The Visualization Of River Surface

With the development of digitalization in various fields, water conservationindustry has also carried out many researches on digital basin. However, there are fewresearches on river surface rendering in digital basin areas. For the sake ofconvenience and improving the efficiency of display, most of river visualizationsystems just use a plane, which has a single direction flow texture, instead of the rivermesh. The rendering effect is usually not realistic and the water can not flow alongthe river.The vital factors affecting the reality of water surface are as follow: firstly, watersurface rendering needs vast resources of calculation and display; secondly, creating ariver mesh by complex boundary requires tedious calculation and a long time forgeneration. For the problems mentioned above, this thesis aims at making a study onwater surface real-time rendering, wave models, quick generation of river mesh, theorganization and optimization of the river mesh.In order to improve the efficiency of water surface rendering, a shade programfor controlling the Direct3D programmable pipeline was developed by using HLSL.By the shade program mentioned above, the CPU is displaced by GPU in thecalculation of the water surface illumination model and the rendering effect isdesirable.In this thesis, the height map of the wave was generated by Perlin noise andocean spectrum. The height map and its normal map are used for the flow texture inthe rendering processes, and the height of the river grid is displaced by the height map.The vector data of the river boundary is obtained by using the tools provided in GIS.After the loading of the vector data, the boundary data can be get by resampling, andthen the inner vertex is interpolated by the boundary data. Every vertex in the rivermesh must have a reasonable texture coordinate for mapping the wave texture to theriver mesh. According to the similarities between body-fitted coordinate and the texture mapping, a simple method is proposed to generate the water mesh. Thismethod can generate the mesh faster and is helpful for the organization of data.Generally, river takes up large geographic span areas with a huge amount of meshdata. The method accepted frequently for the organization and optimization of largeamounts of mesh data are LOD and region blocks. Different methods concerning theLOD are compared in this thesis, and the Geomipmaping method is adopt finally togenerate water mesh LOD in real-time rendering. Meanwhile, the river grid blocksare stored by a list structure, the number of visual clipping judgment is reduced andthe efficiency of the calculation is improved.The organization of the mesh can befinished more conveniently.