【作者】 王林旭；

【导师】 李思昆；

【作者基本信息】 中国人民解放军国防科学技术大学 ， 计算机科学与技术， 2002， 博士

【摘要】 虚拟战场以其在军事训练演习上特有的科学性、经济性、对抗性、直观性、交互性、实时性等诸多优点，为各国军队提供了在新时期下实现战略、战役、战术想定演练的有效途径，能大大提高军事作战模拟训练质量。虚拟战场需要有一个实时动态变化的、逼真的虚拟作战自然环境。特殊效果生成技术和实体模型简化技术是构建实时动态变化且逼真的虚拟作战自然环境的关键技术。 本文主要对虚拟战场中一些特殊效果的生成技术和实体模型的简化技术进行了深入的研究，所完成的主要研究工作和取得的主要研究成果如下： (1)动态地形的实时可视化技术 在虚拟战场中，需要真实地实时表现出炮弹在地面上炸出的弹坑以及车辆驶过地面后留下的清晰压痕。由于炮弹在地面上炸出弹坑和车辆驶过地面后留下压痕，其本质上都是改变了地形表面某处的高程值和(或)颜色纹理等属性，所以，本文将这两种特殊效果的实时生成技术统一为动态地形的实时可视化技术。地形表面的连续层次细节动态绘制技术，是构建虚拟作战自然环境的关键技术，也是生成弹坑和车辆驶过地面后留下的压痕等地表特殊效果的技术基础。 本文在定义了一种合理且有效的嵌套误差判据球的基础上，提出了一种快速的、视点相关的、连续层次细节地形表面绘制算法。本文定义的嵌套误差判据球可隐式地保证地表网格中裂缝的自动消除。该算法是实时生成各种动态地形效果的技术基础。实验结果证实了该算法的快速性和有效性。 本文在上述算法的基础上，针对动态地形可视化的特殊需求，提出了地表网格分辨率的动态扩展技术，研究并证明了需扩展其分辨率的最大区域，进而提出了动态地形的实时可视化方法。该方法既消除了地表网格模型中的不连续问题，义能很好的表现地形的形变效果。实验表明，本文方法是可行且有效的。本文方法不但可以实时生成逼真的弹坑、车辆压痕等特殊效果，而且可以表现如战壕等其他改变了地表高程值或颜色纹理属性的动态地形效果。 国防科学技术大学研究生院学位论文 (2)水中爆炸产生的水柱运动建模与实时绘制技术 在海战中，弹药在水中爆炸常会产生非常壮观的水柱。水柱是海战中常见的特殊效果现象。能否实时而逼真地模拟水柱的运动，将直接影响到虚拟海战环境的真实感。 本文提出了一种模拟弹药在水中爆炸而产生的水柱运动的方法。从分析水中爆炸的物理现象入手，建立了构成水柱的各水粒子的初始速度计算模型，结合水粒子的受力情况，给出了水粒子的运动方程。为满足实时性要求，使用垂直于当前视线的平面上的一小块圆形区域，结合纹理映射技术，对水粒子团进行造型。实验结果表明，该方法可同时满足实时性和逼真性的要求。 (3)爆炸冲击波对建筑物等几何实体的毁坏效果实时模拟技术 弹药爆炸产生的冲击波会对建筑物等造成严重的毁坏。形象的表现这种毁坏过程和结果，能增强虚拟战场的真实感。 本文提出了一种基于相互链接的五面体构造物体的三维实体模型的新方法。基于这样的三维实体模型，应用随机函数，可构造出各不相同的、具有不规则形状的三维立体碎块。为了满足实时性需求，本文使用最简单的冲击波—球形冲击波，并基一于球形冲击波的径向传播特性和随机函数求解各碎块的初始速度(包括速率和方向)，进而提出了实时模拟爆炸冲击波对砖石结构建筑物等毁坏过程(不涉及爆炸云)的解决方案。实验结果表明，该解决方案能逼真地表现砖石结构建筑物等的逐渐倒塌(逐渐破碎)过程、毁坏后的残垣断壁以及碎块在地面上的堆积效果，并能满足实时性要求。 (4)实体模型简化技术 虚拟战场场景中包含有大量的自然实体和作战实体，这些实体的原始几何模型常常是采样密集的三角形网格。为了满足虚拟战场中限时图形绘制的要求，必须事先对实体复杂的原始网格模型进行简化。 本文提出了一种新的基于三角形折叠的网格简化算法。该算法以三角形三个顶点到各自相关的平均平面的距离的最大值为权值，确定三角形的折叠顺序，并以几角形的加权一蓑心作为折叠点，而目_，给出了模型简化时颜色和纹理等表面属!I性的处理方法。该算法实现简单，速度快且能较好地保持原有网格的特征（包括几何特征和颜色、纹理等表面属性信息）。文中给出的一组实例说明了该算法的有效性。更多还原

