基于GPU粒子系统的战场实时雨雪效果模拟

雨雪效果的模拟可大幅提高战场视景仿真的真实感,粒子系统作为模拟不规则自然现象的有力工具,很适合雨雪效果的模拟,传统基于中央处理器(CPU)运算的粒子系统,模拟雨雪效果时存在占用大量CPU时间和系统资源的缺点,针对这个问题,建立了基于图形处理器(GPU)粒子系统的雨雪效果模拟方法,讨论了雨雪粒子系统在GPU上的实现、存储及运算等问题,通过将粒子系统的存储和运算全部交由GPU来完成,充分利用了GPU强大的处理能力和带宽优势,大幅提高了可模拟的雨雪粒子数量,并使雨雪模拟的逼真度和实时性都得到了增强.     

Microstructural resistance of snow following first wetting

One of the main causes for the formation of wet snow avalanches is the decrease in strength following the introduction of liquid water. The influence of liquid water on initially dry snow was investigated in twelve field experiments in the Eastern Swiss Alps. For this, a variety of different snow types were artificially wetted and liquid water content (using the Snow Fork), microstructural penetration resistance (Snow Micro Penetrometer, SMP) and snow density were measured. Measurements were repeated up to eight times resulting in a total 1100 liquid water content, 355 penetration resistance, and 737 snow density measurements. Following wetting, microstructural penetration resistance decreased in layers consisting of faceted crystals or depth hoar at low liquid water content. Layers consisting of precipitation particles or small round grains, on the other hand, showed no significant trend at a similar water content. The results indicate that first wetting of faceted crystals and depth hoar layers has an impact on snow strength, and consequently contributes to a decrease in snow stability.     

风雪耦合作用下单层柱面网壳的动力稳定

强风带动积雪漂移可能使结构处于稳定最不利状态,而目前在这方面的研究很少。该文研究一单层柱面网壳在风雪耦合作用下的动力稳定性。首先阐述风雪耦合作用下动力稳定性的研究方法,然后介绍风雪耦合作用的数值模拟,并通过风洞试验获得网壳表面的非定常气动力,最后分析了风雪耦合作用下单层柱面网壳的动力稳定。研究表明,斜风作用和不均匀分布...     

基于OSG粒子系统的雪景模拟

为了模拟真实降雪场景,建立逼真的雪景仿真系统,提出了一种基于OSG (open scene graph)粒子系统的仿真模拟技术,建立以雪粒子受力情况分析为核心的自定义雪粒子模型.该模型分析了雪粒子的具体受力情况,随机确定雪粒子的各初始属性,并在每帧中动态的赋予雪粒子不同的风力值以模拟真实降雪场景中的风力情况,解决了传统模型中雪粒子受力不够真实的情况.实验结果表明,自定义雪粒子模型能够更加真实的模拟降雪场景,具有逼真的仿真效果.     

基于GIS的中国西部SMMR积雪资料的评价*

用GIS方法对中国西部的SMMR微波积雪资料进行了初步评价。结果表明:SMMR资料的偏差程度因区域而异,在高海拔的高原区和高山区分别是8cm和6cm;低山区和盆地区无需偏差;而低海拔的丘陵区却需要4 cm的偏差。调整后的SMMR资料的区域差异不仅与高程有关,而且还与土壤、植被、坡面等地表特征有关。     

互联网时代背景下吉林红色文化融入冰雪旅游发展策略

互联网的快速发展为吉林红色文化的开发创造了良好的条件,吉林省又是冰雪旅游的重要区域,冰雪旅游已成为吉林旅游业的排头兵,在这种情况下应将吉林红色文化融入冰雪旅游发展中,在两者深入结合的情况,弘扬红色文化,推动冰雪旅游发展。本文根据现有研究资料,结合自身在冰雪旅游发展中的一些经验,针对吉林红色文化融入冰雪旅游发展战略进行分析,提出以抗联英雄和东北抗联烽火道为核心的红色文化融入冰雪旅游的方案,提出吉林省旅游管理部门应与党建管理部门等共同制订红色文化融入冰雪旅游的方案,在此基础上打造多个主题旅游项目,实现红色文化与旅游业发展的深度融合。     

大尺度三维复杂场景中雪动态模拟的方法

在大尺度三维复杂场景中,提出了降雪和积雪快速模拟的方法,采用视景体相关和线性分组变换的方法更新雪粒子系统,改进了降雪绘制的视觉效果。针对场景尺度大、复杂度高的特点,创建视点相关遮挡图（Occlusion Map）来精细绘制近处实体的表面积雪细节,生成积雪灰度纹理图来近似模拟远处地物的整体积雪效果,实现了大场景多细节层次积雪的动态模拟。在积雪绘制过程中,近处积雪细节模拟所需的视景体参数和遮挡图通过CPU获取,将复杂的积雪位置的判定和积雪量的计算从CPU移到GPU中,利用自定义的GPU顶点和片段操作加快了积雪模拟的速度。实验结果表明,在大尺度三维复杂场景交互式操作下,提出的方法能较好地实现雪的绘制和模拟。     

AMSR-E积雪产品在内蒙地区的精度验证

使用地面积雪观测数据对2005年～2008年40°N～48°N、112°E～128°E区域的AMSR-E积雪产品进行了误差分析和精度验证,结果表明:2005年～2008年的AMSR-E积雪产品较好地反映了研究区域地面积雪信息的时间变化特征;AMSR-E积雪产品普遍地低估了地面积雪深度,相对而言,当地面积雪较薄时,AMSR-E可较好地反映积雪深度,当积雪较厚时,AMSR-E明显低估积雪深度;2005年～2006年、2006年～2007年以及2007年～2008年3个冬-春季时段AMSR-E和站点观测值的平均差值分别达7.38cm,6.87cm和22.07cm。     

A Progressive Algorithm for Three Point Transport

When computing global illumination in environments made up of surfaces with general Bidirectional Reflection Distribution Functions, a three point formulation of the rendering equation can be used. Brute-force algorithms can lead to a linear system of equations whose matrix is cubic, which is expensive in time and space. The hierarchical approach is more efficient. Aupperle et al . proposed a hierarchical three point algorithm to compute global illumination in the presence of glossy reflection. We present in this paper some improvements we brought to this method: shooting, "lazy" push-pull, photometric subdivision criterion, etc. Then we will show how our new method takes into account non-planar surfaces in the hierarchical resolution process.     

A 2-dimensional multi rigid bodies skiing model

This paper develops a 2-dimensional model to simulate skiing movements based on multibody system. The model includes one rigid ski and five rigid skier’s segments (arms, trunk, thighs, shanks, and boots). The ski is modeled as a discrete-point rigid body. A spring-damper element is used to describe the interaction of every point between the ski and snow. The snow ground can be planar or uneven terrains. The air resistance of skier and ski are considered. Finally, several simple skiing movements were simulated. On the one hand, these simulations included some general skiing characteristics such as downhill, rotation, flying, and landing. On the other hand, the snow surfaces could be planar slope, sinusoidal slope, and rampant slope. The results show that the model can simulate simple types of skiing, and can provide kinematic and kinetic data such as the skier’s displacement, velocity, acceleration, joint moment and force, and ground reaction force. The model may be useful for building 3-dimensional skiing model, and for further studies of skiing movements.