四叉树结构地形网格简化算法的研究

对基于四叉树的层次细化模型生成地形网格的算法进行了研究。首先,对基于视相关的节点评价函数进行改进,提出利用加权距离和的方法判断地形节点距离视线的远近,以此引入视线因素对评价函数的影响,使得视相关的评价标准更加精确;其次,对层次细化中裂缝的产生及修补进行了分析,给出了裂缝修补的具体步骤,实现了LOD模型的无缝连接。实验结果表明,此算法保证了地形场景的显示质量,简化了地形网格的构造,提高了表面的渲染速度。     

一种基于LOD技术的场地渲染方法

为了解决游戏引擎设计中渲染效率的问题,提出了一种基于LOD技术的场地渲染方法。首先确定正方形的渲染地形,并利用四叉树分割渲染该地形,然后更新遍历渲染地形,最后进行龟裂的修补。各步骤依次使用节点分割与简化,节点剔除,地形龟裂处理等主要技术进行实现。实验结果表明,使用LOD技术后大型场景的渲染效果在效率及效果上均有较大提升,从而有效地提高了游戏的运行速度。     

基于粒子系统实现船舶航迹仿真的加速方法

为解决大规模粒子系统的实时性问题,提出一种基于LOD技术和硬件加速技术的混合加速技术.根据视点与景物间的距离建立粒子系统的LOD模型,并将该模型融入基于GPU的渲染流程中.整个实现流程采用FBO技术,通过两遍渲染方式完成粒子系统的绘制.虚拟海洋场景的船舶航迹实时试验表明,该方法可显著提高粒子系统的运算效率和绘制速度,与未采用任何加速策略而单纯基于CPU的绘制方法相比,其绘制效率提高近12倍.     

视景仿真系统中三维地形的实时生成方法

三维地形是虚拟自然环境中不可缺少的因素,也是虚拟仿真领域中视景系统的重要组成部分.三维地形的巨大数据量一直是视景仿真研究中的难点与热点.本文提出用函数曲面来保存地形顶点数据,在渲染开始前预先载入和计算生成地形数据,而在渲染阶段则利用视点相关LOD(Level of Detail)模型来简化渲染数据,实现大规模地形网格的绘制.实验结果表明,该方法能有效减少实时绘制时的计算量,提高绘制速度,较好地保证了大规模三维地形的实时生成效果.     

一种基于视点的大规模地形生成算法

采用视点相关的LOD技术提出一种简洁有效的方法，实现大规模地形场景的实时显示；把视野区域分为两种：基于地面车辆的视野区域和基于飞行器的视野区域，并提出相应的算法，达到地形实时显示速度与地形大小无关、算法中还提供了对视野区内背对观察者的场景进行剔除的方法和一种有效的网格评价算法、计算表明，该算法可以有效减少网格，提高场景显示速率．     

基于地形的自适应压缩和实时可视化

提出了一种具有高压缩比的海量地形自适应压缩算法,此算法基于地形变化的特征将整数小波变换和限制四叉树三角化方法相结合。高效的计算速度和多分辨率分析的优良特性使得它能够在任何视点下有效地降低小波系数,并且能使用快速更新策略对地形进行实时渲染,小波系数表明了多分辨率的地形变化。模拟结果表明此算法能有效压缩数据,实时连续地渲染海量地形。     

基于四叉树LOD技术绘制大地形的改进算法

分析基于四叉树的多分辨率网格简化技术LOD（Level Of Detail）的优缺点,在Lindstrom的基于定点化简准则的基础上,提出基于四叉树的LOD模型改进方法,即用最小二乘法估计地形精细度,用时间连续性方法处理视觉突起,用空间连续性方法处理T型裂缝。实验表明,改进的算法在一定程度上提高了地形漫游的运行效率并实现视点移动时地形绘制的平滑过渡。     

一种基于数据分块的海量地形快速漫游方法

大范围、海量地形数据的快速漫游是GIS、虚拟现实、游戏、仿真等领域的关键技术与难点之一。在目前地形数据简化算法的基础上,结合计算机硬件技术的发展,采用基于数据分块、部分数据常驻内存以及与视点相关的静态LOD模型实现了对任意格网大小海量地形数据的快速漫游。基于块节点的视景体裁剪、三角形条带组织以及边界裂缝消除、视觉光滑处理等手段的运用,提高了地形漫游的效率与可视化效果。     

基于着色器的LOD纹理混合与反走样平滑过渡关键技术研究

针对场景切换时产生的LOD(level of detail)纹理突变和走样问题,提出一种基于着色器的LOD纹理混合与反走样平滑过渡算法.该算法根据三维模型和视点的距离,运用基于Alpha测试的不透明蒙版算法和加权邻帧反走样算法,在LOD间生成过渡材质,实现三维模型LOD切换的平滑过渡,不仅能够改善纹理质量,而且能够保证...     

生成地形细节层次的粗糙度误差判据

误差判据是生成地形表面细节层次的核心问题,影响着三角形数目和地形三角形网的偏差.在分析各种误差判据计算结果的基础上,提出基于粗糙度的误差计算方法.采用表征地形起伏形状的粗糙度作为因子,建立误差评价函数,结合视点位置形成误差判据球,最后根据误差判据球生成地形细节层次模型.对误差判据改进后,适用于高空俯视地形及动态地形的细节层次技术(LOD)生成.试验表明,改进的粗糙度误差判据降低了地形网格中的三角形数量,对平坦地形的优化效率较突出.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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