GIS Park

The LOD model construction of terrain is an important technology in the research of 3D terrain visualization and application. The real-time 3D modeling and visualization is a big difficulty related to the current computer hardware. Almost the methods focus on LOD modeling and rendering technology. The thesis does research in two aspects:1. Dynamic culling based on view angle. Through the basic theory of frustum culling, the thesis proposes a dynamic culling method based on view angle and LOD technology. Through setting the resolution levels, the method can establish the bounding sphere that related to the resolution levels dynamically. It can estimate the relation between the sphere and the terrain nodes more efficiently, thus avoid the wrong estimating and node decomposing, and set up the LOD model more quickly.2. Construction of LOD model based on terrain TIN model. Based on the above culling method and point deletion theory, the algorithm constructs a static LOD model. It adds the restriction of terrain properties, maintenances the change of the terrain trending. The algorithm resolves the problem of split through the method of boundary sampling and local triangulation, It also resolves the problem of incoherence between two layers, realizes the real-time net updating.