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大规模场景的快速绘制是虚拟现实技术重要的研究课题之一.为了加速场景的绘制,一般采用层次细节模型和可见性裁剪方法,但是现有算法在处理大规模场景时存在着局限性.本文提出了一种新的大规模场景快速绘制算法,该算法在场景层次划分的基础上,利用拓扑结构可变的网格简化方法为场景层次计算连续的分层层次细节模型(HLOD);然后在实时绘制阶段,对场景分层层次细节模型进行视点相关的全局和局部细化,并结合快速有效的视域裁剪,从而大大加速了场景绘制速度.实验结果表明该算法是简单有效的,并且算法还可以进一步扩展到外存方式. 相似文献
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提出一种综合考虑移动设备客户端绘制能力和传输速度的混合型远程绘制方法.该方法采用渐进网格得到不同分辨率的细节层次模型,并利用渐进传输机制逐步传输数据,以缓解单次网络负载.服务器端可以根据网络质量状况、移动客户端的处理能力和用户交互请求来选择适宜的三维细节层次模型,提取特征轮廓线并将生成的线条集合传输给客户端进行本地风格化绘制.将该方法应用于考古数字博物馆展示中取得了良好的效果. 相似文献
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近年来随着互联网的普及和相关技术的日益成熟,大规模图数据处理成为新的研究热点.由于传统的如Hadoop等通用云平台不适合迭代式地处理图数据,研究人员基于BSP模型提出了新的处理方案,如Pregel,Hama,Giraph等.然而,图处理算法需要按照图的拓扑结构频繁交换中间计算结果而导致巨大的通信开销,这严重地影响了基于BSP模型的系统的处理性能.首先从降低消息通信的角度分析当前主流BSP系统的处理方案,然后提出了一种基于边聚簇的垂直混合划分策略(EC-VHP),并建立代价收益模型分析其消息通信优化的效果.在EC-VHP的基础上,提出了一个点-边计算模型,并设计了简单Hash索引和多队列并行顺序索引机制,进一步提高消息通信的处理效率.最后,在真实数据集和模拟数据集上的大量实验,验证了EC-VHP策略和索引机制的正确性和有效性. 相似文献
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基于多线程并行的大规模场景交互漫游研究 总被引:1,自引:0,他引:1
针对大规模三维场景的交互漫游,提出了一种基于多线程并行调度解决方案,并给出了相应的交互漫游算法.该方法使用离散层次细节技术结合视点相关的动态连续层次细节选择和过渡的批LOD技术.在预处理阶段,对大规模场景进行分层分块处理;在实时漫游阶段,采用多线程并行技术:绘制线程利用四又树层次进行可见性剔除和视点相关简化获取当前可绘地形,并将其提交给GPU进行绘制.预取线程通过预测视点的位置,从外存预取相关的几何数据并调入内存.将该方法应用于具体实例,取得了良好效果,证明了该并行方法的有效性. 相似文献
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大型网格模型多分辨率的外存构建与交互绘制 总被引:3,自引:1,他引:2
结合多分辨率、网格排布和基于视点的绘制技术,提出一种外存多分辨率构建和绘制算法.采用适应性八叉树对模型的包围盒进行划分,自顶向下构建模型的多分辨率层次结构,较好地保持了原模型的细节分布;并对多分辨率结构中每个节点所包含的三角形片段进行网格排布优化,降低了缓存的平均失效率;在实时绘制时,采用基于视点的细节层次选择策略进行模型的细化;最后通过引入数据预取机制来隐藏磁盘I/O延时,进一步提高绘制性能.实验结果表明,该算法在绘制速度与细节保留上均优于同类MRMM算法. 相似文献
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针对数字水印抗突发错误弱鲁棒性的特点,研究了SP(successive packing)二维交织算法,并根据RS纠错码的特性提出一种改进后的二维块交织BSP(block successive packing)算法。首先构造出低阶的SP交织矩阵,然后根据RS码每个码字分量的长度构造出单位块矩阵,将单位块矩阵按照低阶SP交织矩阵内元素的顺序排列构造出BSP交织矩阵。BSP交织矩阵能将多比特的RS码字分量分散开来提升其纠错能力。实验表明,BSP二维交织与RS纠错码相结合在二维空间上的抗突发错误的能力要优于相同码率的BCH码加SP二维交织,将其应用于水印系统能明显提升水印抗剪切攻击的鲁棒性。 相似文献
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线性四叉树在基于LoD的地表模型绘制中的应用 总被引:3,自引:2,他引:3
文章围绕三维可视化技术中的地表模型加速绘制方法进行了分析与探讨,针对传统绘制方法中所存在的不足之处,提出了一种新的基于线性四叉树的接边处理方法。其主要思想是:在基于LoD技术的地表细节层次模型的绘制方法的基础上,结合线性四叉树在邻域搜索上的特性,就能消除绘制中易出现的“裂痕”现象。 相似文献
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多细节层次描述(简称LoD)是实时绘制复杂几何场景的一种有效工具。基于层次结构的动态简化方法能够根据视点的变化,实时连续地转换场景细节模型。本文提出了一种改进的动态网格简化框架,它利用顶点映射机制支持不同细节层次之间的快速连续转换,同时还给出了建立和维护复杂场景动态简化层次结构的方法。 相似文献
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L.T. Waser E. Baltsavias K. Ecker H. Eisenbeiss E. Feldmeyer-Christe C. Ginzler M. Küchler L. Zhang 《Remote sensing of environment》2008,112(5):1956-1968
This paper presents an approach to assess increase and decrease (2002–1997) of forest area and other wooded areas in a mire biotope in the Pre-alpine zone of Central Switzerland using logistic regression models and airborne remote sensing data (CIR aerial images, DSM derived from them). The present study was carried out in the framework of the Swiss Mire Protection Program, where increase and decrease of forest areas are key issues. In a first step, automatic DSMs were generated using an image matching approach from CIR aerial images of 1997 and 2002. In a second step, the DSMs were co-registered and normalized using LiDAR data. Tree layers from both years of various levels of detail were then generated combining canopy covers derived from normalized DSMs with a multi-resolution segmentation and a fuzzy classification. On the basis of these tree layers, fractional tree/shrub covers were calculated using explanatory variables derived from these DSMs only. Bias