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The objective of this paper is to analyze the impact of liquid surface tension on force measurement in submerged micromanipulation. First, at present, mechanical characterization of biological objects in biological liquid is of significant interest. Second, the reduction of the surface force and adhesion forces in a submerged medium could be a relevant approach to perform reliable artificial objects micromanipulation. In both cases, the micro-nano force measurement in a liquid is a great challenge. In the case of a force sensor placed out of the liquid, the measurement is disturbed by the liquid surface tension. This paper proposes an analysis of these disturbances on force measurements. Some design rules are proposed to reduce disturbances. We show that the major disturbances are induced by the contact angle hysteresis, and a complete method is proposed to calculate these disturbances in a micromanipulation task. 相似文献
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Ragini Choudhury Santanu Chaudhury J.B. Srivastava 《Journal of Mathematical Imaging and Vision》2001,14(1):5-20
In this paper we propose a reconstruction based recognition scheme for objects with repeated components, using a single image of such a configuration, in which one of the repeated components may be partially occluded. In our strategy we reconstruct each of the components with respect to the same frame and use these to compute invariants.We propose a new mathematical framework for the projective reconstruction of affinely repeated objects. This uses the repetition explicitly and hence is able to handle substantial occlusion of one of the components. We then apply this framework to the reconstruction of a pair of repeated quadrics. The image information required for the reconstruction are the outline conic of one of the quadrics and correspondence between any four points which are images of points in general position on the quadric and its repetition. Projective invariants computed using the reconstructed quadrics have been used for recognition. The recognition strategy has been applied to images of monuments with multi-dome architecture. Experiments have established the discriminatory ability of the invariants. 相似文献
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Rickard Brüel-Gabrielsson Vignesh Ganapathi-Subramanian Primoz Skraba Leonidas J. Guibas 《Computer Graphics Forum》2020,39(5):197-207
We present an approach to incorporate topological priors in the reconstruction of a surface from a point scan. We base the reconstruction on basis functions which are optimized to provide a good fit to the point scan while satisfying predefined topological constraints. We optimize the parameters of a model to obtain a likelihood function over the reconstruction domain. The topological constraints are captured by persistence diagrams which are incorporated within the optimization algorithm to promote the correct topology. The result is a novel topology-aware technique which can (i) weed out topological noise from point scans, and (ii) capture certain nuanced properties of the underlying shape which could otherwise be lost while performing surface reconstruction. We show results reconstructing shapes with multiple potential topologies, compare to other classical surface construction techniques, and show the completion of real scan data. 相似文献
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一个完整的基于轮廓的曲面重建方法必须建立轮廓对应、解决分支和三角面片的构建.然而大多数已有的曲面重建算法只能解决问题的某些方面,从而导致这些算法不能有效地运用到复杂曲面重建,比如用磁共振获取的人大脑序列切片等盘旋且多分支凸包数据.提出了一个基于Voxel(像素)编码技术的曲面重建算法,该算法能以一种完全自动的方式处理带有空洞的复杂多分支曲面.首先将两相邻断层轮廓投影到定位于中间的一个辅助平面上,求得其差区域,然后根据差区域的不同情形进行分组.对每组轮廓,从对应的差邻域中提取骨架,并用骨架来度量两轮廓的不相似量,对不相似的进行剪支分解,从而使不相似的、复杂的轮廓转换为简单且相似的骨架轮廓对,最后完成三角片构建.重建曲面由二维流体三角面片组成,且仅经过切片上的输入廓线.算法已用手工数据和复杂人脑皮层的磁共振数据进行了仿真测试,检验了算法的有效性. 相似文献
