【作者】 王海玲；

【导师】 印桂生；

【作者基本信息】 哈尔滨工程大学 ， 计算机应用技术， 2013， 博士

【摘要】 随着虚拟现实技术应用的推广和普及，虚拟场景建模与绘制技术研究逐渐成为一个热门研究课题，并已被广泛应用于战场仿真、航空航天、自然风光展示、远程教育和训练培训等众多领域。近年来，由于人们对虚拟场景真实性需求的不断提升，虚拟场景仿真突现出模型建模复杂度、规模性与绘制速度之间的矛盾问题。在建模真实感和绘制实时性相平衡方面，建模与绘制技术研究仍存在着诸多挑战，因此，对虚拟自然场景建模与绘制技术的研究具有重要的理论意义和应用前景。本文重点围绕模型简化、大规模地形建模与绘制、动态海面波浪建模与绘制以及碰撞检测等关键技术进行分析和研究，具体内容如下：（1）模型简化是实时绘制的必要前提和重要手段，本文重点研究特征保持的模型简化技术。针对QSlim算法的过简化问题，提出区域划分和多特征引导的模型简化方法。首先在分析物体属性特征的基础上，对模型进行区域划分并计算其三角形单元的分布密度，以控制模型简化深度，然后利用模型的几何特征、视觉特征构造多特征度量函数，以增强简化模型的特征保持，使新方法在保证计算速度的同时也可有效保持简化模型的特征信息。（2）地形是虚拟自然场景仿真的基本组成部分，针对大规模地形的复杂度与绘制速度间的矛盾问题，提出大规模地形的数据组织与调度方法，即外存数据管理和内存多线程调度。在外存方面，将大规模地形进行分块，分别创建多分辨率层次，并结合顶点相关性进行数据排序和压缩；在内存方面，利用基于视点运动特性进行地形数据预取，并采用多线程并行策略进行数据调度，使该方法在保证地形真实感的基础上，减少数据调度量，从而提高地形绘制速度。（3）动态海面模拟是影响虚拟自然场景仿真质量的关键因素，针对动态海面模拟中的真实感和实时性间的矛盾问题，提出算法调和的动态海面建模方法。该方法将动态海面视作基波、高频细波和光照模型的调和产物，结合海浪谱参数和余弦波叠加构造基波模型，利用基于波浪动态特征修正的分形算法调和海面的高频细波，最后研究GPU调和的海面光照技术，使该方法在不影响动态海面视觉效果的前提下，可有效提高其绘制速度。（4）碰撞检测是虚拟场景仿真的“生命”体征之一，考虑碰撞检测算法的实时性需求，提出基于CPU和GPU的并行碰撞检测方法。在分析拓扑结构图的基础上，创建拓扑结构图引导的包围盒层次，并结合拓扑结构图同层节点间的分离性，提出CPU多线程并行策略更新和遍历包围盒及包围盒层次，此外，利用GPU并行计算三角形的相交性，并研究数据组织方法和通信策略以提高CPU与GPU间的通信效率，使该方法能有效减少包围盒相交测试对的数量，提高碰撞检测速度。更多还原

【Abstract】 With the virtual reality applications widely used in many fields, such as militarysimulation, aerospace, natural scenery display, distance education, virtual training and so on,modeling and rendering of virtual natural scene has been a hot research topic. To serve theraising demand of human for realism and real-time, more scene geometry becomes complex,even the most advanced rendering hardware cannot provide interactive rates. High-fidelitymodeling and real-time rendering for virtual natural scene play an important role in manyapplication fields. Therefore, the researches for modeling and rendering of virtual naturalscene have profound theoretical significance and broad application prospect. This papermainly focus on several key techniques, such as mesh simplification, fast terrain rendering,simulation of water waves dynamics and collision detection. The major contents aresummarized as follows:（1）Mesh simplification is a very important research in many domains, our primaryresearch is feature retained mesh simplification algrotithm. This paper present a novel meshsimplification algorithm based on area partition and multi-feature weighted. The proposedmethod consists of two phases: multi-feature weighted optimization and mesh simplification.First, building a hierarchical structure using area partition, then computing the meshmulti-feature saliency metric combining geometric featrue metric and visual featrue metric.Second, the mesh simplification is running with area partition and multi-feature saliencymetric, to get fast and effective siplified models. To evaluate the quality of our algorithm,many existing simplification algorithms are used to compare the quality and speed of meshsimplification.（2）Terrain rendering is a major factor in virtual natrual scene simulation. Interactiverendering of massive terrains still remains a challenging problem because of ever increasingterrain scale and complexity, even the current advanceed hardware design trend cannotprovide fast data access. Our primary point is accelerating terrain rendering with developingdata management techniques of out-of-core and many threads data scheduling in-core, such asview-point position, direction and motion vector of the viewpoin, to solve the above problem.The proposed method uses an off-line process to manage terrain data with techniques such as data block partition, multi-resolution, compression scheme with vertex correlation for everyterrain block. At runtime, the prepatching approach and multi-thread parallel data schedulingare used to reduce the cost of the data exchange and improve the efficienty of renderinglarge-scale terrain.（3）Dynamic ocean surface simulation is also a crucial topic in virtual natural scenesimulation that affects the realism of the applifications. An effective dynamic wave simulationapproach is proposed to solve the problems of realism and real-time. The dynamic wavemodel is divided into fundamental wave, high-frequency detail wave and optical effect. Firstof all, the fundamental wave is implemented by combining cosine wave superposition withocean wave spectrum. Secondly, the high-frequency detail wave is generated using the fractalalgorithm and wave feature analyzing, established a new parameter equation feature-based forfractal parameter optimization. Last but not least, the realistic effects with texture mappingand illumination model is achieved on the GPU.（4）Fast and effective collision detection algorithm is still hard to fulfill in computergraphics. To speedup collision detection, a novel parallel algorithm for collision detectionbased on CPU and GPU is proposed. Firstly, constructing bounding volume and boundingvolume hierarchy for models according to their topology graph to reduce the amount ofbounding volume intersection, and assigning the task of updating bounding volume andbounding volume hierarchy into many-core CPU to parallel computing, with nodeindependence of topology graph. Secondly, the triangles intersection is computing in manyprocessors of GPU, and using spatial Morton code to order geometric primitives as the linearordering to reduce throughput between CPU and GPU. Our algorithm has efficient speedup toconstruct hierarchies of models with up to several million triangles, and is fast for collisiondetection.更多还原