Accurate Image Based Relighting through Optimization Pieter Peers
Accurate Image Based Relighting through Optimization Pieter Peers Philip Dutré Department of Computer Science K. U. Leuven, Belgium
What is Image Based Relighting? Basis Images Relit Image Processing & Relighting
Previous Work • The Light Stage (Debevec et al. ’ 00) Images: ACM SIGGRAPH ‘ 00
Previous Work • Environment Matting (Zonker et al. ’ 99, Chuang et al. ’ 00) Images: ACM SIGGRAPH ’ 99
Previous work Diffuse Materials Specular Materials + - Sufficient angular sampling Sparse sampling of light source directions - + The Light Stage Environment Matting Large span of incoming light directions • Matusik et al. EGWR’ 02 Bundled incoming light directions
Three-step algorithm 2 1 Basis Image Recording 3 Relit image = Captured reflectance + Light-map Reflectance field calculation
Basis Image Recording
Basis Image Recording
Basis Image Recording . . . HDR photographs
Practical Setup • HDR photographs • Monitor calibration • 4 x 4 grid, 9 patterns per lightpatch • ± 600 basis images
Three-step algorithm 2 1 Basis Image Recording 3 Relit image = Captured reflectance + Light-map Reflectance field calculation
Support and reflection coefficient
Support and reflectance Pixel … Patterns … Reflection Coefficient Resulting Value = → Error 1 = → Error 2 × Rpix, patch Find … = → Errorn-1 = → Errorn and Rpix, patch that minimize: Errork
Support and reflectance: examples cli ck left top back right
Three-step algorithm 2 1 Basis Image Recording 3 Relit image = Captured reflectance + Light-map Reflectance field calculation
Re-lighting For each pixel: Pixel value = ∑ support i Filteri(Light. Map) × Rpix, i
Results A B C D
Results A B C D
Results A B C D
Results A B C D
Comparison Stochastic ray tracing Relit from rendered basis images
Comparison Stochastic ray tracing Relit from rendered basis images
Comparison Stochastic ray tracing Relit from rendered basis images
Conclusion • Accurate relighting: – Diffuse materials – Specular materials • Combine strengths from: – The Light Stage – Environment matting
Future Work • Alternative emitting devices • Investigate other patterns & optimization algorithms
Acknowledgements • Frank Suykens and Vincent Masselus • Some environment maps from: http: //www. debevec. org/Probes
Thank you… Questions?
- Slides: 27