Radiance Caching for Efficient Global Illumination

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Radiance Caching for Efficient Global Illumination Computation: 

Radiance Caching for Efficient Global Illumination Computation J. Křivánek P. Gautron S. Pattanaik K. Bouatouch

High Quality GI: 

High Quality GI

Global Illumination… How?: 

Global Illumination… How? Lo(P, ωo) * BRDF(ωo, ωi) *cos(θ)dωi

Monte Carlo: 

Monte Carlo Shooting Gathering Lo(P, ωo) * BRDF(ωo, ωi) *cos(θ)dωi No analytical solution

Shooting: 

Shooting

Shooting: 

Shooting

Shooting: 

Shooting Final gathering: costly Photon map only for indirect diffuse Distribution ray tracing for non diffuse: noisy

Gathering: 

Gathering

Gathering: 

Gathering Random sampling: noisy High quality: many rays Support for glossy GI

Irradiance Caching: 

Irradiance Caching   Sparse computation of indirect diffuse lighting

Irradiance Caching: 

Irradiance Caching Sparse computation of indirect diffuse lighting

Irradiance Caching: 

Irradiance Caching Interpolation Sparse computation of indirect diffuse lighting

Gradients: 

Gradients Why? Without gradients With gradients Images from "Irradiance Gradients", Gregory J. Ward, Paul S. Heckbert Eurographics Workshop on Rendering 1992

Gradients: 

Gradients

Rotational gradient: 

Rotational gradient θ E = Ei E = Ei + …

Translational gradient: 

Translational gradient

Non diffuse surfaces: 

Non diffuse surfaces Indirect glossy: distribution ray tracing High quality: many rays Irradiance values: indirect diffuse

Contributions: 

Contributions BDRF-based selection of record points Novel translational gradient Extension to indirect glossy lighting Low frequency: records High frequency: distribution ray tracing

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Caching on glossy surfaces: 

Caching on glossy surfaces Need hemispherical data representation

Caching on glossy surfaces: 

Caching on glossy surfaces ? Need new gradients

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Hemispherical Functions: 

Hemispherical Functions Original Function Piecewise linear approximation  Need a more compact and smooth representation Better fitting Fast computation of integrals

Orthogonal Polynomials: 

Orthogonal Polynomials

Application to GI: 

Application to GI Incident Radiance BRDF  dot product 

Spherical Harmonics: 

Spherical Harmonics

Hemispherical Harmonics: 

Hemispherical Harmonics A Novel Hemispherical Basis for Accurate and Efficient Rendering P. Gautron, J. Křivànek, S. Pattanaik, K. Bouatouch, EGSR 04

Why (Hemi)Spherical harmonics?: 

Why (Hemi)Spherical harmonics? Ease of use Rotation support

Representation Limitations: 

Representation Limitations Bandlimited: "ringing" artifacts Limit to low-frequency BRDFs

Adaptive BRDF Representation: 

Adaptive BRDF Representation Low frequency "(H)SH-Friendly" High frequency Why? Ward BRDF with same parameters

Adaptive BRDF Representation: 

Adaptive BRDF Representation How? BRDF = 4D Function Parabolic Parameterization

Incoming Radiance: 

Incoming Radiance Same principle as Irradiance Caching

Incoming Radiance: 

Incoming Radiance Same principle as Irradiance Caching

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Radiance Gradients: 

Radiance Gradients

Rotational gradient: 

Rotational gradient Rotation Matrix

Translational gradient: 

Translational gradient Goal

Translational Gradient: 

Translational Gradient Numerical Method p

Translational Gradient: 

Translational Gradient Numerical Method p

Translational Gradient: 

Translational Gradient Numerical Method

Translational Gradient: 

Translational Gradient Analytical Method Li (θk, Φk)*

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Outgoing Radiance: 

Outgoing Radiance Ri =

Outgoing Radiance: 

Outgoing Radiance

Outgoing Radiance: 

Outgoing Radiance Incident Radiance BRDF  dot product 

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Stills comparison: 

Stills comparison P4 2.2GHz, 512MB RAM Monte Carlo Path Tracing Radiance Caching Rendering time: 155s

Stills comparison: 

Stills comparison Monte Carlo Path Tracing Radiance Caching

Video: Cornell Box: 

Video: Cornell Box

Video: Flamingo: 

Video: Flamingo

Outline: 

Outline Introduction IC for glossy surfaces Hemispherical data representation Radiance gradients Outgoing radiance computation Results Conclusion

Conclusion: 

Conclusion Extension of irradiance caching to radiance caching Definition of new translational gradient

Future Work: 

Future Work "All-frequency" hemispherical representation Hardware support

Any Questions ?: 

Any Questions ? Rendered using Radiance Caching