【作者】 王长波；

【导师】 彭群生； 王章野；

【作者基本信息】 浙江大学 ， 应用数学， 2006， 博士

【摘要】 真实感自然景物的实时建模与绘制一直是计算机图形学研究的热点和难点之一，它在计算机动画、电脑游戏、影视特技、军事仿真、建筑景观设计、虚拟现实等领域都有非常广泛的应用。值得注意的是各类自然景物如树木、花草、雨雪、云、烟雾、火焰等的模拟至今尚无统一的方法。随着计算机图形学的发展和应用需求的不断扩大，人们已不再仅仅满足于表现自然景物的静态真实感效果，而更希望模拟它们在自然场景中的动态变化过程。为此，一方面必须引入自然景观形成的物理模型，在视觉上达到更逼真的效果；另一方面，还需对上述物理模型进行适当简化，以实现快速绘制。 本文第一章介绍了自然景物的研究意义和研究难点，综述了已有自然景物建模和绘制方法，分析了它们各自的优缺点，指出基于物理的自然景物的真实感动态绘制是当前的主要研究方向之一，提出了本文的主要研究内容，包括：考虑折射的天空场景真实感模拟，飘雪场景的实时绘制，风吹草动的动态建模与绘制，海市蜃楼场景的实时模拟，下雨场景的实时建模与绘制。 本文第二章提出了一种新的考虑大气折射的天空光模型来绘制天空场景。传统的天空场景绘制方法大都基于大气对天空光和太阳光的散射，而未能考虑大气折射的影响，因此无法绘制出太阳和月亮场景在不同观测条件下形状、色泽、光晕的变化。本文提出了一种考虑大气折射的天空光模型，首先基于大气光学知识推导出大气折射率与气压、温度和水汽压的定量关系，详细计算了光线在大气中的折射轨迹，采用一种考虑折射的路径跟踪方法计算天空光强度的分布，并绘制出不同时间、不同季节、不同观测地点下更具真实感的太阳、月亮和星星的天空场景。 通过风场建模和引入风雪交互作用机制，本文第三章首次实时绘制出逼真的飘雪动态场景。由于复杂风场的建模和实时求解十分困难，本文提出了一种基于离散Boltzmann方程的新方法来快速模拟三维风场；根据风雪的交互作用机理，建立了雪的飘动、沉积、侵蚀等变化规则；采用一系列简化和加速绘制的方法，真实感地实时绘制出不同风速下不同降雪量的风雪场景。 本文第四章提出了一种大规模草地的动态建模与绘制方法。风吹草动的模拟不仅涉及到风与草的交互作用，也给草的几何造型提出了更高的要求，传统更多还原

【Abstract】 Real-time modeling and rendering of natural phenomena has been a hotspot and one of the most difficult tasks in Compute Graphics. It has been found wide application in many domains such as computer animation, landscaping, architecture, special effects of movie, computer games, battlefield simulation and virtual reality, etc. However, there is no an uniform method to render the nuture phenomena include trees, flows, grasses, clouds, snow, rain, fog, fire, etc. Recently for the simulation of natural phenomena, people more focus on the dynamic modeling and rendering based on the physics reality, and the whole results considering the interactive effects between the nature phenomena and the environment. So the physically based modeling must be applied to attain more realistic results on both shapes and movements, on the other hand, the simplification and acceleration techniques also should be introduced to realistic render the dynamic and whole effects of natural phenomena more quickly. It aims to seek for a tradeoff between the realistic effects and real time performance, to meet the needs from various applications.This paper introduces the research significance and difficulties of the simulation of nature phenomena in Chapter 1, then surveys these methods used in the simulation of natural phenomena, and analyses their advantage and applied limition. We point out that the physically based realistic dynamic rendering of natural phenomena will be the main developing trend in this field recently. In this paper, we focus on the realistic rendering of several typical natural phenomena, include: realistic rendering of sky scene considering atmospheric refaction, real-time simulation of wind-driven snowing scene, dynamic modeling and rendering of grass wagging in wind, real-time rendering of dynamic mirage scene, Real-time modeling and rendering of dynamic raining scene.In Chapter 2 of this paper, a new sky illumination model considering更多还原