The Free-form Light Stage Vincent Masselus Philip Dutré Frederik Anrys Department of Computer Science
The Free-form Light Stage2 Capture appearance of an object –With hand–held light source Relight real objects
The Free-form Light Stage3 Related work Image-based relighting –Combination of Basis Images [Nimeroff et al.1994] –Light Stage [Debevec et al. 2000]
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 · W n Relit object
The Free-form Light Stage5 Taking the pictures
The Free-form Light Stage6 Relighting · W 1 + · W 2 + · W n-1 + · W n + … =
The Free-form Light Stage7 Take pictures and move hand-held light source Illuminant direction estimation Basis images
The Free-form Light Stage8 Illuminant direction estimation Diffuse white spheres
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
The Free-form Light Stage10 Illuminant direction estimation
The Free-form Light Stage11 Illuminant direction estimation
The Free-form Light Stage12 A direction per basis image …
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
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 · W n
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
The Free-form Light Stage16 Plot directions on a hemisphere …
The Free-form Light Stage17 Plot directions on hemisphere 30 light directions
The Free-form Light Stage18 Create an angular Voronoi Diagram 30 light directions
The Free-form Light Stage19 Choose a parameterization
The Free-form Light Stage20 Filter the incident light map Filter each Voronoi cell Overlay incident light map with angular Voronoi diagram
The Free-form Light Stage light directions Using all illuminant directions 30 light directions
The Free-form Light Stage22Relighting … · W 1 + · W 2 + · W 3 + · W n
The Free-form Light Stage23 · W 1 + … · W 2 + · W 3 + · W n =Relighting
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
The Free-form Light Stage25 Results 400 basis images
The Free-form Light Stage26 Results 400 basis images
The Free-form Light Stage27 Results 500 basis images
The Free-form Light Stage28 Results 500 basis images
The Free-form Light Stage29 Results 500 basis images
The Free-form Light Stage30 Results
The Free-form Light Stage31 Results
The Free-form Light Stage32 Augmented virtuality
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
The Free-form Light Stage34 Acknowledgements Frank Suykens and Pieter Peers Environment maps from: – – FWO Grant #G
The Free-form Light Stage35