【作者】 张芹；

【导师】 吴慧中； 刘怡昕；

【作者基本信息】 南京理工大学 ， 计算机应用， 2002， 博士

【摘要】 用计算机生成真实感图形是计算机图形学中最具有挑战性的研究方向之一，本文在认真分析和总结前人相关工作的基础上，结合“三维实时图象生成和显示技术”课题的需求和应用，从图形模拟的角度出发，以真实感和实时性为目标，重点针对虚拟战场中特殊效果的处理需要，系统地研究了不规则模糊运动物体的建模理论及实现技术。论文所做主要工作和研究成果如下： 1．在分析研究和对比研究的基础上，对现有的不规则物体建模理论、算法及其应用范围进行了详细的分析和论述。 2．深入研究了描述模糊物体的粒子系统理论，探讨了其中存在的问题和局限性，通过对粒子系统中粒子数量和实时性关系的研究，提出了基于相似关系的结构粒子概念，提出了一种基于结构粒子相似关系属性的分割算法，能够自动简化粒子系统的模型，减少粒子系统的计算时间，并同时获得不同分辨率的层次细节模型，丰富和完善了粒子系统的理论，增强了粒子系统的描述能力。 3．针对虚拟战场中的特殊需求，研究了火焰效应的建模理论，引入了火苗粒子，建立了基于结构化粒子系统的火焰模型，从而大大减少了粒子系统中粒子的数量，提高了实时性。通过研究风力对火焰的影响，考虑了火焰受风力影响而产生紊乱的运动，利用小概率随机变化的粒子行为表现风力的作用，建立了风场中火焰的运动模型，并研究了虚拟战场中实际应用对火焰效果的多种要求，提出了参数化的战场火焰粒子系统模型，并给出了生成的算法，从而满是了其在形态、规模以及效果上多样性的要求，增加了火焰效果的真实感。 4．考虑到虚拟场景实时显示的需要，研究了粒子系统的快速显示算法，对每个特殊效应建立了不同细节层次的多级粒子系统。对于远景或较小规模的景象使用了细节低、粒子数少、渲染程度简单的粒子系统以加快显示速度，而对近景或较大规模的景象则使用了细节高、粒子数多、渲染程度复杂的粒子系统以增强显示效果。 5．系统地阐述了分形理论，并针对虚拟战场中特殊效果处理的需要，深入研究了爆炸现象的特征及变化过程，提出了基于迭代函数的爆炸烟雾造型方法，建立了爆炸烟雾的等熵运动模型，再现了烟雾景象。 6．通过对不规则模糊运动物体的研究，提出了一种比粒子系统更有广泛表达能力的分形粒子的建模理论及算法，为具有运动特征的模糊景物的模拟提供了又一途径，文中利用该法实现了云、火焰及爆炸烟雾变化的过程。更多还原

【Abstract】 Generating a visually convincing image especially for those irregular fuzzy objects is one of the most challenging and difficult problems in computer graphics. For generating and rendering the realism and the real-time image of irregular fuzzy object in the virtual battlefield ,which is needed in "Real-time Image Generation and Displaying Technology for Simulation", the theory and algorithms of modeling and simulating irregular fuzzy objects are researched in this paper.The exiting model of irregular objects such as procedural texture-based model, fractal-based model, cellular automata-based model and particle system-based model are discussed. After comparing their theories and algorithms, their application area are given.This paper goes deeply into the basic theory of particle system. Based on similar relation of particles, the concept of similar particle is proposed, and a approach for subdivision is presented ,which can automatically simplify the dynamics computation of particle systems and improve simulation speeds.A parameterized fire model considering wind effects and the multiformity of virtual battlefield based on structured particle systems and the corresponding realization algorithm is presented to give convincing model of fire to satisfy the need of virtual battlefield.For the need of real-time , quickly rendering algorithm is studied. By using lower level detail, fewer particle number and simple particle for far scene and small scene, the rendering speed is improved. On the other hand ,using higher level detail, larger particle number and complicated particle to generate more clear near scene and large scene.hi order to satisfy the need of special effects for virtual battlefield, fractal theory is discussed in detail. After analyzing explosion phenomena and its changing procedure, a new model of isentropic explosive gas based on fractal method is proposed. In this model, iterated function system(IFS) and the isentropic expansion rule were introduced to describe its characteristics. Also the definition of explosive gas and the corresponding realization algorithm is given to show explosive gas.At last, a new fractal particle method of modeling for irregular fuzzy moving objets is presented, also its realization algorithm and corresponding results of real-time rendering are given. Specially, fractal particle based on iteration function system is introduced. By this approach, we can reduced the number of particles greatly. Moreover, we can achieve realistic dynamic images such as cloud, flame and explosion which have naturally fractal appearances.更多还原