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Yi‐Ling Chen Tung‐Ying Lee Bing‐Yu Chen Shang‐Hong Lai 《Computer Graphics Forum》2011,30(7):2003-2010
In this paper, we propose bipartite polar classification to augment an input unorganized point set ? with two disjoint groups of points distributed around the ambient space of ? to assist the task of surface reconstruction. The goal of bipartite polar classification is to obtain a space partitioning of ? by assigning pairs of Voronoi poles into two mutually invisible sets lying in the opposite sides of ? through direct point set visibility examination. Based on the observation that a pair of Voronoi poles are mutually invisible, spatial classification is accomplished by carving away visible exterior poles with their counterparts simultaneously determined as interior ones. By examining the conflicts of mutual invisibility, holes or boundaries can also be effectively detected, resulting in a hole‐aware space carving technique. With the classified poles, the task of surface reconstruction can be facilitated by more robust surface normal estimation with global consistent orientation and off‐surface point specification for variational implicit surface reconstruction. We demonstrate the ability of the bipartite polar classification to achieve robust and efficient space carving on unorganized point clouds with holes and complex topology and show its application to surface reconstruction. 相似文献
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基于混合训练方法的RBF神经网络的曲面重构 总被引:1,自引:0,他引:1
根据径向基函数神经网络(RBFNN)具有很强的非线性逼近能力,以及强大的抗噪、修复能力等优点,讨论了目前神经网络训练方法,提出将径向基函数神经网络应用于带有噪声数据散乱数据点自由曲面的重构,并对该方法理论上的可行性和实践上的实用性进行了讨论和验证。结果表明:径向基函数网络用于曲面重构, 不仅能够有效地逼近不完善的、带有噪声的曲面,而且拟合精度高、网络的训练速度快,说明了径向基函数神经网络应用于曲面重构问题的可行性,为解决反向工程的技术关键——自由曲面重构提供了一个新的途径。 相似文献
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提出一种基于先进的凸优化技术的光度立体视觉重建框架. 首先通过鲁棒的主成分分析(Robust principle component analysis, RPCA)祛除图像噪声, 得到低秩矩阵和物体表面向量场, 然后再通过表面重建算法从向量场来恢复物体形状. 相对于先前的一些使用最小二乘或者一些启发式鲁棒技术的方法, 该方法使用了所有可用的信息, 可以同时修复数据中的丢失和噪声数据, 显示出了较高的计算效率以及对于大的稀疏噪声的鲁棒性. 实验结果表明, 本文提出的框架大大提高了在噪声存在情况下物体表面的重建精度. 相似文献
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Screened Poisson surface reconstruction robustly creates meshes from oriented point sets. For large datasets, the technique requires hours of computation and significant memory. We present a method to parallelize and distribute this computation over multiple commodity client nodes. The method partitions space on one axis into adaptively sized slabs containing balanced subsets of points. Because the Poisson formulation involves a global system, the challenge is to maintain seamless consistency at the slab boundaries and obtain a reconstruction that is indistinguishable from the serial result. To this end, we express the reconstructed indicator function as a sum of a low-resolution term computed on a server and high-resolution terms computed on distributed clients. Using a client–server architecture, we map the computation onto a sequence of serial server tasks and parallel client tasks, separated by synchronization barriers. This architecture also enables low-memory evaluation on a single computer, albeit without speedup. We demonstrate a 700 million vertex reconstruction of the billion point David statue scan in less than 20 min on a 65-node cluster with a maximum memory usage of 45 GB/node, or in 14 h on a single node. 相似文献
