基于快速傅立叶变换的实时动态草叶绘制

摘要

大范围自然环境已成为当今3D游戏和仿真系统中不可或缺的关键因素.而植被又是自然环境中必不可少的成分,大面积植被有助于提高仿真场景的沉浸感.准确绘制几何草叶往往要诉诸于大量面片绘制,计算复杂度随着几何面片的增加而显著增加.同时要使叶片随风摆动,叶片的几何模型就要动态修改,这无疑使场景实时渲染变得困难重重.因此减轻数据传输、图元绘制压力的方法以及简单可靠的模型网格运动控制方法的应用及其运行效率在运动植物叶片绘制过程中就显得尤为重要.减轻传输压力需要尽量少的数据,提高绘制质量需要尽量多的数据,解决这对矛盾需要少量输入大量输出.利用当今图形硬件的几何着色器,和顶点着色器传输进来的少量顶点数据动态创建代表叶片的图元条带,是减少传输和绘制面片数量的有效手段.采用基于快速傅里叶变换(FFT)技术控制叶片的运动,是一种简单有效的运动控制方法,可以使大量随风摆动叶片的实时绘制成为可能.%Wide range natural environment has become the indispensable factor of 3D games and simulation systems.Vegetation is an essential element of the natural environment.It helps to improve the immersion of simulation scenarios.Accurate rendering of the geometry based grass often resorts to drawing a large number of patches.The computational complexity will significantly increase when the number of the geometric patches increase.When the grass blade is moved by the wind, the geometry model of the grass must be dynamically changed.It will undoubtedly make the real-time rendering difficult.The method of the decrease of the data transfer and the magnitude of the rendering primitive and the simple dependable flow control method are important in the rendering of the range natural environment with vegetation.Reducing the data delivery pressure and improving the rendering quality are contradictory.A small amount of input and a large number of output are required to resolve this contradiction.The dynamically created primitive strip by the GeometryShader and the small amount of data passed by VertexShader is the effective means of reducing the number of transmission and rendering.The FFTbased flow control method make the real-time rendering dynamic grass blade possible.