基于体素锥追踪的全局光照算法
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摘要
提出一种全局光照的计算方法,使用体素结构存储简化场景的光照信息,并通过体素锥追踪方法来收集光照信息,计算间接光照。在计算过程中,每帧只更新动态场景的体素结构,既可以支持动态光源,又避免了更新静态场景的时间消耗。通过各向异性过滤生成的方向性层级结构,将简化的体素场景及光照信息压缩存储在三维纹理的渐近贴图中,从而减少存储开销。利用体素锥追踪收集体素结构中存储的出射辐射度及遮蔽值来计算环境遮蔽、软阴影等全局光照效果。实验结果表明,所提方法可计算多种全局光照效果,并具有较好的绘制效率,在复杂的场景下单帧时间少于33.3 ms。
In this study, we propose a global illumination algorithm based on the voxel structure. In the proposed algorithm, the voxel structure is used to store the illumination information of a simplified scene, and the indirect illumination effects can be obtained by collecting the illumination information using the voxel cone tracing method. Only the voxel structure of the dynamic scene is updated in each frame, which supports dynamic light sources and avoids unnecessary calculations for updating the static scene. The voxel structure is a directional hierarchical structure generated by anisotropic filtering, which can be compressed and stored in a mipmapped three-dimensional texture, reducing the storage costs. It is possible to calculate the global illumination effects, such as ambient occlusion and soft shadow, by collecting the outgoing radiance and occlusion values stored in the voxel structure using the voxel cone tracing method. The experimental results demonstrate that this approach can obtain various global illumination effects and exhibit a decent rendering efficiency. Furthermore, the single-frame time is less than 33.3 ms in case of complex scenes.
In this study, we propose a global illumination algorithm based on the voxel structure. In the proposed algorithm, the voxel structure is used to store the illumination information of a simplified scene, and the indirect illumination effects can be obtained by collecting the illumination information using the voxel cone tracing method. Only the voxel structure of the dynamic scene is updated in each frame, which supports dynamic light sources and avoids unnecessary calculations for updating the static scene. The voxel structure is a directional hierarchical structure generated by anisotropic filtering, which can be compressed and stored in a mipmapped three-dimensional texture, reducing the storage costs. It is possible to calculate the global illumination effects, such as ambient occlusion and soft shadow, by collecting the outgoing radiance and occlusion values stored in the voxel structure using the voxel cone tracing method. The experimental results demonstrate that this approach can obtain various global illumination effects and exhibit a decent rendering efficiency. Furthermore, the single-frame time is less than 33.3 ms in case of complex scenes.
引文
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[19] Sugihara M,Rauwendaal R,Salvi M.Layered reflective shadow maps for voxel-based indirect illumination[C]//Proceedings of High Performance Graphics,June 23-25,2014,Lyon,France.Switzerland:Eurographics Association Aire-la-Ville,2014:117-125.
[20] Chen Y Y,Chien S Y.Lighting-driven voxels for memory-efficient computation of indirect illumination[J].The Visual Computer,2016,32(6/7/8):781-789.
[21] Li H,Yang H M,Zhao J P,et al.Hybrid-resolution shadow mapping design and hard shadows anti-aliasing in special effects movies[J].Chinese Optics,2016,9(1):89-96.李华,杨华民,赵建平,等.特效电影工程中混合分辨率阴影图设计与硬阴影反走样[J].中国光学,2016,9(1):89-96.
[2] Wu K W,Yang X Z,Xie Z.Regional-oriented non-uniform illumination estimation[J].Acta Optica Sinica,2016,36(2):0233001.吴克伟,杨学志,谢昭.面向区域的非均匀光照估计方法[J].光学学报,2016,36(2):0233001.
[3] Cui S,Zhang J,Gao J.Illumination estimation based on exemplar learning in logarithm domain[J].Acta Optica Sinica,2018,38(2):0233001.崔帅,张骏,高隽.对数域中基于实例学习的光照估计[J].光学学报,2018,38(2):0233001.
[4] Yang Z H,Wei L,Zhang Q Q,et al.Ray-tracing algorithm of elliptical reflection zone plate[J].Acta Optica Sinica,2017,37(9):0920001.杨祖华,魏来,张强强,等.椭圆反射式波带片光线追迹算法[J].光学学报,2017,37(9):0920001.
