【作者】 罗景馨；

【导师】 唐琎；

【作者基本信息】 中南大学 ， 计算机应用技术， 2009， 硕士

【摘要】 三维场景漫游是指,用户通过某些设备,与屏幕上显示的真实或虚构的三维场景环境进行交互操作。这种操作能实现在虚拟环境里模拟人在真实场景中的漫游。场景漫游作为虚拟现实领域的一个重要方向,有着广阔的发展空间和应用前景。以全面了解虚拟现实及场景漫游的相关理论研究,着重分析这个方向上前人的优秀成果为基础,深入研究了三维场景漫游中涉及的几种关键技术,其中包括场景简化的LOD(Level of Detail)技术、漫游时的碰撞检测技术和自动漫游中的路径规划技术等。因虚拟场景的数据量大,从而导致机器的计算能力不能满足场景实时绘制的要求等问题,本文利用LOD技术对场景的实时显示进行优化。在基于规则网格模型的基础上,提出了一种对四叉树的分割和节点存储结构同时进行改进的LOD算法。它通过减少误差判断次数加快了四叉树的生成速度,同时改变传统的节点存储方式,降低了数据的冗余存储。另外,为了能尽量真实地模拟现实世界,在三维场景中漫游时,还需解决漫游中可能产生的碰撞问题。采用一种基于混合包围盒的碰撞检测算法,对大量明显不相交的对象进行快速排除,这在一定程度上减小了检测的复杂度。根据所用数据结构的特点,算法中用了插入排序的思想并对其进行了改进,以降低时间上的开销。最后,针对三维场景中的交互式漫游和自动路径漫游两种方式,在简单分析了交互式漫游的实现方法后,对自动漫游方式进行了仔细研究。根据所研究的三维场景漫游的特点,将三维障碍物以某种规则投影到二维平面后进行路径规划处理,并对前人基于三维空间的规划方法加以改进,成为适合本文三维场景的路径规划方法,同时对路径的合理性方面也做了处理。更多还原

【Abstract】 3D scene walkthrough means users can interact with real or virtual 3D scene environment which is indicated on the screen by some equipment. This operation can be used to simulate the man’s walkthrough in real environment. Scene walkthrough is very important in the field of VR, and has a broad horizonand bright prospect for development.In this thesis, by having a thorough knowledge of relative theory of VR and scene walkthrough, the former research is dissected in this direction and then several key techniqies involved in 3D scene walkthrough are studied in depth. These techniqies include LOD (Level of Detail) simplifying scene, collision detection when moving and path planning for automated walkthrough.Virtual environment always means a mass of data. Because of this problem, the computing-power of computers can not meet the needs of real-time rendering scene. In such cases the LOD is used to improve real-time scene display. On the basis of regular net model, a LOD algorithm based on improved quadtree-split and node storage is introduced. In order to expedite the speed of quadtree generation, the times of error judgment is dwindled down. And at the same time, a new node storage structure means much less redundant data can be stored than traditional way.And besides, in order to simulate the real world best, the problem of collision should be solved at the walkthrough time in 3D scene. A collision detection algorithm based on mixed hierarchical bounding volumes is proposed. And lots of objects which don’t collide with each other are excluded quickly. It reduces the complexity of detection to a certain extent. By the characteristic of data structure in this thesis, insertion sort is used and improved in the algorithm. It can reduce the consumptive of time.Finally, for interactive walkthrough and automated walkthrough these two ways in 3D scene, the implementation method of interactive walkthrough is analysed simply, and after that automated walkthrough is researched in detail. In accordance with the peculiarity of 3D scene walkthrough researched in this thesis, obstacles having three dimensions project some shadows on two-dimensional. Then path planning is implemented on two-dimensional. The method of predecessor basis on three dimensions is improved and used in this thesis. So it is suitable for the 3D scene discussed in this thesis. At the same time the ratio-nality of path also can be thought.更多还原