共查询到17条相似文献，搜索用时 171 毫秒
1.
为实现大规模地形的多分辨率显示与实时绘制,基于LOD技术给出了多尺度TIN的管理和表达算法。探讨该算法相关的数据组织、LOD层次表达、实时刷新等关键问题。该算法使用分级策略,在不影响视觉效果前提下对TIN进行分级表达;使用分区策略,在可视化过程中对TIN进行局部更新。采取不同分辨率TIN模型间逐步过渡策略,基本上消除了视图变换时的跳跃感。实验结果表明,这种紧凑有效的TIN表示方法实现简单,内存开销较少,CPU耗费小,大大缩短了视图刷新切换时间,能够在普通机器上实现大规模地形的实时漫游。 相似文献
2.
虚拟地形环境在游戏、仿真、虚拟现实等领域有广泛的应用,在网络环境下如何进行海量地形数据的三维表达与传输是目前研究的重点。基于对等思想提出一种适合大规模地形漫游的分布式网络结构,充分发挥客户机的作用,从而有效地减少服务器负载,采用多点下载数据,提高地形数据的传输速度。同时研究该网络结构下多点下载模型、数据预处理、数据流程和视点相关的LOD简化算法,实现网络环境下大规模地形实时漫游。实验结果表明,在分布式网络环境下,该文中提出的方案可实现大规模地形实时漫游。 相似文献
3.
基于山地灾害动态过程仿真需要的考虑,并针对该动态过程仿真时渲染数据量过大所造成的实时性较差的问题,提出了利用改进的三角形二叉树LOD算法实现地形三维建模与可视化的方法。算法对山地地形数据进行了分层和分块的预处理,用三角形二叉树表示地形网格,并结合视点和局部地形的粗糙程度,动态的载入所需的地形块和释放无用的地形块,使得内存中的地形数据维持在一定范围内。实验结果表明;在对地形渲染不失真的前提下,本方法能够有效地提高地形绘制的效率,可应用到大规模山地地形的三维建模与可视化中去,为整个山地灾害的动态过程仿真奠定了良好的基础。 相似文献
4.
《地理与地理信息科学》2016,(1)
地貌演化等地表过程的分析模拟实时产生系列地形数据,该动态过程的可视化对性能要求较高,传统基于预处理的方法计算量大、绘制延迟明显。面向大规模动态地形可视化,提出一种LOD预处理与实时更新相结合的混合调度技术,基于场景图对动态地形LOD建模与组织,建立多线程模型实现地形瓦片的动态更新和绘制。对于每次迭代计算产生的新地形,该方法以LOD瓦片的动态调度替代传统的静态预处理方法,与地表过程计算同步更新瓦片,且仅重新计算和渲染当前视域和分辨率下地形发生变化的局部瓦片,通过LOD的局部动态更新避免可视化数据的全局重新生成,显著降低过程模型计算和结果更新对渲染过程的影响,提高整体的可视化性能。 相似文献
5.
大规模地形漫游中的实时LOD算法研究 总被引：10，自引：1，他引：9
大规模地形漫游在游戏、仿真、虚拟现实等领域有着广泛的应用。该文在总结现有地形简化算法的基础上,提出了一种基于动态调度的地形块内视点相关二叉树简化算法,有效地简化地形,实现大规模场景的实时漫游。 相似文献
6.
将地貌综合的三维Douglas-Peucker方法引入地形LOD中,通过构建Quad_TIN模型,结合离散点的全局重要性分级、地形块的四叉树模型构建、高效的可见性判断及增量更新等策略,提出一种大规模地形实时动态显示的新算法。实验结果表明,在保证地形的自适应快速、逼真显示的前提下,可大大扩展三维Douglas-Peucker和Quad_TIN的适用范围及运算效率,为海量三维场景的逼真快速重构提供了现实可能性。 相似文献
7.
一种快速地形纹理生成和虚拟漫游方法 总被引：3，自引：1，他引：2
复杂场景的大范围、高分辨率纹理的快速漫游是虚拟现实、GIS、仿真等领域的关键技术与难点。DEM是对地形地貌的数字描述和模拟,利用DEM数据生成可视化地形,可以更好的描述特定区域的地形特征,通过对特定区域中模型的纹理生成和映射,配合光照、大气等区域内自然场景的建模技术,可生成较为逼真的真实场景。基于OpenGL编程进行DEM地形可视化是实现地形实时漫游的方法之一,利用层次细节模型降低场景复杂度以提高漫游帧速率是该类系统中的常用方法,由于场景复杂度问题,不同的系统在具体算法实现中采用的方法也不尽相同。本文以一个虚拟校园为例,针对DEM数据转换和LOD模型面临的问题,给出了特定场景的LOD模型数据处理思想和纹理快速纹理生成、匹配、映射算法。同时给出虚拟实时漫游中第一人称漫游和飞行漫游的一般方法,讨论了在Windows环境下使用OpenGL进行虚拟漫游的基本步骤。提出了一种新的根据场景特点快速生成和映射纹理途径。结果表明,该方法在保证真实感条件情况下达到了满意的实时漫游效果。 相似文献
8.
