程中加入待检测模型与原始模型分块匹配过程以保证网格分割的一致性,并且选取分块的顶点范数的分布作为水印嵌入基元,使得算法能够有效地减弱对分割边界的依赖性。结论 实验结果表明,该算法可以有效抵抗平移、旋转、缩放、噪声、细分、简化、剪切等常见的攻击以及多种攻击的联合攻击。     

基于多尺度曲面拟合的细胞图像表面分割算法

针对不规则多形变形状变化特征的红血球细胞分类识别问题,提出一种基于阴影形状恢复技术与多尺度曲面拟合相结合的复杂表面分割方案.利用Shape from Shading进行重建得到的细胞表面三维高度场可用于计算高斯曲率与平均曲率并得到表面类型图像标识的初始分割,然后通过多尺度二元多项式函数分别对不同类型表面进行曲面拟合,得到的分割结果可将不同形状部分区分开来,并以此作为进一步对细胞进行分类的依据.实验结果表明,该方法易于实现,且分割效果较好.     

基于运动历史图像和椭圆拟合的手势分割

针对当前常用的手势分割方法较难适应复杂的光照环境,提出了一种新的方法。该方法先从视频序列获取运动历史图像（Motion History Image,MHI）,对MHI进行运动区域分割,然后在这些运动区域筛选出手势区域。为了克服手势区域分割偏大的问题,提出了利用该区域内的当前运动轮廓做椭圆拟合,进而得到精度更高的手势分割结果。实验结果表明,提出的方法能够有效地分割出手势,并且和传统方法相比较更能适应不同的光照环境。     

Freeform surface flattening based on fitting a woven mesh model

This paper presents a robust and efficient surface flattening approach based on fitting a woven-like mesh model on a 3D freeform surface. The fitting algorithm is based on tendon node mapping (TNM) and diagonal node mapping (DNM), where TNM determines the position of a new node on the surface along the warp or weft direction and DNM locates a node along the diagonal direction. During the 3D fitting process, strain energy of the woven model is released by a diffusion process that minimizes the deformation between the resultant 2D pattern and the given surface. Nodes mapping and movement in the proposed approach are based on the discrete geodesic curve generation algorithm, so no parametric surface or pre-parameterization is required. After fitting the woven model onto the given surface, a continuous planar coordinate mapping is established between the 3D surface and its counterpart in the plane, based on the idea of geodesic interpolation of the mappings of the nodes in the woven model. The proposed approach accommodates surfaces with darts, which are commonly utilized in clothing industry to reduce the stretch of surface forming and flattening. Both isotropic and anisotropic materials are supported.