Research On3D Visualization Methods For Numerical Cloud Simulation

The simulation of natural world is a heat research topic in computer graphics. Cl ouds, as an important part of nature, have get a lot of attention in many applications s uch as outdoor scene simulation, computer games, meteorological services, the mete orological information processing and so on. If cloud simulation is applied in outdoor scene simulation, the realistic degree of the whole scene will be greatly increased, a nd we will get better visual effect. Meanwhile, the clouds have direct contact with the change of the weather as the important meteorological elements of the synoptic syste m. Simulation of the cloud with real physical significance can not only convey plenty of weather information, but can contribute to the work of the weather forecast perfor med by meteorological department and meteorological service workers. Thus forcefu1support can be provided for various programs of outdoor sports. At present, workers of computer graphics focus on cloud modeling and rendering techniques. But the clo uds simulated are some static or2D cloud this thesis reseach simulation of cloud based on meteorological data of numerical simulation, proposed improve method of cloud model, speed up calculation speed,and combined some draw technology to complete the simulation of cloud. The concrete research content as follows:At the aspect of cloud model, proposed the structure particle system based on hierarchical clustering. In view of the problems that model complex and bad real-time performance of traditional particle systems, first of all, according to the self-similarity between particles to use metric function to find similar particles, at the same time, use hierarchical clustering algorithm to merge the particles that short distance, comprehensive this two kinds of method to establish structured particles model, according to WRF cloud data to obtain the initial contour shape of cloud. Then,by Rayleigh scattering phase function get light intensity and complete illumination render; use interpolation function get the texture of cloud, combines Billboard technique and imposter technique complete render of cloud, speed up the speed of render. Finally, use the sky-box technique add the sky background, enhance overall fidelity of experimental results, complete the simulation of cloud.In the process of visualization of three-dimensional meteorological data, in view of defects that large calculation of selection method of sampling point, and long sampling time, proposed Ray Casting algorithm based on linear octree and use for real cloud data visualization. Improved the selection method of sampling point and data storage structure, reduce the computing time, combined with Blinn-phong illumination model to enhance color render of each element, then, apply by the former backward synthesis formula accumulate pixels, by use of calculation of light and shade show the boundary of cloud, get the visualtion of meteorological cloud data.