Study Of The Real-Time Rendering For Large-Scale Terrain Dataset

Visualization of terrain information is playing a key role in many applications such as flight simulation, 3D geographic information system, etc. However, with the rapid development of the remote sense and satellite technology, people expect to investigate or view larger terrain regions with finer precision, which inevitably leads to the real time visualization of huge terrain dataset.In this paper, we propose an efficient framework for large-scale terrain real-time visualization. Within this framework, the approach for integrating multiresolution representations of terrain geometry and terrain texture data is presented. Geometry data is modeled as a regular grid, and texture comes from the remote sense or satellite images. The multiresolution models for terrain texture data and geometry data are matched with each other: To achieve the goal of real time visualization, our framework selects geometry and texture patches based on the screen-space error criteria conforming to the current viewpoint. The most important feature of our framework is that its performance is almost independent to the scale of the input data scale regardless it is far beyond the internal memory.In Chapter 1, we investigate some backgrounds and application domains of the real-time rendering of large-scale terrain data set. And suggest some fundamental strategies for accelerating the rendering and image quality. Meanwhile, we summarize some resolutions which are presented in recent publications, and enumerate and discuss the research works about terrain rendering in recent years.In Chapter 2, we discuss the terrain modeling with continuous level of detail, and present a new error metric for dynamic terrain mesh simplification, this metric estimates more precisely the projected error in screen-space by introducing a tightly bounded surrounding cylinder associated with each vertex.The error metric can be stored and computed efficiently. We propose a novel time-critical optimization strategy to mesh refinement by further exploiting frame-to-frame coherence. To mitigate the visual "popping" during the detail level transit, we introduce a deferred merging method to realize the geomorphing in terrain mesh refinement. To further accelerate terrain rendering, our approach integrates view frustum culling, back face culling and triangle strips.In Chapter 3, for the case that the terrain data can not fit in memory, we describe a data layout technique of providing coherent access to the terrain data that are consistent with our mesh simplification. We reorder the data in a manner that is of multiresolution and the overhead is completely eliminated. The locality of the index is inherited from Sierpinski curve. Further we organize the data as multi layer and each layer data is of multiresolution. We combine caching and prefetching techniques to obtain further speed-ups.In Chapter 4, to increase the perceived realism of the terrain, we depict a new texture mapping approach to handle the tremendous texture data in real-time. The texture data are organized in a quadtree as a bandwidth-limited resource rather than a finite resource. Integrating with the continuous level of detail of geometry mesh, we present an criteria for selecting an appropriate node on the texture the quadtree, and rendering the mesh with the corresponding quadtree texture. Exploiting the frame coherence, the display of large scale texture is reduced to a caching problem in which texture memory serves as the primary cache for texture data, main memory the secondary cache, and local disk the tertiary cache. By using this cache hierarchy, applications are able to maintain real-time performance while displaying textures hundreds of times larger than that can fit into texture memory. For reducing the storage of texture data, we present an algorithm for texture compression based texture pyramid. Eecoding speed of our current approach is essential and it is proved to be efficient. Texture pyramid can be used for anti-aliasing.high-quality shading is often realize...