Keep region for constructing LOD of terrain regular mesh

We present an improved ROAM algorithm for keeping region when rendering terrain. Concerning the region broken problem, of ROAM algorithm in rendering terrain, a method of keeping region in rendering terrain with enhancing the triangle splitting condition is proposed. The concept of optimum triangulation for region is used to set the splitting vertex and its parent active. The rending algorithm sets status of the active vertex according to the view direction and the distance between viewpoint and region, and produces the terrain region's level of detail. The results of experiments show that our algorithm with LOD has a satisfactory performance in keeping region during rending terrain.