异种油藏网格模型三维可视化优化方法研究

在油藏三维建模和数值模拟软件中,网格模型在存储格式、网格排序等方面存在较大差异,且大规模网格模型将占用大量存储空间同时需要运算大量数据,限制其绘制速度。为此,提出了异种油藏网格模型三维可视化优化方法,加载异种油藏网格模型,并实现网格模型消隐算法,提高油藏网格模型的绘制速度。实验结果表明,该方法能够加载异种油藏网格模型,与优化前的网格模型相比,优化后的模型在存储、绘制速度和效果上有着明显的优势。     

Coarse-to-fine stereo vision with accurate 3D boundaries

This paper presents methods for efficient recovery of accurate binocular disparity estimates in the vicinity of 3D surface discontinuities. Of particular concern are methods that impact coarse-to-fine, local block-based matching as it forms the basis of the fastest and the most resource efficient stereo computation procedures. A novel coarse-to-fine refinement procedure that adapts match window support across scale to ameliorate corruption of disparity estimates near boundaries is presented. Extensions are included to account for half-occlusions and colour uniformity. Empirical results show that incorporation of these advances in the standard coarse-to-fine, block matching framework reduces disparity errors by more than a factor of two, while performing little extra computation, preserving low complexity and the parallel/pipeline nature of the framework. Moreover, the proposed advances prove to be beneficial for CTF global matchers as well.     

Exploration of 3D grid caching strategies for ray-shooting

Technology evolution gives an easy access to high performance dedicated computing machines using, for example, GPUs or FPGAS. When designing algorithms dealing with highly structured multidimensional data, the real bottleneck is often linked to memory access. The strategies implemented in standard CPU cache architectures are no longer efficient due to the parallelism level and the inherent structure of data. This article presents the so-called “n-Dimensional Adaptive and Predictive Cache” (nD-AP Cache) architecture aiming at efficient data access for grid traversal. A theoretical model of the 3D version of the cache was setup in order to predict the cache efficiency for given statistical characteristics of the access sequences and for given parameters of the cache. The practical example of ray shooting algorithms has been chosen in order to carefully explore the design space and exercise the 3D-AP cache. For this purpose, a simulation model as well as a fully functional emulation platform have been designed. Thanks to the proven efficiency of the architecture further improvement and applications of the nD-AP Cache are discussed. Comparisons with standard caches show that the nD-AP Cache allows to be two times more efficient than an “ideal” associative cache and, this, with four times less memory.     

Local Upsampling Fourier Transform for accurate 2D/3D image registration

An accurate image registration method based on Local Upsampling Fourier Transform (LUFT) is developed in this paper. It uses a hierarchical strategy to estimate more accurate image pair’s registration parameters, which consists of a coarse estimation and a robust and efficient refinement stage as well. The initial parameter is estimated through a conventional Phase Only Correlation (POC) method in the coarse stage, and then it is refined by the Local Upsampling Fourier Transform in frequency domain to achieve higher accuracy. Furthermore, as will be shown in many experiments, the LUFT can achieve more accurate translation and rotation estimation, and it is efficient, robust to noise, and it can be applied to accurate 2D and 3D image rotation and translation estimation.     

Proximity clouds — an acceleration technique for 3D grid traversal

In this paper we present a new method for the acceleration of ray traversal through a regular 3D grid. A distance transformation is precomputed and mapped onto the empty grid space. A ray traversing the empty space is assisted by the distance values which permit it to perform long skips along the ray direction. We show that the City-Block metric simplifies the preprocessing with no penalty at the traversal phase. Different schemes are discussed and the trade-off between the preprocessing time and the speed-up is analyzed.     

A cell-transverse display algorithm for regular and rectilinear 3D grid data

This paper proposes an efficient direct imaging algorithm for constructing iso-surfaces from regular and rectilinear 3D grid data in scientific and engineering visualization. The basic idea is to generate and draw polygons simultaneously by processing the cells spanned by grids in decreasing order of distance from the current viewpoint. Iso-surfaces are generated in five or six tetrahedrons into which the cells are subdivided, and are sent to a graphics device or drawn into a frame buffer on the fly. The execution order of each of the tetrahedrons is identical and is determined by the current viewpoint. Since the algorithm does not need to store intermediate polyhedral data and does not require a depth buffer memory for hidden surface removal, it is applicable to a large quantity of data on a 3D grid, such as computed tomography (CT) data. It is also particularly powerful for semi-transparent display, because transparency calculation can be reduced to image compositing operations if the polygons are drawn in order of their z-depth from the current viewpoint.     

