三维动态云模拟

Simulation of 3D Dynamic Clouds

云在户外场景的模拟中起着重要的作用.基于云的物理特性,在云建模方面,在三维网格单元上赋予云的速度、密度、湿度等物理属性值,利用Navier-Stokes方程描述云的聚散和运动,丰富了云模型的物理特性;为了表现云的扩散作用,加入黏性项和漩涡性,更真实地表现了云的湍流效果;同时在模拟域中加入一个随机函数,实现了云在运动过程中外形的随机性和不确定性;在云渲染方面,考虑太阳光照方向和视点方向的光照强度,使用单向散射光照模型,提高了云的渲染速度.采用迭代更新纹理数据值的同时改变模拟域的世界坐标值的方法实现云的动态飘动效果.实验证明该方法生成的云真实感强,实现了三维动态云的模拟.

Clouds play an important role for creating realistic images of outdoor scenes.We put the velocity,the density and the humidity on 3D grids in clouds.The clouds motion is modeled by the Navier-Stokes equations.In order to performance the spreading effect realistically,we put the viscosity and the burble into the Navier-Stokes equations to control clouds.And a random function is put into the simulation space to show the different shapes of clouds.According to the light intensity of the sunlight and the viewpoint direction,we use a simple single scattering lighting model as rendering clouds and the rendering speed was improved.Then,we iterative update texture data and change the coordinate of simulation space in world space to performance the dynamic movement of clouds.Experiment show that the reality of clouds generated by our method is well and the 3D dynamic clouds simulation was achieved.