《地理与地理信息科学》2015,(4)
为了从格网剖分结构上解决分块LOD(Level Of Details)模型中复杂的块内、块间裂缝问题,避免目前裂缝消除方法的缺陷,该文提出一种基于多分辨率半边结构的分块LOD模型无缝表达方法。首先,引入多分辨率组合映射理论,给出基于多分辨率半边的菱形块多尺度表达的基本方法,包括菱形块剖分方法和编码方法;在此基础上,提出块内、块间格网无缝表达机制,设计并实现了基于菱形块的全球地形动态LOD管理机制;最后,应用C语言和DirectX工具,开发了相应的可视化实验系统。实验表明:该方法从格网剖分结构上解决了全球地形分块LOD模型中的块内、块间裂缝问题;与传统方法相比,其不需要限制相邻格网的剖分层差,简化效率更高,且无地形失真。 相似文献
9.
大尺度分布式水文模型数字流域 提取方法研究 总被引：11，自引：1，他引：10
构建大尺度分布式水文模型是当前大气水文模型耦合研究的一项重要内容。本文介绍一 种根据1km DEM 生成更大网格尺度DEM 数据, 同时可以保持流域河网信息并减缓高程、坡度 等地貌参数信息量衰减速度的有效方法———ZB算法。利用该方法和常规的网格平均法生成黄河 唐乃亥以上流域的5km、10km、15km 和20km 两套DEM 数据, 分别提取高程、坡度、地形指数、河 网密度、主河道长度、流域面积等流域特征参数, 并与1km DEM 提取的上述参数进行比较, 对两 种方法作出评价。结果显示, 随着网格尺度的增大, ZB 算法获得的DEM 数据可以保持河网的连 续性, 提取出合理的流域范围, 减缓地形信息量的衰减速度。该方法满足构建大尺度分布式水文 模型提取数字流域的需要。 相似文献
10.
在分析现有非结构化网格剖分算法的基础上,提出了一种GIS支持下的改进分治算法实现约束Delaunay三角网格剖分.该方法利用了GIS的空间拓扑关系对算法输入数据进行预处理,基于三角形的统一数据结构实现了网格细化,对输出剖分网格进行准确的拓扑和约束条件的检查,并基于推进阵面算法思想,结合空间邻近拓扑关系实现了三角剖分节点和网格的重新编号,方便了实际问题中开边界条件的赋值,提高了计算效率.实例应用表明,该方法大大简化了数值模型非结构化网格剖分的前处理过程,集成了几种综合算法的优点,在保证原分治算法时间复杂度的基础上,提高了约束条件下Delaunay三角网格生成的质量. 相似文献
11.
N. Coll N. Madern J. A. Sellarès 《International journal of geographical information science》2013,27(10):1115-1134
Visibility computation on terrain models is an important research topic with many applications in Geographical Information Systems. A multi‐visibility map is the subdivision of the domain of a terrain into regions that, according to different criteria, encodes the visibility with respect to a set of view elements. We present an approach for visualising approximated multi‐visibility maps of a triangulated terrain corresponding to a set of view elements by using graphics hardware. Our method supports heterogeneous sets of view elements containing points, segments, polygonal chains and polygons and works for weak and strong visibility. Moreover, we are also able to efficiently solve approximated point and polygonal region multi‐visibility queries. To illustrate the usefulness of our approach we present results obtained with an implementation of the proposed algorithms. 相似文献
12.
Mengyun Zhou Jianya Gong 《International journal of geographical information science》2016,30(11):2208-2229
Polygonal vector data are important for representing countries, lakes, residential settlements, and other polygonal features. The proper representation of polygonal vector data is the basis of efficient rendering and picking and quick access and display of the analysis results based on polygons (e.g., 3D overlaying and surface area measurement in mountainous areas) in a virtual globe. However, polygonal vector data are displayed using texture-based or boundary-based approaches in most existing virtual globes. The texture-based approach cannot easily support interactive operations (e.g., picking) and spatial analysis (e.g., adjacency analysis and spatial measurement). The boundary-based approach treats the holes as independent features; however, it is difficult to recognize which boundaries constitute a polygon. Further research is needed on how to better organize the polygons to support efficient rendering, picking, and analysis in a virtual globe. In this article, we propose two methods to drape interior filled 2D polygons onto a multi-resolution 3D terrain. Both proposed methods combine polygon clipping and polygon triangulation. The difference between the two methods is in the way holes are eliminated. Method 1 recursively subdivides a terrain triangle until the child-triangles contain no holes; every resulting clipped polygon, which is then triangulated, contains no holes. Method 2 directly clips a polygon against a terrain triangle and creates bridge edges to transform the resulting polygons with holes to degenerate polygons that are further triangulated. The experimental results demonstrate that both proposed methods can efficiently process polygons with holes resulting in appropriate numbers of triangles. The processed interior-filled polygons remain close to the terrain surface in a virtual globe. Both proposed methods support real-time rendering of polygonal vector data in a virtual globe. 相似文献
13.