机器人视觉三维重建网格门户的研究与开发

为了提高机器人视觉三维重建的速度,分析了建设机器人视觉三维重建网格的必要性以及网格门户在网格系统中的重要性.根据三维重建网格的特点设计了网格门户的体系结构,介绍了基于Gridport门户开发工具包快速开发三维重建网格门户中的各个组件的基本过程,实现了基于门户的单点登录、用户管理、资源监测、文件传输和三维重建服务调用等基本功能.     

2D structured grid generation method producing a mesh with prescribed properties near boundary

A variational method of generating a structured mesh on a two-dimensional domain is considered. To this end, a quasiconformal mapping of the parametric domain with a given Cartesian mesh onto the underlying physical domain is used. The functions implementing the mapping are sought by solving the Dirichlet problem for the system of elliptic second-order partial differential equations. An additional control for the cell shape is executed by introducing a local mapping which induces a control metric. In some particular cases, instead of an additional local mapping, a global mapping of the parametric domain onto the intermediate domain is used, where the curvilinear mesh is produced, and next this domain is mapped onto the underlying physical domain. The control metric allows to obtain a mesh with required properties: grid line orthogonality and prescribed mesh point clustering near the domain boundary. Examples of mesh in the annulus and near airfoil are presented.     

基于Gridport开发三维重建网格门户的研究

分析了机器人视觉三维重建领域存在的突出问题,提出了解决三维重建速度问题的不同思路,将网格技术引入三维重建领域,具体研究了基于Globus中间件平台,通过Gridport4.0网格门户开发工具包开发面向三维重建的网格门户的过程。     

Quick and accurate estimation of human 3D hand posture

We propose a three-dimensional hand posture estimation system that can retrieve a hand posture image most similar to the input data from a non-multilayer database. Our system uses, at the first stage, coarse screening by the proportional information on the hand images, which roughly correspond to forearm rotation or bending of the thumb or four fingers; then, at the second stage, performs a detailed search for similarity for selected candidates. To describe forearm rotation, and wrist’s internal and external rotations, bending and stretching, no separate processes were used for estimating the corresponding joint angles. By estimating the sequential images of the finger shape using this method, we successfully realized a process involving a joint angle estimation error within two or three degrees, a processing time of approximately 80 fps or more, using only one Note PC and high-speed camera, even when the wrist was freely rotating. Since the image information and the joint angle information are paired in the database, as well as the wrist joint, the system can generate the imitative motions as those of the fingers and wrist of a human being with no time delay by means of a robot, by outputting the estimation results to the robot hand.     

3D conforming power diagrams for radial LGR in CPG reservoir grids

Mesh generation becomes a crucial step in reservoir flow simulation of new generation. The mesh must faithfully represent the architecture of the reservoir and its heterogeneity. In (Flandrin et al. in IJNME 65(10):1639–1672, 2006) a three-dimensional hybrid mesh model was proposed to capture the radial characteristics of the flow around the wells. In this hybrid mesh, the reservoir is described by a non-uniform Cartesian structured mesh and the drainage areas around the wells are represented by structured radial circular meshes. Unstructured polyhedral meshes are used to connect these two kinds of structured grids. The construction of these transition meshes is based on 3D power diagrams (Aurenhammer in SIAM J Comput 16(1):78–96, 1987) to ensure finite volume properties such as mesh conformity, dual orthogonality and cell convexity. In this paper, we propose an extension of this hybrid model to the case where the reservoir is described by a corner point geometry (CPG) grid. At first, the CPG grid is mapped, in a reference space, into a non-uniform Cartesian grid by minimizing the mapping deformation. Then, a hybrid mesh is generated in this reference space using the previous method. Finally, this mesh is mapped back into the real space. Some quality criterions are introduced to measure and improve the quality of the polyhedral transition mesh.     

