基于DEM格网的改进型A*路径搜索算法

为解决DEM格网上的路径搜索问题,分析了DEM格网和道路拓扑网络的共性与区别,并结合DEM格网的特点对比了Dijkstra算法和A*算法的优缺点,提出了基于DEM格网的改进型A*路径搜索算法。该算法充分考虑DEM格网上的路径可达条件,采用移动窗口法获取搜索网格候选集,并根据地理空间分布特征选取A*算法的估价函数,同时引入贪婪准则缩小搜索范围,降低问题复杂度。结合实例对算法进行了实验分析,验证结果表明了该算法的可行性和有效性。     

A three-dimensional numerical manifold method based on tetrahedral meshes

A three-dimensional NMM based on tetrahedral meshes is developed in this paper. First, the displacement functions of manifold elements are formulated by the partition of unity function. Then, the global equilibrium equations for three-dimensional elasto-statics problem are established by minimizing the total potential energy. The stiffness matrix, loading matrix, displacement resistance matrix are derived for program coding. Thereafter, the computational cost of the global stiffness matrix in the NMM is discussed and compared with that in the classical finite element techniques. Finally, two typical examples are investigated to demonstrate the validity of the proposed method. The results indicate that an enough accuracy of approximation will be obtained with decreasing size of the mathematical mesh. The proposed method can be used as potentially powerful tool for three-dimensional structural analysis.     

Parallel construction of Hamiltonian paths for conforming tetrahedral meshes

In this paper, we address the construction of a Hamiltonian path for conforming tetrahedral meshes on distributed memory machines. The path is constrained to pass from one element to the next one through a vertex. For a conforming tetrahedral mesh whose dual graph is connected, if it can be split into many submeshes and the dual graphs of these submeshes are connected, then we can construct partial Hamiltonian paths for all submeshes independently and a Hamiltonian path for the mesh can be obtained by connecting these partial Hamiltonian paths.     

On an automatically parallel generation technique for tetrahedral meshes

A program for the efficient parallel generation of tetrahedral meshes in a wide class of three-dimensional domains having a generalized cylindrical shape is presented. The applied mesh generation strategy is based on the decomposition of some 2D-reference domain into simply connected subdomains. By means of the reference triangulations of these subdomains the tetrahedral layers are built up in parallel. Adaptive grid controlling as well as nodal renumbering algorithms are involved. In the paper several examples are included to demonstrate both the capabilities of the program and the adequate handling with the implemented method of parallelization.     

Direct volume rendering of unstructured tetrahedral meshes using CUDA and OpenMP

Direct volume visualization is an important method in many areas, including computational fluid dynamics and medicine. Achieving interactive rates for direct volume rendering of large unstructured volumetric grids is a challenging problem, but parallelizing direct volume rendering algorithms can help achieve this goal. Using Compute Unified Device Architecture (CUDA), we propose a GPU-based volume rendering algorithm that itself is based on a cell projection-based ray-casting algorithm designed for CPU implementations. We also propose a multicore parallelized version of the cell-projection algorithm using OpenMP. In both algorithms, we favor image quality over rendering speed. Our algorithm has a low memory footprint, allowing us to render large datasets. Our algorithm supports progressive rendering. We compared the GPU implementation with the serial and multicore implementations. We observed significant speed-ups that, together with progressive rendering, enables reaching interactive rates for large datasets.     

Discretizations for weighted condition number smoothing on general unstructured meshes

New method for weighted condition number smoothing of general unstructured computational meshes is presented. Its core, proper discretization of weighted smoothness functional, is detailed, options of particular implementation are discussed and demonstrated on general convex polygonal cells in two dimensions. Possible applications of this algorithm are suggested, namely solution-sensitive mesh adaptation (respecting the variation of some variable) and prevention of unwanted smoothing effects on polar meshes.     

Grid-characteristic method using high-order interpolation on tetrahedral hierarchical meshes with a multiple time step

The purpose of the present paper is to develop a grid-characteristic method for high-performance computer systems using unstructured tetrahedral hierarchical meshes, a multiple time step and the high-order interpolation for simulating complex spatial dynamic processes in heterogeneous environments. This method has the precise formulation of contact conditions and is suitable for the physically correct solution of seismology and seismic prospecting problems in complex heterogeneous environments. The use of the hierarchical meshes allows us to take into account a large number of nonhomogeneous inclusions (cracks, cavities, etc.). The use of this grid-characteristic method makes it possible to use a multiple time step and thereby increase productivity and significantly reduce the computation time. The methods developed for high-order interpolation on unstructured tetrahedral meshes can solve the problems of seismology and seismic prospecting with approximation in space of up to the fifth degree (inclusive).     

User controllable anisotropic shape distribution on 3D meshes

Computational Visual Media - This paper presents an automatic method for computing an anisotropic 2D shape distribution on an arbitrary 2-manifold mesh. Our method allows the user to specify the...     

Cell-centered quasi-one-dimensional reconstruction scheme on 3D hybrid meshes

This paper presents a cell-centered conservative scheme based on a quasi-one-dimensional (1D) reconstruction of variables for the solution of a system of hyperbolic equations on 3D unstructured meshes. Only the case of smooth solutions is considered. Test examples are used to demonstrate that the accuracy and computational costs of the studied scheme are about the same as of the vertexcentered EBR scheme and the preferability of the vertex-centered or cell-centered scheme is determined by the prevalent types of elements in the computational mesh.     

