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The Free-form Light Stage

The Free-form Light Stage is a method for capturing and relighting real objects by taking pictures and manipulating a hand-held light source. It allows for easy and cheap data acquisition, is portable and scalable. Future work includes testing on large objects, alternative filters, and improving accuracy in illuminant direction estimation.

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The Free-form Light Stage

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  1. The Free-form Light Stage Vincent Masselus Philip Dutré Frederik Anrys Department of Computer Science

  2. The Free-form Light Stage • Capture appearance of an object • With hand–held light source • Relight real objects The Free-form Light Stage

  3. Related work • Image-based relighting • Combination of Basis Images [Nimeroff et al.1994] • Light Stage [Debevec et al. 2000] The Free-form Light Stage

  4. Illuminant direction estimation Take pictures and move hand-held light source Basis images · W1 + · W2 + · Wn + … Create weighted sum Relit object Incident light map The Free-form Light Stage

  5. Taking the pictures The Free-form Light Stage

  6. · W2 + · Wn · W1 + + · Wn-1 + … = Relighting The Free-form Light Stage

  7. Illuminant direction estimation Basis images Take pictures and move hand-held light source The Free-form Light Stage

  8. Illuminant direction estimation Diffuse white spheres The Free-form Light Stage

  9. Lamberts Law Ii = ρ IL ( Ni · L) L N3 I3 L N1 L I1 I2 N2 Illuminant direction estimation The Free-form Light Stage

  10. Illuminant direction estimation The Free-form Light Stage

  11. Illuminant direction estimation The Free-form Light Stage

  12. … A direction per basis image The Free-form Light Stage

  13. Accuracy of estimation The Free-form Light Stage

  14. Illuminant direction estimation Basis images · W1 + · W2 + · Wn + … Incident light map Create weighted sum Take pictures and move hand-held light source The Free-form Light Stage

  15. use an angular Voronoi diagram Weight computation • Weight is based on incident light in neighborhood of light source direction • Non-uniform sampling of light source directions The Free-form Light Stage

  16. … Plot directions on a hemisphere The Free-form Light Stage

  17. Plot directions on hemisphere 30 light directions The Free-form Light Stage

  18. Create an angular Voronoi Diagram 30 light directions The Free-form Light Stage

  19. Choose a parameterization The Free-form Light Stage

  20. Filter each Voronoi cell Filter the incident light map Overlay incident light map with angular Voronoi diagram The Free-form Light Stage

  21. 400 light directions Using all illuminant directions 30 light directions The Free-form Light Stage

  22. · W1 + · W2 + · W3 + · Wn Relighting … The Free-form Light Stage

  23. Relighting · W1 + · W2 + = · W3 + … · Wn The Free-form Light Stage

  24. · W1 + · W2 + · Wn + … Create weighted sum Relit object Illuminant direction estimation Take pictures and move hand-held light source Basis images Incident light map The Free-form Light Stage

  25. Results 400 basis images The Free-form Light Stage

  26. Results 400 basis images The Free-form Light Stage

  27. Results 500 basis images The Free-form Light Stage

  28. Results 500 basis images The Free-form Light Stage

  29. Results 500 basis images The Free-form Light Stage

  30. Results The Free-form Light Stage

  31. Results The Free-form Light Stage

  32. Augmented virtuality The Free-form Light Stage

  33. Conclusion • Relighting real objects • Easy and cheap data acquisition • Portable • Scalable • Future work • Test BIG objects • Alternative filters • Sampling density accuracy in illuminant direction estimation • For more info: see the EGWR ’02 paper The Free-form Light Stage

  34. Acknowledgements • Frank Suykens and Pieter Peers • Environment maps from: • http://www.debevec.org/Probes • http://www.cs.kuleuven.ac.be/~graphics • FWO Grant #G.0354.00 The Free-form Light Stage

  35. The Free-form Light Stage

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