基于BSP树的启发式阴影生成算法

A algorithm of Heuristic Shadow Based On BSP Tree

阴影的生成在虚拟现实领域一直是个难题,特别是针对动态光源的大规模场景,目前还没有较成熟的阴影算法。通过对现有阴影生成算法和场景组织算法的研究,该文提出了基于二维空间分割树(BSP树)的启发式阴影生成算法:首先创建场景BSP树,随着观察者视点的改变,选取视剪裁体内的节点创建以光源为视点的遮挡体BSP树,然后通过对该BSP树的遍历拣选出阴影启发区内的物体,经过处理后BSP树只留下一些生成阴影必要的多边形大大减少了计算量,最后能够快速生成阴影。

Shadow plays an important role in realistic image synthesis. But the building of the shadow is a difficult problem in the field of the virtual reality. Nowadays, there is not a better algorithm in the mass scene. By the studying of the algorithm of building shadow and the organization of the scene, this paper describes the algorithm of heuristic shadow based on the Binary Space Partitioning trees （ BSP trees）. At first, we build a BSP tree of scene, and select the node of the tree, which is clipped by the frustum of the sight. Then we build the BSP tree of the occlusion using the selected node and select the objects which are in the heuristic zone of the shadow again. After select twice, there are some polygons that are necessary to the building of the shadow in the BSP tree of the occlusion. So, we can build the shadow rapidly.