Study Of Key Technologies In Virtual Seaside City

Three-dimensional virtual city is an important component of digital city. It involves many substrate supporting techniques such as virtual reality, real-time simulation, path planning, human-computer interaction and so on. It is also an advanced research topic in cartology and geographic information system (GIS).This dissertation studies the key technologies in 3D virtual city construction with focus on the following four parts: massive terrain rendering, design and development of real-time navigation system with large-scale scene, path planning technique in 3D virtual scene and nearshore wave simulation in virtual seaside city.1. Massive terrain rendering.Related research about massive terrain rendering is discussed. Then a method based on pyramid structure is proposed to organize and dispatch geometric and texture data of massive terrain. Original data is pre-processed through hierarchy and block-division. Real-time rendering of massive terrain data is realized for only the visible data blocks are loaded into memory according to the view frustum and resolution level is selected according to the position and angle of the viewpoint and corn of normal.2. Real-time navigation system with large-scale sceneOn the basis of discussion on real-time navigation system with large-scale scene, related techniques including rendering acceleration technique, organization and management of virtual scene, rapid elimination and collision-avoidance are addressed. Afterwards, taking virtual campus as an example, real-time navigation system with large-scale scene is realized through VC and OpenGL programming from the viewpoint of integration of virtual reality, multi-media and GIS.3. Path planning technique in 3D virtual sceneRelated research about path planning technique is discussed. Based on analysis of path planning method in GIS and robotics, a new and fast automatic path planning algorithm elastic algorithm is proposed in view of the features of navigation in 3D virtual scene. First, basic path is generated using the projection matrix of the virtual scene; then, the path is optimized using elastic algorithm; finally the optimal path can be got. This algorithm has obvious advantage in solving problems such as collision-avoidance in complex scene and wide walkable region.4. Nearshore wave simulationRelated research about wave simulation technique is discussed. Aiming at the difficulty in nearshore wave simulation and requirement of seaside city virtual scene, a real-time simulation method of nearshore wave is put forward. The problem of wave curving and distortion in nearshore wave rendering is solved by using elliptic cosine functions to construct waveform and refraction simulation of nearshore wave is realized using deformable grids composed of wave rays and wave crests. Meanwhile, a rapid wave rays and wave crests generation algorithm fit for visual simulation is proposed and nearshore real-time simulation is successfully realized.