一种支持大规模多种精度地形的实时绘制算法

A Real-Time Rendering Method for Large Terrain Including Details in Different Resolutions

为加强大规模地形数据的表现能力,通常采用地形叠加或地形编辑等方法在局部地形数据上构建更高精度的细节模型.因而如何将大规模地形数据与具有高精度的细节数据进行实时融合与绘制成为一个迫切需要解决的问题.基于Geometry Clipmap方法对这一问题开展研究,给出了一种支持大规模多种精度地形的实时绘制算法.在预处理阶段,对大规模地形数据采用clipmap结构进行组织,对细节数据使用mipmap结构进行组织;在运行阶段,重点针对clipmap更新所引起的不同种精度数据间特有的"F"形空洞进行分析和处理,使用过渡带结构对空洞区域进行修补,并对修补后的顶点进行了平滑处理.实验结果表明,该方法有效解决了"F"形空洞并支持大规模地形及细节数据的实时绘制.

In order to improve the capacity of performance of large scale terrain data,users usually create detail data by editing way such as changing the features in some regions and add other details to original terrain data in some simulation training or video games. However,it＇s a big challenge to merge and render large terrain and additional detail data in real time due to different resolutions. In this paper,a new algorithm is given to handle this problem. In preprocessing stage,the algorithm constructs large terrain by clipmap structure as to integrating advantages of geometry clipmap method and constructs the detail data in mipmap way. In real-time rendering phase,the phenomenon of ＂F＂ hole area appears at the boundary between the large terrain and the detail data when clipmap structure is being updated. In order to solve this problem,a new structure called transition strip is proposed which can merge the data in different resolutions well in run time,the transition strip structure is given which is composed of two sides,the vertexes in lower resolution and vertexes in higher resolution. Some transition strips are used to fill the ＂F＂ hole area and these transition strips are close to each other in practice. And a fast triangulation method used for rendering. The results of experiments show that the transition strip can solve the problem of ＂F＂ hole area and can render both large terrain and details data in real time.