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Received：06 December 2021，
Revised：2022-1-19，
Accepted：26 January 2022，
Published：16 February 2023
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目的
2
在实时渲染领域中，立即辐射度算法是用于实时模拟间接光泽反射效果的算法之一。基于立即辐射度的GGX SLC（stochastic light culling）算法中使用符合真实物理定律的GGX BRDF（bidirectional reflectance distribution function）光照模型计算间接光泽反射，计算复杂度很高，并且其计算开销会随着虚拟点光源的数量呈明显的线性增长。为解决上述问题，提出一种更高效的实时间接光泽反射渲染算法。
方法
2
基于数学方法中的线性变换球面分布，将计算复杂度很高的GGX BRDF球面分布近似为一种计算复杂度较低的球面分布，并基于该球面分布提出了在单点光源以及多点光源环境下的基于物理的快速光照模型。该光照模型相比GGX BRDF光照模型具有更低的计算开销。然后基于该光照模型，提出实时间接光泽反射渲染算法，计算虚拟点光源对着色点的辐射强度，结合多点光源光照模型对着色点着色，高效地渲染间接光泽反射效果。
结果
2
实验结果表明，改进后的实时间接光泽反射算法能够以更高的渲染效率实现与GGX SLC算法相似的渲染效果，渲染效率提升了20%~40%，并且场景中虚拟点光源数量越多，所提算法的效率提升越大。
结论
2
基于线性变换球面分布的实时间接光泽反射算法，相比于GGX SLC算法，能够在不降低渲染效果的基础上，大幅提升间接光泽反射的渲染效率。
Objective
2
Indirect glossy reflection effect (IGRE) can be as one of the commonly-used lighting effects nowadays. The IGRE-based simulation has been developing in related to designs of games
movies
animations
virtual reality and visual simulation. The IGRE can be employed to enhance image quality and is an essential part of the rendering in computer graphics. Current instant radiosity (IR) algorithm is beneficial to IGRE for real-time rendering. In order to calculate the glossy reflection effect (GRE) at the virtual point lights and the shading points
a certain lighting model is usually adopted to calculate the radiance of the ray-reflected like Blinn-Phong lighting model. In recent years
to calculate the IGR
IR-based GGX stochastic light culling algorithm (SLC) is focused on the GGX bidirectional reflectance distribution function (BRDF) lighting model further. However
the GGX BRDF lighting model has featured of high computational complexity
and it is time-consuming as well
including redundant trigonometric functions and square roots. Meanwhile
its computational overhead will increase dramatically in linear with the growth of the number of virtual point lights. To optimize the IGR effects
there are often hundreds of thousands or even millions of virtual point lights in the scene
which will cause very high shading overhead in the GGX SLC algorithm. But
the rendering performance is still ultimately challenged. So
we focus on the GGX SLC algorithm and carry out the analysis of the high overhead caused by the GGX SLC algorithm
which uses the GGX BRDF lighting model when rendering the IGR in detail. Our method is developed to improve the real-time IGR algorithm in terms of IR (i.e. GGX SLC algorithm).
Method
2
To lower the computational complexity of GGX BRDF spherical distribution
our research is concerned of the mutual-fitted issue of GGX BRDF spherical distribution with another spherical distribution based on linearly transformed spherical distribution. In this way
the goal of the GGX BRDF-simplified can be achieved. This spherical distribution to low computational complexity is melted into the point light source and a fast physics-based lighting model is obtained from single-point and multi-point light sources. This lighting model has a lower computational cost compared to the GGX BRDF lighting model. First
this fast lighting model is used to calculate the radiance of the virtual point lights and the shading points both. To improve its rendering efficiency
we implement a lighting model-based texture sampling strategy. Our algorithm has its potentials to improve the rendering efficiency of the indirect glossy reflection effect without the rendering quality loss.
Result
2
We conduct several experiments to verify that our real-time indirect glossy reflection algorithm. First
to validate the feasibility of our lighting model
our lighting model is compared to the GGX BRDF lighting model. The root mean squared error (RMSE) of our algorithm is less than 0.002. This indicates that our lighting model can achieve similar rendering quality to the GGX BRDF lighting model. Next
our algorithm is optimized and linked to improve rendering quality and rendering efficiency in different scenes. Our experiment results show that our rendering quality is very close to the GGX SLC algorithm (the RMSE is less than 0.006). The rendering efficiency can be increased up to 40% in the Sponza scene. The experiments are carried out on the effectiveness of the number of virtual point lights between the two algorithms mentioned above. The experimental results demonstrate that the efficiency of our algorithm can be improved more based on the number of virtual point lights-enlarged in the scene
while little loss in rendering quality compared with the GGX SLC algorithm. The RMSE is less than 0.003 while the rendering efficiency improvement can reach 30% in the metal ring scene.
