【作者】 任鸿翔；

【导师】 金一丞；

【作者基本信息】 大连海事大学 ， 交通信息工程及控制， 2009， 博士

【摘要】 随着高性能微机的持续更新换代、GPU可编程能力的大幅度提高以及计算机图形技术的飞速发展,用户对航海模拟器的功能及虚拟环境提出了更高的要求。为了提高航海模拟器视景系统的实时性和真实感,本文对GPU技术、海浪真实感绘制算法、海上溢油三维可视化算法等进行了研究,所做的工作主要包括:1.基于GPU开发仿真系统中的三维场景已逐渐成为计算机图形学领域关注的热点。本文对GPU的关键技术、高级绘制语言进行了阐述,对GPU编程的优势、特点进行了分析,对GPU在计算机图形学领域中的应用进行了综述。2.科学、实时、逼真地绘制海浪对航海模拟器视景系统十分重要。本文在分析现有波浪理论的基础上,针对航海模拟器的实际需求,采用基于统计和谱的方法,利用GPU技术对海浪的绘制算法进行研究,提出了一套完整的大规模海浪场景真实感绘制算法。首先给出同心圆网格模型构建海浪表面,更合理地实现了LOD,保证了海浪绘制的实时性;采用基于GPU的FFT方法生成符合Phillips谱的海浪高度图;利用顶点纹理获取技术采样多次平铺的高度图,得到网格顶点的高度,用网格构建出了海浪的几何形状;而后模拟了Choppy波,减轻了磁砖效应,实现了海浪与船舶的相对运动;最后模拟了海面的反射效果、折射效果以及海浪中的浪花效果。3.海上溢油三维可视化尚未见比较好的实现方法。本文对海上溢油可视化的相关理论和技术进行了分析,在海浪真实感绘制算法的基础上,提出了实现海上溢油三维可视化的方法。首先将较短时间尺度内的点源瞬时溢油过程分为油膜自身扩展和油膜漂移扩散两个阶段,分别选取椭圆模型和油粒子模型计算各阶段的溢油轨迹;采用粒子系统方法实现油粒子模型;利用平面折射技术将轨迹模拟结果转化为溢油发展变化的纹理图,再在GPU的片元着色器中通过投影纹理坐标访问该纹理,从而模拟和再现了海上溢油的三维场景。4.场景数据库建模和管理的好坏直接关系到场景数据库的绘制效率。本文通过对场景数据库的树形层次结构及绘制过程的分析,提出了采用空间和逻辑相结合的结构组织数据库,同时对场景数据库中节点的尺寸和数量、LOD的结构、状态改变等技术做了详细讨论,这些技术有助于提高场景数据库的绘制效率。本文选用OSG作为航海模拟器视景系统的管理平台,对OSG的场景图进行了重点分析,并利用场景图的强大功能来管理和显示航海模拟器的场景。更多还原

【Abstract】 With the continuous updating of high performance computer,the great improvement of GPU programmability and the rapid development of the computer graphics technology,users have higher requirements on simulation function and it’s virtual operating environment of marine simulator.To improve the real-time capability and realism of visual system,the dissertation mainly studies GPU technology,realistic rendering of ocean wave and 3D visualization of marine oil spill.The mainly contributions of this dissertation are:1.Developing 3D visual system for simulation system based on GPU has gradually become a focus in computer graphics.In the dissertation,the key technologies and high-level rendering languages of GPU are discussed,the advantages and features of GPU program are analyzed,and the applications of GPU in computer graphics are reviewed.2.To render ocean wave scientifically,rapidly and realistically is an important aspect in marine simulator.According to the actual demand of marine simulator,the spectrum method is studied aider analyzing the wave theory.A new realistic scene rendering algorithm of large-scale ocean wave is proposed based on GPU.To guarantee the real-time capability of rendering,a grid of concentric circles is proposed to represent ocean surface.The fast Fourier transform based on GPU is used to generate the height map of ocean surface,the height of grid vertex can be obtained through sampling the tiled height map with the technology of vertex texture fetch,and the ocean wave geometry is modeled with the grid form.Then the choppy wave is simulated,the repeating tile of ocean is not apparent,and the relative motion between ocean and ship is achieved.Moreover,the reflection and refraction of ocean surface are added and the spray is simulated. 3.On the basis of the realistic rendering algorithm of ocean wave,a method of 3D visualization of marine oil spill is proposed after analyzing the related theory and technology.Firstly,the early process of instantaneous oil spill is divided into two phases:oil spread,oil drift and dispersion,and the track of each stage is calculated using the respective mathematical model.Then the particle system is adopted to implement the oil particle model.Using the technique of planar refraction map,the track of oil spill is generated to a texture which is projected to ocean surface in fragment shader.4.The modeling and manageing of scene database will directly affect the rendering efficiency of scene.The tree structure and the rendering process of scene database are analyzed.A structure combining logic and space is developed to organize the database. Several key technologies are discussed to improve the rendering efficiency of scene, including the number and size of node,the LOD structure,the state change,etc. Furthermore,the scene graph of OSG is emphatically analyzed,and the scene of marine simulator is managed and displayed with the powerful functions of OSG.更多还原