【Abstract】 Virtual battlefield has many particular advantages in the military maneuver, such as scientific, economical, antagonistic, intuitional, interactive, real-time, etc. And it provides an efficient approach to implement the scenario of stratagem, battle and tactic for all the armies in the world in the new age, and enhances the training effect for the participants. It is necessary to the virtual battlefield that a virtual battle natural environment should be realistic and be updated dynamically in real time. The generating technique of special effects and surface simplification technique of object models are the key to build such a virtual battle natural environment.In this dissertation, we study the generating technique of special effects and surface simplification technique of object models in the virtual battlefield. The main research and contributions of this dissertation are:(1) Real-time visualization of dynamic terrainIn the virtual battlefield scene, it is necessary to display craters on the ground due to the explosion of cannonball and legible tire tracks behind a moving vehicle. Both craters and tire tracks change either the elevation of terrain or the surface properties such as color, texture. Therefore, we called the technique to generate the craters and the tire tracks in real time as the technique of real-time visualization of dynamic terrain. The rendering of continuous LOD terrain surface is the key technique to build the virtual battlefield scene, and it is also the technical basis of generating the special effects such as craters, tire tracks.In this dissertation, the definition of an appropriate and validnested error metric sphere is presented, and a fast continuous LOD terrain rendering algorithm is proposed. And the nested error metric can eliminates the cracks in the meshes of the terrain surface automatically and implicitly. This algorithm is the technical basis of generating the special effects on the ground. Examples illustrate speediness and efficiency of the algorithm.To meet the special requirement in visualization of dynamic terrain, a technology which is called dynamically extending the resolution of terrain surface meshes is proposed based on the aforesaid fast continuous LOD terrain rendering algorithm. A theorem on the maximal region which needs to extend its resolution is given and proved. And the complete solution to visualize the dynamic terrain in real time is given. It both eliminates mesh discontinuities and represents the deformed region well in terrain model. Based on the complete solution, many kinds of special effects on the ground such as the realistic craters, tire tracks and trench can be generated in real time. Examples in this dissertation illustrate practicability and efficiency of the solution.(2) Modeling and real-time rendering of water columns which are generated by an underwater explosionIn a naval battle, after the underwater detonating of high-condensed explosives, grand water columns usually will come into being on the sea surface. Simulating realistically water columns’ behavior in real time contributes greatly to the sense of reality of virtual naval battle environment.A method is proposed to simulate water columns’ behavior generated by an underwater explosion. The physical phenomena of underwater explosion are analyzed, and the initial velocity equations and dynamics equations of water particles, which compose the water columns, are setup. For real-time requirement, each water particles cluster is rendered as a small circular area in a plane that faces the viewer, and this small area is texture-mapped with a pre-captured image of water particles cluster, with an intensity-based alpha channel. Examples illustrate that the method can meet the requirements of real time and reality.(3) Real-time simulation of the building shattering caused by the blast waveThe blast wave that generated by an explosion can destroy the objects badly such as the buildings. Realistic simulation of the shattering of the objects can enhance更多还原