guiding indirect illumination - univerzita karlovajirka/path-guiding-in-production/2019/... ·...
TRANSCRIPT
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
JIŘÍ VORBAWETA DIGITAL
GUIDING INDIRECT ILLUMINATION
Alita: Battle Angel |© 2018 Twentieth Century Fox Film Corporation
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
GUIDED DIRECTIONAL SAMPLING
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Jensen [1995]
HISTORY
• Lafortune and Willems [1995]
Learning from photons Learning from forward samples
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Jensen [1995]
HISTORY
• Lafortune and Willems [1995]
Learning from photons Learning from forward samples
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Jensen [1995]
HISTORY
• Lafortune and Willems [1995]
Learning from photons Learning from forward samples
![Page 6: GUIDING INDIRECT ILLUMINATION - Univerzita Karlovajirka/path-guiding-in-production/2019/... · JiříVorba | Path Guiding in Production - Introduction WETA DIGITAL LTD.2019 • Jensen](https://reader036.vdocuments.mx/reader036/viewer/2022070812/5f0bd3b97e708231d4326819/html5/thumbnails/6.jpg)
Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Jensen [1995]
HISTORY
• Lafortune and Willems [1995]
Learning from photons Learning from forward samples
![Page 7: GUIDING INDIRECT ILLUMINATION - Univerzita Karlovajirka/path-guiding-in-production/2019/... · JiříVorba | Path Guiding in Production - Introduction WETA DIGITAL LTD.2019 • Jensen](https://reader036.vdocuments.mx/reader036/viewer/2022070812/5f0bd3b97e708231d4326819/html5/thumbnails/7.jpg)
Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Jensen [1995]
• Hey and Purgathofer [2002]
• Vorba et al. [2014]
• Herholz et al. [2016, 2019]
HISTORY
• Lafortune and Willems [1995]
• Pegoraro et al. [2008]
• Bashford-Rogers et al. [2012]
• Müller et al. [2017]
• Dahm and Keller [2018]
• Simon et al. [2018]
Learning from photons Learning from forward samples
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
2D DIRECTIONAL MODELSHey and Purgathofer [2002](Kernel density)
Jensen [1995](Histograms)
Vorba et al. [2014](Gaussian mixtures)
41
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• How to learn from samples?
– Preprocess, interleaved tracing
• How to represent the knowledge?
– Mixtures of Gaussians cached in the scene
• How to exploit it in the simulation?
– Fetch nearest mixture
Preprocess Rendering
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
The BFG|© 2016 Storyteller Distribution Co., LLC.
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
The BFG|© 2016 Storyteller Distribution Co., LLC.
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
The BFG|© 2016 Storyteller Distribution Co., LLC.
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
Guided Russian roulette and splitting
OPTIMAL PATH LENGTH
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Importance sampling of path length
• Splitting when expected contribution is high
• Vorba et Křivánek [2016]
GUIDED RUSSIAN ROULETTE AND SPLITTING
subsurface
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Termination probability
ALBEDO BASED RUSSIAN ROULETTE
[Arvo & Kirk 1990]
Current path weight
User given threshold
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Termination probability
ALBEDO BASED RUSSIAN ROULETTE
[Arvo & Kirk 1990]
[Jensen 2001]
Current path weight
Albedo
User given threshold
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Termination probability
• Problem: it’s local
• Kill paths too early
• Waste time on long paths
ALBEDO BASED RUSSIAN ROULETTE
[Arvo & Kirk 1990]
[Jensen 2001]
Current path weight
Albedo
User given threshold
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Input
– approximation of radiance field
– estimate of pixel values
• Output
– Termination probability / path split ratio
GUIDED RUSSIAN ROULETTE AND SPLITTING
Expected path contribution
(given current vertices)
Pixel estimate[Vorba a Křivánek 2016]
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Path tracing (1h)
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Path tracing (1h) Guided RR and splitting (1h)
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Path tracing (1h) Guided RR and splitting (1h)
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Path tracing (1h)
Guided RR and splitting (1h)
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Path tracing (1h)
57
Guided RR and splitting + Directional guiding (1h)
Guided RR and splitting (1h)
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
PIXEL VALUE ESTIMATES (Vorba et Křivánek [2016])
Estimate Reference
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Can be simplified in practice
• Many possible approaches (low sample count -> denoising)
• MIP mapping of beauty image (at Weta)
PIXEL VALUE ESTIMATES (progressive rendering)
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Minimal overhead
• Makes guiding cheap
• Better results than each method alone
SYNERGY
Directional guiding
Guided RR and splitting
+
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
• Path guiding as adaptive sampling in path space
• Guide all the decisions
– Guided directional sampling
– Guided Russian roulette and splitting (Path length)
– Guided light sampling (Next-event estimation)
– Guided free flight (Ray-distance sampling)
Summary
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Jiří Vorba | Path Guiding in Production - IntroductionWETA DIGITAL LTD.2019
THANK YOU
The BFG|© 2016 Storyteller Distribution Co., LLC.
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Alita: Battle Angel |© 2018 Twentieth Century Fox Film Corporation
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Wednesday, 31 July, 9:30am - 6pm
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Jiří Vorba | Path Guiding in ProductionWETA DIGITAL LTD.2019