3D time-domain regular grid infinite element in elastic foundation

The normal dynamic infinite element in elastic foundation cannot be used in time-domain due to it's inclusive frequency term.A novel 3D regular grid infinite element is constructed to deal with the time-domain problem.This new infinite element method can easily transform the frequency terms of mass matrix and stiffness matrix to the terms in higher-order dynamic equation,thus a higher-order dynamic equilibrium equation is formed.Based on the second-order Wilson-θ dynamic equation,a new time-domain numeric f...     

Compression of 3D digital signals based on hierarchical grid interpolation

A method of hierarchical compression of 3D digital signals is considered as a generalization of the familiar image compression method based on the hierarchical grid interpolation to the 3D case. Special attention is paid to constructing 3D interpolation systems. The effectiveness of the method developed here is compared to the prototype using only 2D dependences. Bavrina Alina Yur’evna (b. 1980) graduated from the Samara State Aerospace University (SSAU) in 2003. At present, she is a research scholar at the department of Geoinformatics, SSAU. Her scientific interests include image processing, compression, and geoinformatics. A.Yu.Bavrina has more than 10 publications, including 4 articles. She is a member of the Russian Association for Image Recognition and Analysis. Gashnikov Mikhail Valer’evich (b. 1975) graduated from the Samara State Aerospace University (SSAU) in 1998. In 2004, he defended his Ph.D. (Eng.) thesis. At present, M.V. Gashnikov is an associate lecturer at the Department of Geoinformatics (SSAU). The scope of his scientific interests includes image processing, compression, and statistical coding. He has 30 publications, including 12 papers and a monograph (with coauthors). M.V. Gashnikov is a member of the Russian Association for Image Recognition and Analysis. Sergeyev Vladislav Viktorovich (b. 1951) graduated from the Kuibyshev Aviation Institute (now Samara State Aerospace University) in 1974. In 1993, he defended his D.Sc. (eng.) thesis. At present, V.V. Sergeyev heads the Laboratory of Mathematical Methods of Image Processing at the Institute of Image Processing Systems, Russian Academy of Sciences. His scientific interests include digital signal processing, image analysis, image recognition, and geoinformatics. He has more than 150 publications, including 40 articles and two monographs (with co-authors). V.V. Sergeyev is the chairman of the Povolzh’e Division of the Russian Association for Pattern Recognition and Image Analysis and a Corresponding Member of the Russian Academy of Ecology and the Academy of Engineering Sciences of the Russian Federation, a member of SPIE (International Society for Optical Engineering), and a winner of the Samara Regional Award in Science and Engineering.     

Parameter optimization in 3D reconstruction on a large scale grid

Reaching as high structural resolution as possible in 3D electron microscopy of biological specimens is crucial to understanding their function and interactions. Technical and biological limitations make electron microscopy projections of such specimens quite noisy. Under those circumstances, the broadly used Weighted Back-Projection algorithm presents some limitations for 3D reconstruction. Iterative tomographic reconstruction algorithms are well suited to provide high resolution 3D structures under such noisy conditions. Nevertheless, these iterative algorithms present two major challenges: computational expensiveness and some free parameters which need to be correctly tuned to obtain the best possible resolution. This work applies global optimization techniques to search for the optimal set of parameters and makes use of the high-throughput capabilities of grid computing to perform the required computations. Fault tolerance techniques have been included in our application to deal with the dynamic nature and complexity of large scale computational grids. The approach for parameter optimization presented here has been successfully evaluated in the European EGEE grid, obtaining good levels of speedup, throughput and transfer rates.     

三维重建网格系统中资源调度的研究

网格系统中存在着大量动态、异构的资源,有效的利用这些资源可以达到提高图像三雏重构的速度的目的.设计了图像三维重建系统的资源调度结构,基于该结构提出了改进启发式调度算法,并对算法的执行过程和并行任务集的存储方法进行论述.最后,利用GridSim对调度算法进行仿真测试.仿真测试结果表明,在图像三维重建系统中,改进启发式调度算法比传统的Min-Min算法具有更高的执行效率.     