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为了简化法向偏差约束条件和优化光滑能量项,提出一种隐式T样条曲面重建算法.首先利用八叉树及其细分过程从采样点集构造三维T网格,以确定每个控制系数对应的混合函数;然后基于隐式T样条曲面建立目标函数,利用偏移曲面点集控制法向,采用广义交叉检验(GCV)方法估计最优光滑项系数,并依据最优化原理将该问题转化为线性方程组求解得到控制系数,从而实现三角网格曲面到光滑曲面的重建.在误差较大的区域插入控制系数进行T网格局部修正,使得重建曲面达到指定精度.该算法使重建曲面C1连续条件得到松弛,同时给出最优的光顺项系数估计,较好地解决了封闭曲面的重建问题.实例结果表明,文中算法逼近精度高,运算速度快,仿真结果逼真. 相似文献
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基于神经网络的NURBS曲面重建 总被引:1,自引:1,他引:0
曲面重建是CAGD中的重点研究课题,而神经网络具有很好的非线性逼近能力,文中将二者结合,给出了一种利用神经网络将三维数据点拟合为NURBS曲面的方法.提出的前馈型神经网络包含四个隐层,其中一层的激活函数为B样条基函数.由数学推导可知,该网络可以表达NURBS曲面,通过对控制顶点及其权重的学习,可以用该网络来重建NURBS曲面.权值的调整通过误差反传与梯度下降法实现.实验结果表明,文中提出的方法是可行的. 相似文献
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基于阴影的三维表面重构技术的概述 总被引:6,自引:2,他引:4
三维表面重构是计算机视觉的主要任务之一。已经发展了各种各样的重构技术,其中利用单幅图像中物体表面明暗变化来恢复其表面形状的技术尤其引人注目,这不仅因为该技术简单易于实现,更重要的是它适用于各种其它方法难以应用的场合,例如,在机载、星载、弹载环境中的利用。论文从SFS问题的研究背景出发,介绍并分析这方面的一些重要进展,通过对各种重构方法的分析与比较,提出SFS问题的研究发展趋势和一些值得研究的方向。 相似文献
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基于散乱点集的曲面重建 总被引:2,自引:0,他引:2
基于散乱点集的曲面重建是计算机图形学和虚拟现实等领域的研究热点.在对基于散乱点集的曲面重建经典算法进行综述的基础上,较详细地讨论了基于成长型神经网络的曲面重建方法和基于法向量场的曲面重建方法. 相似文献
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提出一种新的利用标定图像进行三维测量的方法。利用SIFT算法找到初始的对应点,然后根据这些点生成三维空间中的种子点,再以这些种子点为中心,向外区域增长,直到完成整个物体表面测量。在每次增长的过程中,需要计算增长的三维空间平面在两个相机上的投影之间的图像相关系数。图像相关系数较大时认为是正确的增长,否则是错误的增长。实验证明,使用该方法能够得到很好的三维测量结果。 相似文献
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Zickler Todd E. Belhumeur Peter N. Kriegman David J. 《International Journal of Computer Vision》2002,49(2-3):215-227
We present a method—termed Helmholtz stereopsis—for reconstructing the geometry of objects from a collection of images. Unlike existing methods for surface reconstruction (e.g., stereo vision, structure from motion, photometric stereopsis), Helmholtz stereopsis makes no assumptions about the nature of the bidirectional reflectance distribution functions (BRDFs) of objects. This new method of multinocular stereopsis exploits Helmholtz reciprocity by choosing pairs of light source and camera positions that guarantee that the ratio of the emitted radiance to the incident irradiance is the same for corresponding points in the two images. The method provides direct estimates of both depth and surface normals, and consequently weds the advantages of both conventional stereopsis and photometric stereopsis. Results from our implementation lend empirical support to our technique. 相似文献
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《Real》1998,4(2):159-164
A holographic principle for computer reconstruction of random rough surface (RRS) and determination of the surface parameters is used. The random function describing the surface is expanded in a Fourier series. The scattering from the RRS light field is approximated as a field, obtained as result of diffraction from sinusoidal gratings. The mixed field (obtained from the mixing of the diffracted field and the field of the laser beam) carries information about the phase of each sinusoidal grating. Sections of the diffracted and mixing fields are correspondingly registered by photodiode array. The first, the second and the third diffraction orders from each grating are taken into account for the surface reconstruction. The statistical distribution and the autocorrelation function of the surface height fluctuation are calculated. The surface parameters of mean roughness, root mean square and correlation length are determined. The studied surface, having a Gaussian statistic, is measured [from the work of Daintyet al.Talystep profilometer. The values of the above-mentioned surface parameters calculated in Daintyet al.are in good agreement with those obtained in the present work. 相似文献