Terrain Simplification Algorithm Based on Morton Compressing in Block and Hybrid Generating Rule

The method of compressing digital elevation model（DEM）using Morton code can only be applied to the relatively flat terrain.In order to avoid the limitation of the method,this paper presents a Morton compressing method in terrain data block partition based on the surface roughness.The 2-level dividing method is used in terrain partition.Only the terrain blocks with lower surface roughness are encoded and compressed,which could reduce the amount of reading DEM data and improve the compression speed.In the process of modeling,the generating rule based on the local terrain entropy is discussed and improved to form a view-dependent local entropy rule.Then,combining the improved rule with Phong illumination model into our hybrid rule,the algorithm in this paper uses viewdependent local entropy rule to simplify terrain near and Phong illumination model to simplify terrain far.The experimental results demonstrate that the proposed method can keep the local details of terrain and simultaneously reduce rendering triangles efficiently,improving effects of terrain visualization.