Conclusion
2
A real-time indirect glossy reflection algorithm is developed in terms of linearly transformed spherical distribution. A lighting model with lower computational complexity is employed to optimize the GGX BRDF lighting model
which can reduce rendering overhead better. To alleviate the problem of texture sampling
a texture sampling scheme is optimized to improve rendering efficiency further. The experiment results demonstrate that our algorithm can improve the rendering efficiency of the indirect glossy reflection effect without sacrifice rendering quality potentially.
Balestra C. 2008. The technology of uncharted: drake's fortune [EB/OL]. [2021-02-22] . https://www.gdcvault.com/play/325/The-Technology-of-UNCHARTED-DRAKE https://www.gdcvault.com/play/325/The-Technology-of-UNCHARTED-DRAKE
Beckmann P and Spizzichino A. 1987. The Scattering of Electromagnetic Waves from Rough Surfaces. Dedham: Artech House
Cook R L and Torrance K E. 1982. A reflectance model for computer graphics. ACM Transactions on Graphics, 1(1): 7-24 [DOI: 10.1145/357290.357293]
Dachsbacher C, Křivánek J, Hašan M, Arbree A, Walter B and Novák J. 2014. Scalable realistic rendering with many-light methods. Computer Graphics Forum, 33(1): 88-104 [DOI: 10.1111/cgf.12256]
Dachsbacher C and Stamminger M. 2005. Reflective shadow maps//2005 Symposium on Interactive 3D Graphics and Games. Washington District of Columbia, USA: Association for Computing Machinery: 203-231 [ DOI: 10.1145/1053427.1053460 http://dx.doi.org/10.1145/1053427.1053460 ]
Dachsbacher C and Stamminger M. 2006. Splatting indirect illumination//2006 Symposium on Interactive 3D Graphics and Games. Redwood City, USA: Association for Computing Machinery: 93-100 [ DOI: 10.1145/1111411.1111428 http://dx.doi.org/10.1145/1111411.1111428 ]
Diolatzis S, Gruson A, Jakob W, Nowrouzezahrai D and Drettakis G. 2020. Practical product path guiding using linearly transformed cosines. Computer Graphics Forum, 39(4): 23-33 [DOI: 10.1111/cgf.14051]
Estevez A C and Kulla C. 2018. Importance sampling of many lights with adaptive tree splitting. Proceedings of the ACM on Computer Graphics and Interactive Techniques, 1(2): #25 [DOI: 10.1145/3233305]
Faure W and Chang C F. 2010. Metalights: improved interleaved shading. Computer Graphics Forum, 29(7): 2109-2117 [DOI: 10.1111/j.1467-8659.2010.01798.x]
Heitz E, Dupuy J, Hill S and Neubelt D. 2016. Real-time polygonal-light shading with linearly transformed cosines. ACM Transactions on Graphics, 35(4): #41 [DOI: 10.1145/2897824.2925895]
Keller A. 1997. Instant radiosity//Proceedings of the 24th Annual Conference on Computer Graphics and Interactive Techniques. [s. l.]: ACM Press/Addison-Wesley Publishing Co. : 49-56 [ DOI: 10.1145/258734.258769 http://dx.doi.org/10.1145/258734.258769 ]
Lagarde S and De Rousiers C. 2014. Moving frostbite to PBR [EB/OL]. [2021-08-13] . https://media.contentapi.ea.com/content/dam/eacom/frostbite/files/s2014-pbs-frostbite-slides.pdf https://media.contentapi.ea.com/content/dam/eacom/frostbite/files/s2014-pbs-frostbite-slides.pdf
Li T M, Aittala M, Durand F and Lehtinen J. 2018. Differentiable Monte Carlo ray tracing through edge sampling. ACM Transactions on Graphics, 37(6): #222 [DOI: 10.1145/3272127.3275109]
LinD Q and Yuksel C. 2020. Real-time stochastic lightcuts. Proceedings of the ACM on Computer Graphics and Interactive Techniques, 3(1): #5 [DOI: 10.1145/3384543]
Luksch C, Prost L and Wimmer M. 2020. Real-time approximation of photometric polygonal lights. Proceedings of the ACM on Computer Graphics and Interactive Techniques, 3(1): #4 [DOI: 10.1145/3384537]
