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Accurate Image Based Relighting through Optimization

This work presents a novel approach to image-based relighting by optimizing the basis images and reflectance fields. It builds on previous methodologies, including seminal works like The Light Stage and Environment Matting, integrating techniques for accurate relighting of both diffuse and specular materials. The proposed three-step algorithm comprises basis image recording, reflectance field calculation, and the combination of captured reflectance with a light map to achieve photorealistic results. The research highlights practical setups using HDR photography and calibration methods, along with comparisons to stochastic ray tracing, paving the way for future developments in light manipulation technologies.

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Accurate Image Based Relighting through Optimization

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  1. Accurate Image Based Relighting through Optimization Pieter Peers Philip Dutré Department of Computer Science K.U.Leuven, Belgium

  2. What is Image Based Relighting? Basis Images Relit Image Processing & Relighting

  3. Previous Work • The Light Stage (Debevec et al. ’00) Images: ACM SIGGRAPH ‘00

  4. Previous Work • Environment Matting (Zonker et al. ’99, Chuang et al. ’00) Images: ACM SIGGRAPH ’99

  5. Previous work Sparse sampling of light source directions Sufficient angular sampling Large span of incominglight directions Bundled incominglight directions • Matusik et al. EGWR’02

  6. Three-step algorithm 2 1 Basis Image Recording Reflectance field calculation 3 Relit image = Captured reflectance + Light-map

  7. Basis Image Recording

  8. Basis Image Recording

  9. ... Basis Image Recording HDR photographs

  10. Practical Setup • HDR photographs • Monitor calibration • 4x4 grid, 9 patterns per lightpatch • ±600 basis images

  11. Three-step algorithm 2 1 Basis Image Recording Reflectance field calculation 3 Relit image = Captured reflectance + Light-map

  12. Support and reflection coefficient

  13. Reflection Coefficient Resulting Value →Error1 = = →Error2 × Rpix,patch … = →Errorn-1 = →Errorn Find and Rpix,patch that minimize: Errork Support and reflectance Patterns Pixel … …

  14. top back left right Support and reflectance: examples click

  15. Three-step algorithm 2 1 Basis Image Recording Reflectance field calculation 3 Relit image = Captured reflectance + Light-map

  16. Re-lighting For each pixel: Pixel value = ∑ Filteri(LightMap) × Rpix,isupport i

  17. Results B A D C

  18. Results B A D C

  19. Results B A D C

  20. Results B A D C

  21. Comparison Relit from rendered basis images Stochastic ray tracing

  22. Comparison Relit from rendered basis images Stochastic ray tracing

  23. Comparison Relit from rendered basis images Stochastic ray tracing

  24. Conclusion • Accurate relighting: • Diffuse materials • Specular materials • Combine strengths from: • The Light Stage • Environment matting

  25. Future Work • Alternative emitting devices • Investigate other patterns & optimization algorithms

  26. Acknowledgements • Frank Suykens and Vincent Masselus • Some environment maps from: http://www.debevec.org/Probes

  27. Thank you… Questions?

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