Radiance Caching for Efficient Global Illumination Computation

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Radiance Caching for Efficient Global
Illumination Computation

• J. Krivánek P. Gautron
• S. Pattanaik K. Bouatouch

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High Quality GI
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Global Illumination How?
Lo(P, ?o)
BRDF(?o, ?i) cos(?)d?i
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Monte Carlo
Lo(P, ?o)
BRDF(?o, ?i) cos(?)d?i
No analytical solution
Shooting
Gathering
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Shooting
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Shooting
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Shooting
Final gathering costly
Photon map only for indirect diffuse
Distribution ray tracing for non diffuse noisy
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Gathering
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Gathering
Support for glossy GI
Random sampling noisy
High quality many rays
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Irradiance Caching
Sparse computation of indirect diffuse lighting
?
?
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Irradiance Caching
Sparse computation of indirect diffuse lighting
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Irradiance Caching
Sparse computation of indirect diffuse lighting
Interpolation
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Gradients
Why?
Without gradients
With gradients
Images from "Irradiance Gradients", Gregory J.
Ward, Paul S. Heckbert Eurographics Workshop on R
endering 1992
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Gradients
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Rotational gradient
?
E Ei
E Ei

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Translational gradient
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Non diffuse surfaces
Irradiance values indirect diffuse
Indirect glossy distribution ray tracing
High quality many rays
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Contributions
Extension to indirect glossy lighting
BDRF-based selection of record points
Low frequency records
High frequency distribution ray tracing
Novel translational gradient
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Caching on glossy surfaces
Need hemispherical data representation
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Caching on glossy surfaces
?
Need new gradients
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Hemispherical Functions
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Original Function
Piecewise linear approximation
Need a more compact and smooth representation
Better fitting
Fast computation of integrals
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Orthogonal Polynomials
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Application to GI
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Incident Radiance
BRDF
? dot product
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Spherical Harmonics
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Hemispherical Harmonics
A Novel Hemispherical Basis for Accurate and
Efficient Rendering P. Gautron, J. Krivànek, S. P
attanaik, K. Bouatouch, EGSR 04
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Why (Hemi)Spherical harmonics?
Ease of use
Rotation support
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Representation Limitations
Bandlimited "ringing" artifacts
Limit to low-frequency BRDFs
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Adaptive BRDF Representation
Why?
Low frequency "(H)SH-Friendly"
High frequency
Ward BRDF with same parameters
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Adaptive BRDF Representation
How?
BRDF 4D Function
Parabolic Parameterization
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Incoming Radiance
Same principle as Irradiance Caching
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Incoming Radiance
Same principle as Irradiance Caching
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Radiance Gradients
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Rotational gradient
Rotation Matrix
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Translational gradient
Goal
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Translational Gradient
Numerical Method
p
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Translational Gradient
Numerical Method
p
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Translational Gradient
Numerical Method
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Translational Gradient
Analytical Method
Li (?k, Fk)
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Outgoing Radiance
Ri

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Outgoing Radiance
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Outgoing Radiance
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Incident Radiance
BRDF
? dot product
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Stills comparison
Monte Carlo Path Tracing
Radiance Caching
Rendering time 155s
P4 2.2GHz, 512MB RAM
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Stills comparison
Monte Carlo Path Tracing
Radiance Caching
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Video Cornell Box
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Video Flamingo
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Outline
Introduction
IC for glossy surfaces
Hemispherical data representation
Radiance gradients
Outgoing radiance computation
Results
Conclusion
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Conclusion
Extension of irradiance caching to radiance
caching
Definition of new translational gradient
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Future Work
"All-frequency" hemispherical representation
Hardware support
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Any Questions ?
Rendered using Radiance Caching