Luksch C, Wimmer M and Schwärzler M. 2019. Incrementally baked global illumination//The ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games. Montreal, Canada: Association for Computing Machinery: #4 [ DOI: 10.1145/3306131.3317015 http://dx.doi.org/10.1145/3306131.3317015 ]
McAuley S, Hill S, Hoffman N, Gotanda Y, Smits B, Burley B and Martinez A. 2012. Practical physically-based shading in film and game production//ACM SIGGRAPH 2012 Courses, New York, USA: ACM: 1-7 [ DOI: 10.1145/2343483.2343493 http://dx.doi.org/10.1145/2343483.2343493 ]
Moreau P and Clarberg P. 2019. Importance sampling of many lights on the GPU//Ray Tracing Gems. Berkeley, CA: Apress: 255-283 [ DOI: 10.1007/978-1-4842-4427-2_18 http://dx.doi.org/10.1007/978-1-4842-4427-2_18 ]
Olsson O, Billeter M and Assarsson U. 2012. Clustered deferred and forward shading//Proceedings of the 4th ACM SIGGRAPH/Eurographics Conference on High-Performance Graphics. Paris, France: The Eurographics Association: 87-96 [ DOI: 10.2312/EGGH/HPG12/087-096 http://dx.doi.org/10.2312/EGGH/HPG12/087-096 ]
Phong B T. 1975. Illumination for computer generated pictures. Communications of the ACM, 18(6): 311-317 [DOI: 10.1145/360825.360839]
Segovia B, Iehl J C, Mitanchey R and Péroche B. 2006. Non-interleaved deferred shading of interleaved sample patterns//The 21st ACM SIGGRAPH/EUROGRAPHICS Symposium on Graphics Hardware. Vienna, Austria: Association for Computing Machinery: 53-60 [ DOI: 10.1145/1283900.1283909 http://dx.doi.org/10.1145/1283900.1283909 ]
Tokuyoshi Y and Harada T. 2016. Stochastic light culling. Journal of Computer Graphics Techniques, 5(1): 35-60
Tokuyoshi Y and Harada T. 2017. Stochastic light culling for VPLs on GGX microsurfaces. Computer Graphics Forum, 36(4): 55-63 [DOI: 10.1111/cgf.13224]
Vévoda P, Kondapaneni I and Křivánek J. 2018. Bayesian online regression for adaptive direct illumination sampling. ACM Transactions on Graphics, 37(4): #125 [DOI: 10.1145/3197517.3201340]
Walter B, Arbree A, Bala K and Greenberg D P. 2006. Multidimensional lightcuts//Proceedings of ACM SIGGRAPH 2006 Papers. Boston, USA: Association for Computing Machinery: 1081-1088 [ DOI: 10.1145/1179352.1141997 http://dx.doi.org/10.1145/1179352.1141997 ]
Walter B, Fernandez S, Arbree A, Bala K, Donikian M and Greenberg D P. 2005. Lightcuts: a scalable approach to illumination//Proceedings of ACM SIGGRAPH 2005 Papers. Los Angeles, USA: Association for Computing Machinery: 1098-1107 [ DOI: 10.1145/1186822.1073318 http://dx.doi.org/10.1145/1186822.1073318 ]
Walter B, Khungurn P and Bala K. 2012. Bidirectional lightcuts. ACM Transactions on Graphics, 31(4): #59 [DOI: 10.1145/2185520.2185555]
Walter B, Marschner S R, Li H S and Torrance K E. 2007. Microfacet models for refraction through rough surfaces//Proceedings of the 18th Eurographics Conference on Rendering Techniques. Grenoble, France: Eurographics Association: 195-206
Wang L L, Li R Z, Shi X H, Yan L Q and Li Z C. 2020. Foveated instant radiosity//2020 IEEE International Symposium on Mixed and Augmented Reality (ISMAR). Porto de Galinhas, Brazil: IEEE: 1-11 [ DOI: 10.1109/ISMAR50242.2020.00017 http://dx.doi.org/10.1109/ISMAR50242.2020.00017 ]
Yuksel C. 2019. Stochastic lightcuts//Proceedings of 2019 Conference on High-Performance Graphics. Strasbourg, France: The Eurographics Association: 27-32 [ DOI: 10.2312/hpg.20191192 http://dx.doi.org/10.2312/hpg.20191192 ]
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