Path cuts

In scenes lit with sharp point-like light sources, light can bounce several times on specular materials before getting into our eyes, forming purely specular light paths. However, to our knowledge, rendering such multi-bounce pure specular paths has not been handled in previous work: while many light transport methods have been devised to sample various kinds of light paths, none of them are able to find multi-bounce pure specular light paths from a point light to a pinhole camera. In this paper, we present path cuts to efficiently render such light paths. We use a path space hierarchy combined with interval arithmetic bounds to prune non-contributing regions of path space, and to slice the path space into regions small enough to empirically contain at most one solution. Next, we use an automatic differentiation tool and a Newton-based solver to find an admissible specular path within a given path space region. We demonstrate results on several complex specular configurations, including RR, TT, TRT and TTTT paths.

[1]  Steve Marschner,et al.  Microfacet Models for Refraction through Rough Surfaces , 2007, Rendering Techniques.

[2]  Steve Marschner,et al.  Rendering specular microgeometry with wave optics , 2018, ACM Trans. Graph..

[3]  Shuang Zhao,et al.  Single scattering in refractive media with triangle mesh boundaries , 2009, SIGGRAPH '09.

[4]  K. Bala,et al.  Multidimensional lightcuts , 2006, SIGGRAPH 2006.

[5]  Adam Arbree,et al.  To appear in the ACM SIGGRAPH conference proceedings Lightcuts: A Scalable Approach to Illumination , 2022 .

[6]  Shuang Zhao,et al.  Automatic bounding of programmable shaders for efficient global illumination , 2009, SIGGRAPH 2009.

[7]  K. Bala,et al.  Lightcuts: a scalable approach to illumination , 2005, SIGGRAPH 2005.

[8]  BENEDIKT BITTERLI,et al.  Selectively metropolised Monte Carlo light transport simulation , 2019, ACM Trans. Graph..

[9]  Pat Hanrahan,et al.  Illumination from curved reflectors , 1992, SIGGRAPH.

[10]  Steve Marschner,et al.  Learning generative models for rendering specular microgeometry , 2019, ACM Trans. Graph..

[11]  HanikaJohannes,et al.  Improved Half Vector Space Light Transport , 2015 .

[12]  Luca Fascione,et al.  Manifold Next Event Estimation , 2015, Comput. Graph. Forum.

[13]  Anton Kaplanyan,et al.  Improved Half Vector Space Light Transport , 2015, Comput. Graph. Forum.

[14]  Steve Marschner,et al.  Manifold exploration , 2012, ACM Trans. Graph..

[15]  Rudolf Krawczyk,et al.  Newton-Algorithmen zur Bestimmung von Nullstellen mit Fehlerschranken , 1969, Computing.

[16]  Steve Marschner,et al.  Discrete stochastic microfacet models , 2014, ACM Trans. Graph..

[17]  Leonidas J. Guibas,et al.  Robust Monte Carlo methods for light transport simulation , 1997 .

[18]  Anton Kaplanyan,et al.  Path Space Regularization for Holistic and Robust Light Transport , 2013, Comput. Graph. Forum.

[19]  Nicolas Holzschuch,et al.  Accurate Computation of Single Scattering in Participating Media with Refractive Boundaries , 2015, Comput. Graph. Forum.

[20]  Wenzel Jakob,et al.  Specular manifold sampling for rendering high-frequency caustics and glints , 2020, ACM Trans. Graph..

[21]  K. Bala,et al.  Single scattering in refractive media with triangle mesh boundaries , 2009, SIGGRAPH 2009.

[22]  Steve Marschner,et al.  Rendering glints on high-resolution normal-mapped specular surfaces , 2014, ACM Trans. Graph..

[23]  Anton Kaplanyan,et al.  The natural-constraint representation of the path space for efficient light transport simulation , 2014, ACM Trans. Graph..

[24]  HanrahanPat,et al.  Illumination from curved reflectors , 1992 .

[25]  Shuang Zhao,et al.  Automatic bounding of programmable shaders for efficient global illumination , 2009, ACM Trans. Graph..

[26]  Steve Marschner,et al.  Position-normal distributions for efficient rendering of specular microstructure , 2016, ACM Trans. Graph..