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

2. The Free-form Light Stage2 Capture appearance of an object –With hand–held light source Relight real objects

3. The Free-form Light Stage3 Related work Image-based relighting –Combination of Basis Images [Nimeroff et al.1994] –Light Stage [Debevec et al. 2000]

4. The Free-form Light Stage4 Basis images Illuminant direction estimation Take pictures and move hand-held light source Incident light map Create weighted sum … · W 1 + · W 2 + + · W n Relit object

5. The Free-form Light Stage5 Taking the pictures

6. The Free-form Light Stage6 Relighting · W 1 + · W 2 + · W n-1 + · W n + … =

7. The Free-form Light Stage7 Take pictures and move hand-held light source Illuminant direction estimation Basis images

8. The Free-form Light Stage8 Illuminant direction estimation Diffuse white spheres

9. The Free-form Light Stage9 Illuminant direction estimation Lamberts Law I i = ρ I L ( N i · L) L N1N1 I1I1 L N2N2 I2I2 L N3N3 I3I3

10. The Free-form Light Stage10 Illuminant direction estimation

11. The Free-form Light Stage11 Illuminant direction estimation

12. The Free-form Light Stage12 A direction per basis image …

13. The Free-form Light Stage13 Accuracy of estimation Light source at infinity Area light source Virtual Maximum error: 1 degree Maximum error: 2 degrees RealN/A Maximum error: 7 degrees

14. The Free-form Light Stage14 Illuminant direction estimation Basis images Take pictures and move hand-held light source Incident light map Create weighted sum … · W 1 + · W 2 + + · W n

15. The Free-form Light Stage15 Weight computation Weight is based on incident light in neighborhood of light source direction Non-uniform sampling of light source directions use an angular Voronoi diagram

16. The Free-form Light Stage16 Plot directions on a hemisphere …

17. The Free-form Light Stage17 Plot directions on hemisphere 30 light directions

18. The Free-form Light Stage18 Create an angular Voronoi Diagram 30 light directions

19. The Free-form Light Stage19 Choose a parameterization

20. The Free-form Light Stage20 Filter the incident light map Filter each Voronoi cell Overlay incident light map with angular Voronoi diagram

21. The Free-form Light Stage21 400 light directions Using all illuminant directions 30 light directions

22. The Free-form Light Stage22Relighting … · W 1 + · W 2 + · W 3 + · W n

23. The Free-form Light Stage23 · W 1 + … · W 2 + · W 3 + · W n =Relighting

24. The Free-form Light Stage24 Illuminant direction estimation Basis images Take pictures and move hand-held light source Incident light map … + · W n · W 2 + · W 1 + Create weighted sum Relit object

25. The Free-form Light Stage25 Results 400 basis images

26. The Free-form Light Stage26 Results 400 basis images

27. The Free-form Light Stage27 Results 500 basis images

28. The Free-form Light Stage28 Results 500 basis images

29. The Free-form Light Stage29 Results 500 basis images

30. The Free-form Light Stage30 Results

31. The Free-form Light Stage31 Results

32. The Free-form Light Stage32 Augmented virtuality

33. The Free-form Light Stage33 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

34. The Free-form Light Stage34 Acknowledgements Frank Suykens and Pieter Peers Environment maps from: –http://www.debevec.org/Probeshttp://www.debevec.org/Probes –http://www.cs.kuleuven.ac.be/~graphicshttp://www.cs.kuleuven.ac.be/~graphics FWO Grant #G.0354.00

35. The Free-form Light Stage35