目的 大部分材质表面都具有一定的细微结构,而这些细微结构的存在增加了真实感图形绘制的复杂性.方法 首先将材质表面的细微结构分为3类:宏观结构、介观结构和微观结构,并对每类结构分别建模:宏观结构采用三角面片建模,介观结构则采用法向图表示,而微观结构直接采用单一的粗糙度表达.然后针对每种结构,分别获得它们的法向分布函数(NDF),并用混合vMF分布拟合.最终屏幕空间每个像素内的法向分布用3个尺度NDF的卷积操作近似获得.此外,在处理环境光照时引入抛物面图(PM)和summed-area table(SAT),满足了动态场景的实时绘制需求.结果 实验结果表明本文方法可以在不同视点范围下生成高真实感的反射效果,并获得实时的绘制性能.结论 本文提出的实时绘制方法能够处理表面材质结构复杂的3维模型在环境光下的真实感反射效果,并支持动态光照和形变物体.

Objective Most materials have some types of fine structures, which inevitably increase the complexity of realistic rendering.Method In this study, these complex structures are further categorized into three scales, namely,macroscale, mesoscale, and microscale. Each scale is modeled with different strategies. In particular, the macrostructures are modeled with traditional triangle meshes because these structures are large and visible under most circumstances. The mesostructures, which are tiny but still resolvable in the image,are represented by normal maps, whereas the smaller microstructures are directly depicted with a single roughness parameter because these structures have a significantly smaller size than the pixel width. For each scale, the normal distribution function (NDF) is obtained and fitted with a vMF distribution or mixtures of vMF distributions. Thereafter, the final NDF is approximated by convoluting each NDF. Furthermore, the paraboloid map and summed-area table are adopted to support real-time rendering of dynamic scenes, including time-varying lighting and deformed meshes.Result Experimental results reveal that the proposed approach can generate photorealistic surface reflections under varying viewpoints at a real-time frame rate. Conclusion A real-time rendering method for rough surfaces with multi-scale properties is proposed in this study. Our method supports dynamic lighting and deformable objects.