兼顾采样与光照影响的改进多通路Metropolis光照传播算法
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摘要
为了解决多通路Metropolis光照传播算法局部明暗混合位置采样数量和光照分布不对称的问题,提出一种兼顾采样数量和光照影响的改进算法.首先记录采样数量和光照强度;其次当采样数量达到阈值,根据采样数量和光照强度计算出当前像素八邻域位置的采样权重;最后,以采样权重来影响不同位置的采样比重.采用不同算法在不同光照和材质场景下进行实验,结果表明,该算法改进了明暗混合位置的对称性问题,提升了渲染逼真度.
Aiming at the problem that asymmetry of the sampled number and the lighting distribution at light-dark mixing positions in the multiplexed Metropolis illumination propagation algorithm, an improved algorithm taking into account both the sampled number and the effects of lighting is proposed. Firstly, the sampled number and the light intensity of samples are recorded. Secondly, when the sampled number reaches a threshold value, the sampling weights of the eight-neighborhood pixels are calculated according to the sampled number and the light intensity. Finally, the weight is used to influence the sampling proportion of different positions. The results of experiments conducted in different scenarios containing different lighting and materials using different algorithms show that the algorithm improves the symmetry of the light-dark mixing positions and enhances the rendering fidelity.
Aiming at the problem that asymmetry of the sampled number and the lighting distribution at light-dark mixing positions in the multiplexed Metropolis illumination propagation algorithm, an improved algorithm taking into account both the sampled number and the effects of lighting is proposed. Firstly, the sampled number and the light intensity of samples are recorded. Secondly, when the sampled number reaches a threshold value, the sampling weights of the eight-neighborhood pixels are calculated according to the sampled number and the light intensity. Finally, the weight is used to influence the sampling proportion of different positions. The results of experiments conducted in different scenarios containing different lighting and materials using different algorithms show that the algorithm improves the symmetry of the light-dark mixing positions and enhances the rendering fidelity.
引文
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[2]Kollig T,Keller A.Efficient bidirectional path tracing by randomized quasi-Monte Carlo integration[M].Heidelberg:Springer,2002:290-305
[3]Tabellion E,Lamorlette A.An approximate global illumination system for computer generated films[J].ACM Transactions on Graphics,2004,23(3):469-476
[4]Bao Shiqiang.The study of bidirectional path tracing based Metropolis global illumination method[D].Tianjin:Tianjin University.School of Computer Science,2007(in Chinese)(鲍世强.基于双向路径追踪的Metropolis全局光照算法的研究[D].天津:天津大学计算机学院,2007)
[5]Veach E,Guibas L J.Metropolis light transport[C]//Proceedings of the 24th Annual Conference on Computer Graphics and Interactive Techniques.New York:ACM Press,1997:65-76
[6]Kelemen C,Szirmay-Kalos L,Antal G,et al.A simple and robust mutation strategy for the Metropolis light transport algorithm[J].Computer Graphics Forum,2002,21(3):531-540
[7]Hachisuka T,Kaplanyan A S,Dachsbacher C.Multiplexed Metropolis light transport[J].ACM Transactions on Graphics,2014,33(4):Article No.100
[8]Zeng Zuo,Fang Mei’e,Ma Lizhuang,et al.Improved multiplexed Metropolis light transport[J].Journal of Computer-Aided Design&Computer Graphics,2016,28(9):1459-1464(in Chinese)(曾笮,方美娥,马利庄,等.改进的MMLT全局照明渲染算法[J].计算机辅助设计与图形学学报,2016,28(9):1459-1464)
[9]He Huaiqing,Chen Shuai,Liu Haohan,et al.An improved algorithm for sampling distribution based on MLT[J].Journal of Shenyang University of Technology,2017,39(6):646-653(in Chinese)(贺怀清,陈帅,刘浩翰,等.一种针对MLT的采样分布改进方法[J].沈阳工业大学学报,2017,39(6):646-653)
[10]Nicholas M,Ulam S.The Monte Carlo method[J].Journal of the American Statistical Association,1971,14(1):151-167
[11]Andrieu C,Doucet A,Holenstein R.Particle Markov chain Monte Carlo methods[J].Journal of the Royal Statistical Society,2010,72(3):269-342
[12]Kajiya J T.The rendering equation[C]//Proceedings of the 13th Annual Conference on Computer Graphics and Interactive Techniques.New York:ACM Press,1986:143-150
[13]Veach E.Guibas L J.Optimally combining sampling techniques for Monte Carlo rendering[C]//Proceedings of the 22th Annual Conference on Computer Graphics and Interactive Techniques.New York:ACM Press,1995:419-428
[14]Tong Yubing,Zhang Qishan,Qi Yunping.Image quality assessing by combining PSNR with SSIM[J].Journal of Image and Graphics,2006,11(12):1758-1763(in Chinese)(佟雨兵,张其善,祁云平.基于PSNR与SSIM联合的图像质量评价模型[J].中国图象图形学报,2006,11(12):1758-1763)
[15]Wang Z,Bovik A C,Sheikh H R,et al.Image quality assessment:from error visibility to structural similarity[J].IEEETransactions on Image Processing,2004,13(4):600-612