基于球体追踪的动态视差遮挡映射算法

Dynamic Parallax Occlusion Mapping Algorithm Based on Sphere Tracing

提出了一种利用球体追踪进行逐像素光照计算的动态视差遮挡映射算法.该算法先对纹理的高度图进行预处理,为纹理高度空间内的任意点到高度图中保存的实际表面建立最短距离映射,并在图形处理单元(GPU)像素着色器上利用距离映射进行球体追踪,获得准确的纹理视差偏移值,同时加入纹理的自遮挡效果,生成软阴影.算法还利用可编程GPU管线进行硬件加速,以满足实时渲染的要求.与在高度图上进行固定步长线性采样的动态视差遮挡映射算法(DPOM)相比,所提算法的处理效率可提高3.3倍,并且不会出现DPOM算法在步长较大时出现的纹理漂浮现象.

A dynamic parallax occlusion mapping algorithm based on per-pixel sphere tracing is proposed, in which the height map of the texture is preprocessed to build a shortest distance map for the practical surface saved in the height map from any points within texture height space. Then, the sphere tracing is carried out to obtain the accurate parallax offset of the texture in a pixel shader of graphic processing unit （GPU） by using distance map. Meanwhile, the self occlusion effect of texture is added to form the soft shadow. Applying the programmable GPU pipeline, the algorithm adopts hardware acceleration techniques to satisfy the needs of real-time rendering. Comparing with the dynamic parallax occlusion mapping （DPOM） which uses linear sampiing with fixed step in the height map, the efficiency of the proposed algorithm can be increased by 3.3 times, and the texture floating phenomenon that exists in DPOM when step is bigger will not appears.