用于地面可视化的DEM四叉树改进

An Improved Quadtree of DEM for Terrain Visualization

四叉树表示在数字高程模型（ＤＥＭ）的压缩存储和地面可视化中占有非常重要的地位。此文吸收了ＤＥＭ普通四叉树表示和塔形分层表示的优点，提出了一种改进的四叉树结构。它主要是在结点的数据域中增加了高程最大值和最小值项，并把四叉树线索化了。经过改进的四叉树结构使ＤＥＭ在地面可视化中进行的光线追踪时，光线追踪效率得到了提高。

Quadtree representation of DEM is of importance in DEM compression and terrain visualization. An improved quadtree is proposed, which has the advantages of both an ordinary quadtree and a pyramidal structure. Each node of the improved quadtree is added with a maximum height value and a minimum height value, and the whole quadtree is threaded, thereby making raytracing efficient in terrain visualization.