中文摘要：

针对地形模型随视点简化时,容易引起边界的变化,使得地物模型与地形模型简化过程中产生“裂缝”或翻转现象的问题,文章提出一种改进方法：在对三维地形和地物进行集成后,采用递进格网表示方法并在边折叠过程中采用条件约束对其简化;在边排序的基础上,根据顶点重要度进行排序。该方法优点是计算时间短,且权值定义能够很好地反映局部几何特征,能够保持三维地形、地物模型边界原始信息和格网三角面的基本方向,并消除集成模型之间的“裂缝”或悬空现象。最后通过对整个三维场景进行动态实时绘制,证明该方法具有良好的可视化效果。

英文摘要：

Aiming at the problem that it is easy to cause the boundary change when the terrain model is simplified with the viewpoint, making the terrain model and the feature model engender gap or flip during the simplifying process, the paper proposed an improved method： after the integration of 3D terrain and feature model, the progressive mesh method and the edge folding simplification process based on the constraint conditions were used; and the threshold value was selected to determine the position of the folding vertex and the edge weight factor was specially considered according to the vertex degree. The advan- tage of the method includes： short computation time, suitable weights for telling local geometric characteristics, complete 3D terrain and feature boundary information, original direction of the mesh triangular surface, and ideal status without the gap or the dangling phenomenon between models. Finally it was proved that the method would have a good visual effect through the dynamic real-time rendering of 3D scene.