Reserch On LOD Technology And Its Application In Undersea Terrain Real-time Rendering

Exploitation of marine resources is an important way to solve the energy crisis. It is the primary means of marine energy finding. It is difficult to dive into the seabed because of natural conditions. We need to understand ocean through observing the simulative submarine topography. The main purpose of this project is to study the seabed terrain rendering progress at home and abroad, to analyze the pros and cons of different ways, to obtain feasible solutions, to optimize programs on this basis, at last, to improve the rendering efficiency and to meet the authenticity.With the rapid development of computer graphics, the three-dimensional terrain modeling and visualization are widely researched at home and abroad. The speed of real-time rendering becomes the key factor to determine whether a three-dimensional visualization system is good. But the large amount of data has became the huge obstacles of three-dimensional visualization. Scholars at home and abroad used LOD (Level of Detail) technology widely to solve this problem. The main function of this technology is to simplify the part of flat terrain and distant objects, to reduce the number of drawing primitives, to improve the rendering efficiency under the premise of ensuring visual effects.The content of this paper is:(1) Study the draw technology of large-scale three-dimensional terrain. It introduces the research status and development in the relevant field at home and abroad. LOD (Levels of Details) technology is essential on improving the efficiency of large scale terrain.(2) Through a large number of LOD technology learning, it lists key technologies about three-dimensional terrain rendering and their advantages and disadvantages, including the technology of out-of-core, simplification, visibility culling and crack treatment technology.(3) Based on ROAM (Real-time Optimally Adapting Meshes) algorithm, the display area can be updated in real-time according to the viewpoint position by means of data source processing, field crop and the establishment of evaluation methods, which can avoid rendering superfluous triangular facets.(4) The nodes, which have different hypotenuses, are compulsively split to solve the problem of crack. Through transforming from the indexical coordinate to actual coordinate and utilizing the invalid value, then any scope of undersea terrain can be modeled and visualized based on ROAM, which can guarantee the rendering effect and correctness. By computing and rendering each vertex’s normal and color with GPU, the goal of large-scale terrain modeling and efficient rendering in real-time be achieved, which meets the needs of the high precision, massive undersea terrain roaming.The innovation points of this paper are:(1) Improve the compatibility of dataset through supplement invalid value during data loading.(2) There are blank areas of ROAM on invisible areas. This paper eliminates this phenomenon through invisible areas’ rendering and no simplification.(3) Clear up the limit of mesh size through transforming from the indexical coordinate to actual coordinate.