树木运动和降雨均是常见的自然现象。随着计算机图形学的发展，树木运动和降雨的模拟在游戏、影视、广告、虚拟现实等领域得到了广泛应用。能否逼真而实时地生成树木运动和降雨效果，直接影响整个虚拟场景的真实感。本文主要研究树木在风雨中运动的可视化模拟。整个研究过程，主要分为以下三个部分来实现。 首先，研究了降雨的模拟方法。该方法在分析了粒子系统实现原理以及雨滴粒子行为的基础上，建立了恰当的雨滴粒子模型，并通过在极坐标内生成雨滴粒子的方法，提高了粒子的利用率。其中，就风对于雨滴的干扰作用进行了精确的几何计算，模拟出了逼真的雨滴运动过程，并通过OpenGL中纹理贴图技术完成了雨滴的绘制。实验结果表明，通过该方法生成的雨景真实自然，实时性强，具有一定的实用价值。 其次，在对树叶表面雨滴行为分析的基础上，讨论了雨滴与树叶的交互作用方法的实现。针对雨滴在树叶表面静止的情况，通过对雨滴粒子标本变形生成树叶表面雨滴形状。对雨滴在树叶表面的流动情况进行简化，提出了一种纹理替换的方法来绘制雨滴在树叶表面的流动。根据提出的方法实现了树叶表面雨滴的静止和流动效果的绘制。实验表明该方法简单可行，真实感较强。 最后，将树木在风中的运动和降雨集成实现了树木在风雨中运动的模拟。将雨景加入到已实现的风中树木运动的三维场景中，根据提出的雨滴粒子与树木的碰撞检测方法来确定雨滴粒子的生命周期以及与树叶碰撞的位置；对于碰撞到树叶的雨滴重新赋予生命周期并改变和该雨滴碰撞的树叶纹理；加入声音效果与雾化效果来使得整个三维场景更加逼真。最终的三维效果显示，生成的三维场景真实感较强。 在VisualC++下，结合OpenGL实现了树木在风雨中运动的可视化模拟。实验结果表面，本文的方法有效，仿真结果真实。

Both tree motion and rainfall are common natural phenomena. With the dramatic development of computer graphics，tree motion and rainfall have a wide range of application in Games, Film and Television, Advertising, Virtual Reality,ect. Whether We could generate the tree motion and rain effectively and in the time is in a direct line to the sense of reality and immersion in virtual scenes.Therefore,in this article we make the research on the visual simulation of tree motion in wind and rain.The whole research includes three parts as follows: Firstly,study the simulation method of rainfall.Model a proper raindrop particle by analyzing the reaiizing principie of particie system and the action of raindrops particles;Improve the utilization rate of raindrops particles by generating the raindrop particles in polar coordinates;Realistically simulate the movement of raindrops particles by precise geometric calculations for the wind’s influence to the raindrops particles;Render the raindrop by texture mapping in OpenGL.The results show that using this method makes the simulation of rain inatural and high in real-time,which guarantees its practical values. Secondly,discuss the implement methods of the interaction between the raindrop and the leaf based on the anlysis for the action of raindrop on leaf surfaces.produce the shape of raindrop on leaf surfaces by the distortion of the shapes for the raindrop specimens; simplify the flow of the raindrop on the leaf surfaces and come up with an method, Texture substitution, to render the flowing of raindrop;Implement the static raindrop and the raindrop flow along the leaf vein according the methods we proposed. Experiments show that this method is practicable and simple and more realistic. the whole implementation of Finally, combine the Visual Simulation of Tree Motion in Wind and Rainfall to achieve the Visual Simulation of Tree Motion in Wind and Rain. add the rain to the three-dimensional scene Which have finished about tree movement in wind and determine the lifecycle of raindrops and the position which it collide with the leaf based on the method we have proposed;give the life cycle to the raindrops which hit the leaves, also change the texture of leaves which raindrops hit;enrich the whole three-dimensional scene by adding sound and fog. The final result proves the high fidelity the three-dimensional scene. Implement the simulation of tree motion in wind and rian by VC++6.0 and OpenGL. Experiments show that the method is effective, and the simulation result is realistic.