目的 已有的基于网格的流体仿真方法存在效率低的问题,不利于物体参与交互,提出一种多尺度活动网格方法用于云场景的仿真以及云与物体的交互仿真.方法 自动选择全局与局部网格的分辨率,对参与交互的物体建立OBB(oriented bounding box)层次包围盒以提高仿真效率.针对云的粘性系数非常小的特点,简化了它们的运动方程与热动力学方程.基于提出的方法对偏微分方程进行了离散化,在方程离散化处理过程中,采用迎风差分方法以保证仿真过程的稳定性.实现过程中,运用GPU的计算性能提高仿真速度.结果 通过云场景的仿真进行了实验,结果表明,可以较为真实地绘制不同时间段的云场景,能满足大规模云场景的仿真需求,实现了云场景以及云与刚性物体交互的实时绘制.结论 相比已有基于网格的方法,本文方法可以容易地在GPU上实现,且提高了仿真效率与绘制图像的真实感.

Objective Previous grid-based fluid simulation methods are inefficient and are thus non-conducive to the interaction between objects and fluids. The multiscale adaptive moving grid method is proposed in this study. The proposed method is used in cloud scene simulation and in interaction simulation between objects and clouds. Method The resolutions of global and local grids can be adaptively selected, and the oriented bounding box hierarchical trees of objects are established to enhance simulation efficiency. Given the small kinematic viscosity of clouds, the controlling and thermal dynamics equations are simplified. Partial differential equations are discretized according to the proposed method. Moreover, upwind difference is applied to ensure the stability of the simulation process. The method is designed to take advantage of GPU computing performance to improve simulation speed. Result Cloud scene simulation is performed in the tests. Results show that the proposed method can render cloud scenes in different periods realistically and thus meets the requirements of large-scale cloud scene simulation. Simulation of cloud scenes and of the interaction between rigid objects and clouds can be realized in real time. Conclusion Compared with the previous grid-based methods, the proposed method can be conveniently realized in a GPU, thus enhancing simulation efficiency and the realism of rendered images.