3D-ARNet: An accurate 3D point cloud reconstruction network from a single-image

Multimedia Tools and Applications - Generating a more realistic 3D reconstruction point cloud is an ill-posed problem. It is a challenging task to infer 3D shape from a single image. In this paper,...     

基于改进调制结构光的三维形状准确测量方法

针对结构光三维形状测量中投射结构光的相互反射而降低形状测量精度的问题,提出一种改进结构光三维形状测量方法.该方法是利用了直接反射和相互反射之间存在的相位差异,以格雷码为基础设计出新的调制结构光;向被测对象投射一系列调制结构光的正-反投影,并利用摄像机获取与其相对应的结构光条纹图像.通过该条纹图像的亚像素定位方法确定结构光的边缘.实验结果表明,该方法能够准确地分离或消除了相互反射,将提高结构光三维形状测量精度.     

Grid-based scan-to-map matching for accurate 2D map building

This paper presents a grid-based scan-to-map matching technique for accurate 2D map building. At every acquisition of a new scan, the proposed technique matches the new scan to the previous scan similarly to the conventional techniques, but further corrects the error by matching the new scan to the globally defined map. In order to achieve best scan-to-map matching at each acquisition, the map is represented as a grid map with multiple normal distributions (NDs) in each cell, which is one contribution of this paper. Additionally, the new scan is also represented by NDs, developing a novel ND-to-ND matching technique. This ND-to-ND matching technique has significant potential in the enhancement of the global matching as well as the computational efficiency. Experimental results first show that the proposed technique accumulates very small errors after consecutive matchings and identifies that the scans are matched better to the map with the multi-ND representation than one ND representation. The proposed technique is then tested in a number of large indoor environments, including public domain datasets and the applicability to real world problems is demonstrated.     

Optimal population codes for space: grid cells outperform place cells

Rodents use two distinct neuronal coordinate systems to estimate their position: place fields in the hippocampus and grid fields in the entorhinal cortex. Whereas place cells spike at only one particular spatial location, grid cells fire at multiple sites that correspond to the points of an imaginary hexagonal lattice. We study how to best construct place and grid codes, taking the probabilistic nature of neural spiking into account. Which spatial encoding properties of individual neurons confer the highest resolution when decoding the animal's position from the neuronal population response? A priori, estimating a spatial position from a grid code could be ambiguous, as regular periodic lattices possess translational symmetry. The solution to this problem requires lattices for grid cells with different spacings; the spatial resolution crucially depends on choosing the right ratios of these spacings across the population. We compute the expected error in estimating the position in both the asymptotic limit, using Fisher information, and for low spike counts, using maximum likelihood estimation. Achieving high spatial resolution and covering a large range of space in a grid code leads to a trade-off: the best grid code for spatial resolution is built of nested modules with different spatial periods, one inside the other, whereas maximizing the spatial range requires distinct spatial periods that are pairwisely incommensurate. Optimizing the spatial resolution predicts two grid cell properties that have been experimentally observed. First, short lattice spacings should outnumber long lattice spacings. Second, the grid code should be self-similar across different lattice spacings, so that the grid field always covers a fixed fraction of the lattice period. If these conditions are satisfied and the spatial "tuning curves" for each neuron span the same range of firing rates, then the resolution of the grid code easily exceeds that of the best possible place code with the same number of neurons.     

Simple and accurate scheme for fluid velocity interpolation for Eulerian-Lagrangian computation of dispersed flows in 3D curvilinear grids

Particle tracking in turbulent flows in complex domains requires accurate interpolation of the fluid velocity field. If grids are non-orthogonal and curvilinear, the most accurate available interpolation methods fail. We propose an accurate interpolation scheme based on Taylor series expansion of the local fluid velocity about the grid point nearest to the desired location. The scheme is best suited for curvilinear grids with non-orthogonal computational cells. We present the scheme with second-order accuracy, yet the order of accuracy of the method can be adapted to that of the Navier-Stokes solver.An application to particle dispersion in a turbulent wavy channel is presented, for which the scheme is tested against standard linear interpolation. Results show that significant discrepancies can arise in the particle displacement produced by the two schemes, particularly in the near-wall region which is often discretized with highly-distorted computational cells.