Cartographic generalization includes the selection of objects and phenomena, as well as their simplification (generalization), to be shown in the map while preserving the main typical traits, characteristics, and corr...
详细信息
Cartographic generalization includes the selection of objects and phenomena, as well as their simplification (generalization), to be shown in the map while preserving the main typical traits, characteristics, and correlations by the criteria set by the user in the request. These criteria include the problem being solved and the scale of the displayed map. Various map transformations can change the relationships between objects, especially since it is common practice to simplify each type of spatial object independently (first the administrative boundaries, then the road network, populated localities, hydrographic network, etc.). The solution of topological conflicts is one of the key problems of generalizing digital map. A great deal of attention has been paid to the solution of this problem since the start of studies in this domain. The consideration of coverings and meshstructures confines the more general problem of managing topological conflicts to solve topological conflicts within a mesh cell. This study proposes a new geometric simplification algorithm. Its feature consists of the joint simplification of a set of spatial objects of various types while preserving their topological relations. The only parameter of the proposed algorithm is the minimal size of the detail shown in the map. Usually, this size is equal to one millimeter in the target map scale. Step one of the algorithm is the construction of a special mesh data structure. This structure is used to form, for each spatial object, a sequence of cells, to which points of this object belong. If a cell contains points of only one object, the object is geometrically simplified within the bounding cell using the sleeve-fitting algorithm. If a cell contains points of several objects, the geometric simplification is done using a special topology-preserving procedure.
We introduce the Stellar decomposition , a model for efficient topological datastructures over a broad range of simplicial and cell complexes. A Stellar decomposition of a complex is a collection of regions indexing ...
详细信息
We introduce the Stellar decomposition , a model for efficient topological datastructures over a broad range of simplicial and cell complexes. A Stellar decomposition of a complex is a collection of regions indexing the complex's vertices and cells such that each region has sufficient information to locally reconstruct the star of its vertices, i.e., the cells incident in the region's vertices. Stellar decompositions are general in that they can compactly represent and efficiently traverse arbitrary complexes with a manifold or non-manifold domain. They are scalable to complexes in high dimension and of large size, and they enable users to easily construct tailored application-dependent datastructures using a fraction of the memory required by a corresponding global topological datastructure on the complex. As a concrete realization of this model for spatially embedded complexes, we introduce the Stellar tree , which combines a nested spatial tree with a simple tuning parameter to control the number of vertices in a region. Stellar trees exploit the complex's spatial locality by reordering vertex and cell indices according to the spatial decomposition and by compressing sequential ranges of indices. Stellar trees are competitive with state-of-the-art topological datastructures for manifold simplicial complexes and offer significant improvements for cell complexes and non-manifold simplicial complexes. We conclude with a high-level description of several mesh processing and analysis applications that utilize Stellar trees to process large datasets.
In the traditional programming paradigm, datastructures and algorithms are developed for specific data types and requirements. This leads to code redundancy and inflexibility, thus not allowing effective code reuse f...
详细信息
In the traditional programming paradigm, datastructures and algorithms are developed for specific data types and requirements. This leads to code redundancy and inflexibility, thus not allowing effective code reuse for similar applications. One effective approach to increase code reuse is generic programming, which focuses on the development of efficient, reusable software libraries through suitable abstractions for the common requirements. In this paper, we present how we applied generic programming to an ongoing effort for mesh-based adaptive simulations on massively parallel computers. Three generic components, iterator, set and tag, were developed using design pattern, C++ template programming and the standard template library. The scaling studies on petascale supercomputers demonstrate the efficiency of the reusable, generic components which do not sacrifice the performance of the previous tools developed in the traditional object-oriented programming paradigm.
Grid shells are efficient structural systems covering large open spaces with relatively small amount of materials. Also, post forming techniques allow realization of geometrically complex (free-form) shapes by means o...
详细信息
Grid shells are efficient structural systems covering large open spaces with relatively small amount of materials. Also, post forming techniques allow realization of geometrically complex (free-form) shapes by means of standard connection systems. However, due to complexity of the analysis-design process, they are rarely utilized in construction design. In this paper, a 'facilitating' numerical framework is introduced in which, for a given continuous reference shape, a geometrically similar discrete model is found by implementation of a six degree of freedom formulation of the Dynamic Relaxation method, to handle members bending and torsional stiffness. A grid cutting pattern algorithm is introduced, as well as methods to numerically simulate the double-layer construction technique and a novel (single-node) cylindrical joint model. The methods are extensively tested and validated on a range of structures, from 'simple' single-rod cases to more complex, actively bent, grid shell frameworks. (C) 2014 Elsevier Ltd. All rights reserved.
A mesh insertion method is presented to merge a tool mesh into a target mesh. All the entities of the tool mesh are preserved in the output mesh while some of the entities of the target mesh are modified or eliminated...
详细信息
ISBN:
(数字)9783642043192
ISBN:
(纸本)9783642043185
A mesh insertion method is presented to merge a tool mesh into a target mesh. All the entities of the tool mesh are preserved in the output mesh while some of the entities of the target mesh are modified or eliminated in order to obtain a topologically conforming mesh. The algorithm can handle non-manifold surfaces formed of quadrilaterals and/or triangles as well as volumetric meshes based on hexahedra, prisms, pyramids and/or tetrahedra. Lower order elements such as beams can also be taken into consideration. A robust 2-steps advancing front algorithm is introduced to fill the narrow gap between the two mesh objects to obtain a complete crack-free connection. An efficient mesh data structure is developed to optimize the search operations and the intersection tests needed by the algorithm. Several application examples are provided to show the strength of the presented algorithm.
Automatically generated or laser-scanned surfaces typically exhibit large clusters with a uniform pattern. To take advantage of the regularity within clusters and still be able to edit without decompression, we develo...
详细信息
ISBN:
(纸本)9781568812656
Automatically generated or laser-scanned surfaces typically exhibit large clusters with a uniform pattern. To take advantage of the regularity within clusters and still be able to edit without decompression, we developed a two-level datastructure that uses an enumeration by orbits and an individually adjustable stencil to flexibly describe connectivity. The structure is concise for storing mesh connectivity; efficient for random access, interactive editing, and recursive refinement; and it is flexible by supporting a large assortment of connectity patterns and subdivision schemes.
暂无评论