三维地形模型流式传输方法

为满足基于网络的大规模地形漫游系统中有限的网络带宽与海量地形数据之间的矛盾，提出了一种三维地形流式渐进传输方法。该方法在服务器端对地形数据进行预处理，首先将地形数据进行分块，再对分块后的数据进行小波变换，最后用多级树集合分裂(SPIHT)算法将变换后的数据组织成多条渐进码流。客户端在运行时根据视点的位置，漫游的速度和方向确定周围各地块的传输规则，使各地块的传输量进行自适应调整，同时采用二级缓存机制缓解网络拥塞时数据供应压力。实验表明，该方法能很好地支持客户端基于GPU的多分辨率地形构造并在各种网络带宽情况下保持较高的绘制帧率，保证网络交互绘制的实时性。

Method for streaming transmission of 3D terrain model

To solve the contradictions between the limited network bandwidth and the mass of terrain data, a new approach of terrain data streaming transformation was proposed. The approach partitioned the terrain data on sever, applied wavelet transform and used SPIHT coding algorithm to organize the terrain data into multiple progressive compressed streams. On the client, transmission quantity of each terrain block around the viewpoint was designed to be adaptively adjusted according to viewpoint position, alterative direction and speed of the viewpoint. At the same time, caching method storing terrain blocks around the viewpoint in client was also designed to lighten the stress of data supply when the network was congested. The experimental results show that the approach can adapt to the rendering algorithm based on GPU and keep a good frame rate to ensure the continuity of the terrain rendering.