Key-components: detection of salient regions on 3D meshes

In this paper, we present a method to detect stable components on 3D meshes. A component is a salient region on the mesh which contains discriminative local features. Our goal is to represent a 3D mesh with a set of regions, which we called key-components, that characterize the represented object and therefore, they could be used for effective matching and recognition. As key-components are features in coarse scales, they are less sensitive to mesh deformations such as noise. In addition, the number of key-components is low compared to other local representations such as keypoints, allowing us to use them in efficient subsequent tasks. A desirable characteristic of a decomposition is that the components should be repeatable regardless shape transformations. We show in the experiments that the key-components are repeatable and robust under several transformations using the SHREC’2010 feature detection benchmark. In addition, we discover the connection between the theory of saliency of visual parts from the cognitive science and the results obtained with our technique.     

基于人物状态自动机的实时动态寻径算法优化

路径搜索是实现游戏中的角色逼真行走的关键技术之一.针对游戏动态路网中寻径极易陷入陷阱且寻径效率不高的问题,将人物状态自动机和加权的LRTA*算法相结合,提出了基于人物状态自动机的实时动态寻径算法.通过改变估价函数值更新规则与解时间和解质量相结合,加快算法收敛速度,并引入人工搜索标志,完成对LRTA*算法的优化.测试结果表明,该算法有效提高了路径搜索的速度,并使搜索得到的路径平滑自然.     

Joint reversible watermarking and progressive compression of 3D meshes

A new reversible 3D mesh watermarking scheme is proposed in conjunction with progressive compression. Progressive 3D mesh compression permits a progressive refinement of the model from a coarse to a fine representation by using different levels of detail (LoDs). A reversible watermark is embedded into all refinement levels such that (1) the refinement levels are copyright protected, and (2) an authorized user is able to reconstruct the original 3D model after watermark extraction, hence reversible. The progressive compression considers a connectivity-driven algorithm to choose the vertices that are to be refined for each LoD. The proposed watermarking algorithm modifies the geometry information of these vertices based on histogram bin shifting technique. An authorized user can extract the watermark in each LoD and recover the original 3D mesh, while an unauthorized user which has access to the decompression algorithm can only reconstruct a distorted version of the 3D model. Experimental results show that the proposed method is robust to several attack scenarios while maintaining a good compression ratio.     

Adaptive coding of generic 3D triangular meshes based on octree decomposition

In this paper, we present an adaptive-coding method for generic triangular meshes including both regular and irregular meshes. Though it is also based on iterative octree decomposition of the object space for the original mesh, as some prior arts, it has novelties in the following two aspects. First, it mathematically models the occupancy codes containing only a single–“1” bit for accurate initialization of the arithmetic coder at each octree level. Second, it adaptively prioritizes the bits in an occupancy code using a local surface smoothness measure that is based on triangle areas and therefore mitigates the effect of non-uniform vertex sampling over the surface. As a result, the proposed 3D mesh coder yields outstanding coding performance for both regular and irregular meshes and especially for the latter, as demonstrated by the experiments.     

Gossiping on meshes and tori

Algorithms for performing gossiping on one- and higher-dimensional meshes are presented. As a routing model, the practically important wormhole routing is assumed. We especially focus on the trade-off between the start-up time and the transmission time. For one-dimensional arrays and rings, we give a novel lower bound and an asymptotically optimal gossiping algorithm for all choices of the parameters involved. For two-dimensional meshes and tori, a simple algorithm composed of one-dimensional phases is presented. For an important range of packet and mesh sizes, it gives clear improvements upon previously developed algorithms. The algorithm is analyzed theoretically and the achieved improvements are also convincingly demonstrated by simulations, as well as an implementation on the Paragon. On the Paragon, our algorithm even outperforms the gossiping routine provided in the NX message-passing library. For higher-dimensional meshes, we give algorithms which are based on an interesting generalization of the notion of a diagonal. These algorithms are analyzed theoretically, as well as by simulation     

A topological hierarchy for functions on triangulated surfaces

We combine topological and geometric methods to construct a multiresolution representation for a function over a two-dimensional domain. In a preprocessing stage, we create the Morse-Smale complex of the function and progressively simplify its topology by cancelling pairs of critical points. Based on a simple notion of dependency among these cancellations, we construct a hierarchical data structure supporting traversal and reconstruction operations similarly to traditional geometry-based representations. We use this data structure to extract topologically valid approximations that satisfy error bounds provided at runtime.     

Parallel divide and conquer on meshes

We address the problem of mapping divide-and-conquer programs to mesh connected multicomputers with wormhole or store-and-forward routing. We propose the binomial tree as an efficient model of parallel divide-and-conquer and present two mappings of the binomial tree to the 2D mesh. Our mappings exploit regularity in the communication structure of the divide-and-conquer computation and are also sensitive to the underlying flow control scheme of the target architecture. We evaluate these mappings using new metrics which are extensions of the classical notions of dilation and contention. We introduce the notion of communication slowdown as a measure of the total communication overhead incurred by a parallel computation. We conclude that significant performance gains can be realized when the mapping is sensitive to the flow control scheme of the target architecture