Research And Implementation Of Key Techniques Of Fractal 3D Terrain Generation

The generation technology for virtual terrain attracts more and more attentions at present. It has been widely used in navigation based on 3D terrain, simulation of battlefield, VR, landscape, programming of city, outdoor games, movie production, etc. The thesis focuses on the following theoretical and methodological studies: terrain data acquirement, fractal terrain simulation, 3D terrain rendering, terrain simplification and multi-resolution terrain representation, real-time optimization, and terrain texture synthesis. Combing with the application of navigation based on 3D terrain. The major contribution includes:1. Based on OpenGL library and its work principle, the processes of 3D surface rendering are analyzed, including modeling, spatial transform, illumination processing, visible area determination and shading. Some methods are presented to improve rendering effects and to speed up graphic display.2. The terrain data of different sources are studied. The varieties of generated virtual terrain are compared. Then an improved method is presented, which optimizes coplanar simplified criteria. The method implements the flexible control of terrain features, by integrating fractal terrain data, noise terrain data and terrain data which are obtained form altitude graph. Finally, the optimized methods are applied to algorithm. The experiment shows that supplemented simplified criteria are effective, and the whole terrain rendering frame is fluent and interactive.3. The technology for real-time multi-resolution terrain rendering is analyzed in details. A new simplification criterion is presented on the basis of Lindstrom's criteria. The experimental results indicate that the new criterion is efficient and can solve the triangle redundancy when rendering the coplanarity incline.4. A real-time multi-resolution terrain-rendering frame structure is established. It employs longest-edge bisection, and contains a series of operation such as establishing nested hierarchy sphere, real-time refinement, view frustum culling, geomorphing. Meanwhile, memory-mapping and multithread technologies are also adopted.5. Soft shadow algorithm is studied which could enhance the real sense of 3D terrain, then, through combing the features of 3D terrain, it is put into application. After shadow enhancement algorithm is improved, on the basis of picturing terrain surface framework, shadows are added to terrain according to light sources in different locations. In this way, 3D solid real sense could be further improved.