该文对基于局部误差、曲率和法向量的5个地形简化指标进行分析评价,用离散的高斯合成曲面来模拟真实DEM,以解析得到的高斯曲率作为地形简化指标“真值”,通过对各个指标“保特征性”可信度的分析,获得对这5个指标的整体评价：1)基于法向量的地形简化指标更能反映地形特征;2)各指标的“保特征性”随简化比的减小呈线性上升;3)各指标的优劣排序对地表形状和分辨率不敏感;4)各指标“保特征性”可信度在同一分辨率下较为稳定。并用实例验证结论的正确性。 相似文献
14.
Çetin Koca 《International journal of geographical information science》2014,28(9):1821-1847
Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time. 相似文献
15.
Jiangfeng She Chuang Li Jiaqi Li Qiujun Wei 《International journal of geographical information science》2018,32(3):476-497
With the extensive application of virtual geographic environments and the rapid development of 3D visualization analysis, the rendering of complex vector lines has attracted significant attention. Although there are many rendering algorithms in 3D geographic information system (GIS), they are not sufficiently flexible to meet the requirements for rendering linear symbols composed of diverse colors and shapes. However, the interactive rendering of a scene and the accuracy of the symbols are important components for large-scale, complex vector lines. In this paper, we propose a graphics processing unit (GPU)-accelerated algorithm for rendering linear symbols on 3D terrain. Symbol rendering is embedded within the terrain-rendering process, and vector lines are encoded in a 3D texture and then transferred to the GPU. A set of visual properties are used to enrich the expression of symbols with the help of geometric operations in the fragment shader. A series of experiments demonstrate that the proposed method can be utilized for drawing various pixel-exact linear symbols and can achieve real-time rendering efficiency. 相似文献
16.
Andrej Osterman Lucas Benedičič Patrik Ritoša 《International journal of geographical information science》2014,28(11):2304-2327
A rapid and flexible parallel approach for viewshed computation on large digital elevation models is presented. Our work is focused on the implementation of a derivate of the R2 viewshed algorithm. Emphasis has been placed on input/output (IO) efficiency that can be achieved by memory segmentation and coalesced memory access. An implementation of the parallel viewshed algorithm on the Compute Unified Device Architecture (CUDA), which exploits the high parallelism of the graphics processing unit, is presented. This version is referred to as r.cuda.visibility. The accuracy of our algorithm is compared to the r.los R3 algorithm (integrated into the open-source Geographic Resources Analysis Support System geographic information system environment) and other IO-efficient algorithms. Our results demonstrate that the proposed implementation of the R2 algorithm is faster and more IO efficient than previously presented IO-efficient algorithms, and that it achieves moderate calculation precision compared to the R3 algorithm. Thus, to the best of our knowledge, the algorithm presented here is the most efficient viewshed approach, in terms of computational speed, for large data sets. 相似文献
17.
Yanli Zhao Anand Padmanabhan 《International journal of geographical information science》2013,27(2):363-384
Viewshed analysis, often supported by geographic information system, is widely used in many application domains. However, as terrain data continue to become increasingly large and available at high resolutions, data-intensive viewshed analysis poses significant computational challenges. General-purpose computation on graphics processing units (GPUs) provides a promising means to address such challenges. This article describes a parallel computing approach to data-intensive viewshed analysis of large terrain data using GPUs. Our approach exploits the high-bandwidth memory of GPUs and the parallelism of massive spatial data to enable memory-intensive and computation-intensive tasks while central processing units are used to achieve efficient input/output (I/O) management. Furthermore, a two-level spatial domain decomposition strategy has been developed to mitigate a performance bottleneck caused by data transfer in the memory hierarchy of GPU-based architecture. Computational experiments were designed to evaluate computational performance of the approach. The experiments demonstrate significant performance improvement over a well-known sequential computing method, and an enhanced ability of analyzing sizable datasets that the sequential computing method cannot handle. 相似文献