Simulation And Rendering Of Anistropic Scattering Clouds In Sky Scene Based On Distribution Function

Funding by the Nation "863" Projects "the space XXXX," we researched the space battlefield simulation. This article is a sub-project of the project to study the modeling and rendering of clouds in the space roaming system. The cloud, as an important part of the space battlefield scene, has a significant impact on the authenticity of the simulation results. However, the space battlefield is a huge and complex system. There are enormous elements. The cloud is only a very small part. So the cloud simulation can only occupy very few resources. Because the physical process of the cloud formation is extremely complex and the shapes are diverse. The states are also constantly changing. So to simulate multiplicity shapes and high real-time cloud to meet the needs of the space battlefield environment becomes very meaningful.Firstly, for the low real-time cloud simulation with particle system, a cloud modeling method based on distribution function was proposed. The properties of particles were controlled by setting different distribution functions. Trajectory function was used to control the disappearance of particles and so to control the shape of the cloud. This solves the real-time effects brought by particle system due to large number of particles and complex movement laws.Secondly, for the problem of complex path of light spreading in the clouds and the large amount of texture data, a table query technology based on shadow relation table and metaball light texture database was proposed. In pre-processing stage, corresponding texture was calculated and stored in the shadow relation table. And in real-time rendering stage, texture data was obtained through the index query methods. It will reduce the rendering time.Then, in real-time rendering stage, texture patches and Impostor texture mapping were combined to meet the requirements of the cloud detail degree by different distance from perspective; Scaling errors generated by the Impostor texture were amended. In order to show the various anisotropy scattering characteristics of light in the clouds, scattering phase function was optimized to achieve the multiple anisotropic scattering of cloud particles.Finally, a single cloud system and clouds adding to the space roaming system were designed by using VC + + and OpenGL programming tools in ordinary PC. Experiment results show that: the cloud simulated by us has better authenticity and high real-time efficiency, it can be used to the space battlefield environment.Our research is a discussion and confirming on the authenticity and real-time issue on cloud simulation, which is of great significance for the space battlefield simulation.