层次可见性与层次细节地表模型相结合的快速绘制

大规模地表模型的实时绘制是虚拟现实技术中重要的研究课题之一。为了加速地表模型的绘制，人们采用视点相关的动态多分辨率层次细节模型方法，但是算法效率依然有待提高。该文提出一种层次可见性与层次细节地表模型相结合的快速地形绘制方法。算法旨在利用地表模型所具有的horizon特性在预处理中为地表多分辨率块模型建立相应的层次“块”可见性结构，快速判定地形块相对于当前视点的可见性，以减少多分辨率模型中模型细节的处理和绘制三角形的数目。同时为消除地表模型层次变化所带来的可见性错误，算法提出一种层次结构可见性计算方法，以修正多分辨率模型所带来的可见性动态变化。实验结果表明算法有效地提高了绘制效率，是可行的。

Combination of Hierarchical Visibility with Level of Detail Terrain Model

Real time rendering of large scale terrain is one of the important subjects in virtual reality technology. This paper puts forward a fast terrain rendering algorithm that combines hierarchical visibility with level of detail model for terrain walk through. The main idea of the algorithm is to make use of horizon characteristic of terrain to set up the corresponding block visibility structure for dynamic multi resolution model in preprocessing stage. With the block visibility structure, the visibility of all terrain block can be quickly tested. Since the invisibme terrain quads are culled, the number of triangles to be processed and rendered reduces heavily. At the same time, in order to eliminate the visibility error caused by terrain model changing in different level. This paper puts forward a hierarchical visibility computing method to revise the dynamic change on terrain model. The experimental result indicates efficiency of the algorithm.