[5] Yuan Y W,Quan J C,Wu C,et al.Ray tracing acceleration structure based on octree adaptive volume merging[J].Acta Optica Sinica,2017,37(1):0120001.袁昱纬,全吉成,吴晨,等.基于八叉树自适应体归并的光线跟踪加速结构[J].光学学报,2017,37(1):0120001.
[6] Huang K,Cheng X J,Jia D F,et al.An automatic segmentation algorithm for dense pipeline point cloud data[J].Chinese Journal of Lasers,2018,45(11):1104004.黄凯,程效军,贾东峰,等.一种密集管道点云数据自动分割算法[J].中国激光,2018,45(11):1104004.
[7] Wehr D,Radkowski R.Parallel kd-tree construction on the GPU with an adaptive split and sort strategy[J].International Journal of Parallel Programming,2018,46(6):1139-1156.
[8] Mara M,Mcguire M,Bitterli B,et al.An efficient denoising algorithm for global illumination[C]∥Proceedings of High Performance Graphics,July 28-30,2017,Los Angeles,California.New York:ACM,2017:3.
[9] Li M L,Zong W P,Li G Y,et al.Extraction of structure line segments from point clouds using voxel-based region growing[J].Acta Optica Sinica,2018,38(1):0112001.李明磊,宗文鹏,李广云,等.基于体素生长的点云结构直线段提取[J].光学学报,2018,38(1):0112001.
[10] Laine S,Karras T.Efficient sparse voxel octrees[J].IEEE Transactions on Visualization and Computer Graphics,2011,17(8):1048-1059.
[11] K?mpe V,Sintorn E,Assarsson U.High resolution sparse voxel DAGs[J].ACM Transactions on Graphics,2013,32(4):101.
[12] Yuan Y W,Quan J C,Wu C,et al.Illumination-computation acceleration structure based on sparse voxel directed acyclic graph[J].Acta Optica Sinica,2017,37(8):0820001.袁昱纬,全吉成,吴晨,等.基于稀疏体素有向无环图的光照计算加速结构[J].光学学报,2017,37(8):0820001.
[13] Villanueva A J,Marton F,Gobbetti E.Symmetry-aware sparse voxel dags (SSVDAGs) for compression-domain tracing of high-resolution geometric scenes[J].Journal of Computer Graphics Techniques,2017,6(2):1-30.
[14] Zhang Y M,Garcia S,Xu W W,et al.Efficient voxelization using projected optimal scanline[J].Graphical Models,2018,100:61-70.
[15] Ren G Y,Lü X Q,Yang N,et al.Application of improved voxels growth algorithm in cardiac local vascular extraction[J].Laser & Optoelectronics Progress,2018,55(6):061701.任国印,吕晓琪,杨楠,等.改进的体素生长算法在心脏局部血管提取中的应用[J].激光与光电子学进展,2018,55(6):061701.
[16] Kaplanyan A.Cascaded light propagation volumes for real-time indirect illumination[C]∥Proceedings of the 2010 ACM SIGGRAPH Symposium on Interactive 3D Graphics & Games,February 19-21,2010,Washington,D.C.New York:ACM,2010:99-107.
[17] Crassin C,Neyret F,Sainz M,et al.Interactive indirect illumination using voxel cone tracing[J].Computer Graphics Forum,2011,30(7):1921-1930.
[18] Franke T A.Delta voxel cone tracing[C]∥2014 IEEE International Symposium on Mixed and Augmented Reality (ISMAR),September 10-12,2014,Munich,Germany.New York:IEEE,2014:39-44.
[19] Sugihara M,Rauwendaal R,Salvi M.Layered reflective shadow maps for voxel-based indirect illumination[C]//Proceedings of High Performance Graphics,June 23-25,2014,Lyon,France.Switzerland:Eurographics Association Aire-la-Ville,2014:117-125.
[20] Chen Y Y,Chien S Y.Lighting-driven voxels for memory-efficient computation of indirect illumination[J].The Visual Computer,2016,32(6/7/8):781-789.
[21] Li H,Yang H M,Zhao J P,et al.Hybrid-resolution shadow mapping design and hard shadows anti-aliasing in special effects movies[J].Chinese Optics,2016,9(1):89-96.李华,杨华民,赵建平,等.特效电影工程中混合分辨率阴影图设计与硬阴影反走样[J].中国光学,2016,9(1):89-96.