反射剖面精确拟合的次表面散射计算方法  

Subsurface Scattering Computation with Accurate Reflectance Profile Fitting

作　　者：梁仕宇 高阳[1,3] 丛宇 郝爱民 LIANG Shi-Yu;GAO Yang;CONG Yu;HAO Ai-Min(State Key Laboratory of Virtual Reality Technology and Systems(Beihang University),Beijing 100191,China;School of Computer Science and Technology,Xidian University,Xi’an 710071,China;Reserch Unit of Virtual Body and Virtual Surgery Technologies,Chinese Academy of Medical Sciences,Beijing 100032,China;Unidraw Virtual Reality Technology Research Institute Co.Ltd.,Beijing 101300,China)

机构地区：[1]虚拟现实技术与系统国家重点实验室(北京航空航天大学),北京100191 [2]西安电子科技大学计算机科学与技术学院,陕西西安710071 [3]中国医学科学院虚拟人体和虚拟手术技术创新单元,北京100032 [4]北京众绘虚拟现实技术研究院有限公司,北京101300

出　　处：《软件学报》2023年第8期3757-3773,共17页Journal of Software

基　　金：国家自然科学基金(62002010);北京市自然科学基金(4214066);中国医学科学院医学科学创新基金(2019-I2M-5-016);北京市生物医学工程高精尖创新中心(ZF138G1714)。

摘　　要：近年来,随着电影、游戏、虚拟现实应用等对真实感要求的不断提高,针对人体组织、牛奶等半透明材质的实时渲染变得越发重要.针对当前大部分次表面散射计算方法难以正确估计散射范围的问题,提出了一种全新的次表面散射计算方法用以精确表示最大散射距离.首先,针对暴力蒙特卡洛光子追踪结果进行模拟,以得到反射剖面结果.其次通过多项式模型进行反射剖面拟合,计算精确着色点处的最大散射范围.最后,提出了一种新的重要性采样方案以减少蒙特卡洛所需的采样数,进一步提高计算效率.此外,方法所需的参数仅由着色点上的反射率以及材质平均自由程提供,以便于灵活调整渲染效果.实验证明,所提模型避免了之前对于散射范围的错误估计,对材质反射率复杂的区域具有更好的渲染精度,且渲染速率满足实时要求.Recently,with the continuous improvement of realism requirements of movies,games,virtual reality applications,etc.,the real-time rendering of translucent materials such as human organs and milk has become more and more important.For most of the current subsurface scattering calculation methods,it is difficult to correct the scattering range.To tackle this estimation issue,a new subsurface scattering calculation formula is proposed to accurately represent the maximum scattering distance.First,the brute-force Monte Carlo photon tracking results are simulated to obtain the reflectance profile results.Second,the selected polynomial model is used to fit the reflectance profile to calculate the precise maximum scattering range at the shading point.To begin with,a new importance sampling scheme is proposed to reduce the number of Monte Carlo samples,thereby increasing the computational efficiency.In addition,the required parameters are only provided by the reflectance on the shading points and the mean free path of the material,so as to flexibly adjust the rendering effect.Experiments results have shown that the proposed model can avoid the previous error estimation of the scattering range,and has more accurate rendering results of the complex reflectivity area of the material.Meanwhile,the rendering rate meets real-time requirements.

关 键 词：次表面散射 半透明材质 真实感渲染 函数拟合 实时渲染 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]