【作者】 李蔚清；

【导师】 吴慧中；

【作者基本信息】 南京理工大学 ， 计算机应用， 2007， 博士

【摘要】 虚拟环境是VR系统的重要组成部分，对虚拟环境的研究是虚拟现实最重要的研究领域之一。分布式仿真技术与虚拟现实技术结合，对复杂仿真系统中的虚拟环境生成技术提出了较高的要求。本文围绕分布式仿真系统中的虚拟环境，对其理论和关键技术进行了深入研究与讨论。论文重点研究了场景绘制加速算法、多分辨率层次细节建模、分布式仿真支撑工具、基于硬件的加速绘制、开发和应用集成框架等，在研究虚拟环境生成技术的基础上，将其关键技术应用到虚拟环境的构建中，结合复杂电磁环境仿真和电力系统仿真等具体应用，扩展和验证了相关的理论和算法。论文主要研究工作包括：系统介绍了大规模真实感场景快速绘制的相关技术，提出了基于空间和运动特性约束的场景组织方法，采用可见性计算技术进行复杂场景加速绘制，基于场景的树型结构分别设计了静态场景的可见性预计算和动态场景的可见性修正算法；在研究边折叠模型简化算法的基础上，提出了一种具有特征参数约束的边折叠算法，给出了一种针对动态模型的基于梯度场的渐进网格和层次细节模型过渡区生成算法；深入研究了基于图形硬件的加速绘制方法。针对大型分布式仿真系统中虚拟环境开发的复杂性和日益迫切的应用需求，跟踪场景绘制、图形硬件、分布式仿真和软件设计模式的新进展，设计了基于OpenSceneGraph的三维场景渲染引擎和基于CERTI的分布仿真支撑工具，实现了一个分布式可扩展的虚拟环境开发框架。利用该开发框架，研究了动态数据的时空一致性问题，设计了分布式仿真系统中的动态环境时空一致性的实现机制。利用GPU作为快速计算工具，在电磁环境仿真方面，研究了基于抛物方程的雷达探测范围模型，基于几何光学碰撞检测算法提出了一种地形遮蔽盲区的快速算法，实现了复杂地形条件下的雷达盲区快速计算；在雷达组网条件下的复杂电磁环境仿真方面，研究了复杂模型快速体素化方法，设计了基于空间四叉树结构的表面体素高分辨率GPU切片法和具有几何约束的内部体素化方法，实现了多部雷达探测区和警戒区的快速计算，为雷达组网决策提供了可视化仿真工具；在复杂目标电磁散射特性估算方面，研究了图形电磁计算原理，采用光线追踪算法进行多次散射计算，设计了一个复杂目标电磁散射快速算法，实现了多次散射的快速计算。面向电力系统反事故仿真，基于分布仿真的高层体系结构，采样公共信息模型作为互操作接口；以HLA／RTI为基础实现组件通信机制；提出了一种电网等值计算方法，实现了地区电网实时联合仿真。在变电站仿真方面，设计实现了一个开放架构的变电站虚拟环境，针对变电站虚拟环境，研究了虚拟环境的模型组织、层次细节模型生成、基于上下文的碰撞检测、基于统计模型的特效仿真、人机交互等关键技术，实现了一个沉浸式的变电站分布仿真虚拟环境。更多还原

【Abstract】 As an important part of virtual reality system, virtual environment is a focus in virtualreality field. Virtual reality integrates into distributed simulation, and the complex virtualenvironment rendering becomes the key point. This dissertation concentrates on the keytheory and technology of virtual environment for distributed simulation system.This dissertation researches the accelerate of complex rendering, multi-resolutionLevel-of-Details modeling, distributed simulation Run-Time Infrastructure, rendering onGPUs, framework for developing and integration, etc. Build a framework of VR based onthe research of key technology of virtual environment rendering. The virtual environmenttheory and algorithm are applied to the application of complex electromagnetic virtualenvironment and the power system simulation. Generally, the main research points in thispaper are as follows:This dissertation introduces the acceleration of rendering for large scale scene. Basedon the space and motion relation, the scene is constructed into a hierarchical tree. A fastvisibility culling method is proposed to accelerate rendering, according to static visibilityculling and dynamic culling correction. According to the research of edge-collapsesimplification of complex model, a new algorithm of LOD models generation is proposedwhich is concern not only geometry properties but also features. To handle the dynamicenvironments in VR, an algorithm based on the extension of resolution is improved usinggrads in the terrain’s data to generate progressive meshes.To ease the complexity of virtual environment for distributed simulation and to meetthe requirements of system development, some new technologies such as rendering, GPUs,distribute simulation and design patterns are concerned. A virtual environmentdevelopment framework is designed, using OpenSceneGraph as a rendering engine andCERTI as a HLA component, to archive the flexibility and expansibility. Based on thisframework, the technology of time-space consistent in distributed system is studied, and amethod to satisfied time-space consistent is proposed.In complex electromagnetic virtual environment, GPU is used as a fast simulation tool.A new algorithm for estimation of radar shadow affected by 3D terrain is proposed basedon parabolic equation theory and collision detection method. The shadow zone of radar canbe simulated is real-time. In the situation of radar netting, a voxelization method isproposed to calculatingthe guarding zone and detecting zone. A high resolution GPU clipping method based on quad-tree is used to voxelize the surface. Ray intersectionmethod is adapted to filling the inner space. A fast intersection algorithm is used tosimulate radar netting, based on the voxelization result. The algorithm for radar nettingsimulation is fast, which could provide scientific visualization and decision supporting. Anew Graphical Electromagnetic Computing (GRECO) method for RCS of complex objectsis proposed based on ray-tracing and Physical Optics(PO) theory under multi-scattering.All these algorithms are realized on GPUs to use the ability of graphic hardware.In emergency simulation of power system, a prototype system has been built based onHLA to achieved interoperability and consistency. This system using some key technologysuch as interoperability based on CIM, communication based on HLA/RTI component andthe equivalence simulation of peer power systems. This system is suited for large scaleemergency power simulation. In virtual environment of substation simulator, thearchitecture of transformer substation’s virtual environment is studied. A method oforganizing the virtual space and objects’ models into a hierarchy tree according to theirelectric relationship was applied. Given an accelerated algorithm of collision detection,which is context-sensitive. Particle system is used to simulate the effects of dielectricbreakdown, rain and snow falling. This immersive virtual environment is successfullyrealized for substation training simulator.更多还原