Title
Volume Path Guiding Based on Zero-Variance Random Walk Theory
Abstract
The efficiency of Monte Carlo methods, commonly used to render participating media, is directly linked to the manner in which random sampling decisions are made during path construction. Notably, path construction is influenced by scattering direction and distance sampling, Russian roulette, and splitting strategies. We present a consistent suite of volumetric path construction techniques where all these sampling decisions are guided by a cached estimate of the adjoint transport solution. The proposed strategy is based on the theory of zero-variance path sampling schemes, accounting for the spatial and directional variation in volumetric transport. Our key technical contribution, enabling the use of this approach in the context of volume light transport, is a novel guiding strategy for sampling the particle collision distance proportionally to the product of transmittance and the adjoint transport solution (e.g., in-scattered radiance). Furthermore, scattering directions are likewise sampled according to the product of the phase function and the incident radiance estimate. Combined with guided Russian roulette and splitting strategies tailored to volumes, we demonstrate about an order-of-magnitude error reduction compared to standard unidirectional methods. Consequently, our approach can render scenes otherwise intractable for such methods, while still retaining their simplicity (compared to, e.g., bidirectional methods).
Year
DOI
Venue
2019
10.1145/3230635
ACM Transactions on Graphics (TOG)
Keywords
Field
DocType
Monte Carlo, importance sampling, participating media rendering, path guiding, volume light transport, zero variance path sampling theory
Importance sampling,Mathematical optimization,Monte Carlo method,Random walk,Distance sampling,Collision,Sampling (statistics),Roulette,Mathematics,Radiance
Journal
Volume
Issue
ISSN
38
3
0730-0301
Citations 
PageRank 
References 
0
0.34
0
Authors
6
Name
Order
Citations
PageRank
Sebastian Herholz1115.13
Yangyang Zhao2529.46
Oskar Elek3324.33
Derek Nowrouzezahrai480154.49
Hendrik P. A. Lensch5147196.59
Jaroslav Krivánek629021.61