Application Study Of Fractal In Virtual Reality Scenes

Virtual Reality has been widely used in the fields such as computer simulation, digital earth, game and entertainment, etc. These applications need not only realism complex Virtual Environment, but also require the user to interact with the virtual scenes at interaction frame rate. As long as meeting the real-time rendering, the user can feel the virtual environment which is the same as the real world and immerse into the environment. However, Virtual reality communities and other visualizations have always faced the problem that their "desirable" visualization dataset sizes are one or more orders of magnitude larger than what the hardware can display at interactive rates. Thus Realistic rendering of 3D terrain scenes is a challenging subject.Fractal theory, 3D terrain modeling and virtual scene are discussed in details. Firstly, based on OpenGL library and its work principle, the process of 3D real-time terrain surface rendering is analyzed at length. Some methods are presented to improve rendering effects and to speed up graphic display. Secondly, on the basis of fractal theory, the terrain simulation is systematically studied and carried out by using fractal Brown motion (FBM) method. For the fractal terrain simulation, the "diamond-square" algorithm based on random midpoint displacement (RMD) is given in detail. Thirdly, in order to render 3D terrain in real time, this paper presents an improved LOD algorithm. This algorithm firstly simplifies the DEM data by using Mortan coding principle and stores the simplified data with an unfull quatree. Then, it builds the real-time continuous LOD based on this unfull quadtree according to the relationship between viewer position and grid object space error. The author brings out a method named"find the neighbors layer by layer"to patch the cracks between different layers and the procedures to find the different type neighbors are presented in this paper. Finally, it wipes off the invisible grids through back-culling algorithm. In order to improve the rendering speed during the programming, it uses Hibert filling curve method to store and interleaved quatree method to access the unfull quatree nodes. The author uses the improved method to simulate the terrain area and obtains a good effect.