环境光照下的毛发渲染与外观编辑

Interactive Hair Rendering and Appearance Editing under Environment Lighting

提出一种复杂环境光照条件下交互级毛发绘制与外观编辑的算法,其中光源采用球面径向基函数(SRBF)表示.推导出了一个可以用来精确表达Marschner毛发散射函数(Marschner S R,Jensen H W,Cammarano M,et al.Light scattering from human hair fibers.ACM Transactions on Graphics,2003,22(3):780-791)[2]的简洁一维圆高斯表达,该表达可以高效地以解析形式计算每个SRBF光源与毛发散射函数的积分,因此支持高效的单次散射和多次散射计算.与前人工作不同,文中算法完全在运行时进行所有的计算,不需要昂贵的预计算步骤,因此可以动态地改变毛发的散射参数.分析表明,文中提出的近似表示是精确且简洁的.此外,该算法可以处理椭圆头发截面的情况.通过在GPU上实现,文中算法可以达到交互帧率.

We present an interactive algorithm for hair rendering and appearance editing under complex environment lighting represented as spherical radial basis functions（SRBFs）.Our main contribution is to derive a compact 1D circular Gaussian representation that can accurately model the hair scattering function introduced by references（Marschner S R,Jensen H W,Cammarano M,et al.Light scattering from human hair fibers.ACM Transactions on Graphics,2003,22（3）： 780-791） [2].The primary benefit of this representation is that it enables us to evaluate,at run-time,closed-form integrals of the scattering function with each SRBF light,resulting in efficient computation of both single and multiple scatterings.In contrast to previous work,our algorithm computes the rendering integrals entirely on the fly and does not depend on expensive precomputation.Thus we allow the user to dynamically change the hair scattering parameters,which can vary spatially.Analyses show that our 1D circular Gaussian representation is both accurate and concise.In addition,our algorithm incorporates the eccentricity of the hair.We implement our algorithm on the GPU,achieving interactive hair rendering and simultaneous appearance editing under complex environment maps for the first time.