was estimated by analysing the distribution of the fractional model differences. The corrected models reveal a decrease of tree/shrub probability which indicates a decrease of forest and other wooded areas between 1997 and 2002. The models also indicate real shrub encroachment in open mire. The detection of shrub encroachment may be helpful for selective logging purposes for sustainable mire habitat management. The study stresses the importance of high-resolution and high-quality DSMs and highlights the potential of fractional covers for ecological modeling. 相似文献
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Annotation support in interactive systems is often considered a simple task by the CG community, since it entails the apparently easy selection of a region and its connection with some information. The reality appears more complex. The scope of this paper is two-fold: first, to review the status of this domain, discussing and characterizing several approaches proposed in literature to manage annotations over geometric models; second, to present in detail an innovative solution proposed and assessed in the framework of Cultural Heritage (CH) applications, called ClippingVolumes. At the annotation definition stage ClippingVolumes uses 3D data to characterize the annotation region; subsequently, annotations are visualized by adopting a two-pass rendering solution which uses stencil buffers, thus without introducing new geometric elements, changing the topology or duplicating geometry elements. It solves most of the issues that afflict the current state of the art, such as fragmentation, annotation transfer to multiple representations and multi-resolution data encoding. The latter is a mandatory requirement to produce efficient web-based systems. We implemented and we fully tested this approach in the framework of a complex system that supports the documentation of CH restoration projects. 相似文献
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An efficient multi-resolution framework for high quality interactive rendering of massive point clouds using multi-way kd-trees 总被引:1,自引:0,他引:1
Prashant Goswami Fatih Erol Rahul Mukhi Renato Pajarola Enrico Gobbetti 《The Visual computer》2013,29(1):69-83
We present an efficient technique for out-of-core multi-resolution construction and high quality interactive visualization of massive point clouds. Our approach introduces a novel hierarchical level of detail (LOD) organization based on multi-way kd-trees, which simplifies memory management and allows control over the LOD-tree height. The LOD tree, constructed bottom up using a fast high-quality point simplification method, is fully balanced and contains all uniformly sized nodes. To this end, we introduce and analyze three efficient point simplification approaches that yield a desired number of high-quality output points. For constant rendering performance, we propose an efficient rendering-on-a-budget method with asynchronous data loading, which delivers fully continuous high quality rendering through LOD geo-morphing and deferred blending. Our algorithm is incorporated in a full end-to-end rendering system, which supports both local rendering and cluster-parallel distributed rendering. The method is evaluated on complex models made of hundreds of millions of point samples. 相似文献
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基于特征的CAD/CAE集成中并行建模技术研究* 总被引:1,自引:1,他引:0
为了解决传统CAD/CAE集成系统对同一产品串行生成不同的全细节层次模型和抽象模型的低效性与不实用性,采用基于特征的多分辨率建模技术和LOD技术,通过建立和查询存储在公共特征库中的多分辨率特征及LOD/LOA模型链表,实现自定义层次模型的并行快速同步提取和修改。实际应用表明,该方法能快速求得基于不同细节层次和抽象层次的简化模型,提高了实体模型设计与分析的效率。 相似文献