Simplification Algorithm and Format Organization for Terrain Grid Based on Holding-Boundary

To deal with cracks between terrain blocks,one approach is to repair them precisely on primitive level,which consumes much computing resource,while another masks them visually,causing incoherence in geometric and texture spaces.Based on Melax's fast polygon reduction algorithm,a terrain simplification algorithm was proposed that used holding-boundary and edge collapse.Firstly concepts of holding vertex and controlling vertex were defined,and quantity choice of holding vertex and reduction strategy of controlling vertex were provided.By improving edge collapse rules and cost formulae,grid simplification with fixed boundary was realized.Then according to the clustering hierarchy representation,simplified grids were overlapped with original regular grids,using vertex indices to ensure fast and batched terrain manipulations.Thus the terrain format featuring holding-boundary was presented.Experiment results show that the proposed algorithm can lower densities of boundary primitives and maintain more terrain features;the terrain format shows high frame rate and seamless visual effect in flight cruising test.