2. Mesostructure from Specularity Using Coded Illumination
Yannick Francken, Tom Mertens, Jo Gielis, Philippe Bekaert
Expertise Centre for Digital Media
Hasselt University (Belgium)
{yannick.francken, tom.mertens,

3. Goal
Acquire mesostructure’s normal map
Mesostructure
Normal map

4. Previous Work
Shape from shading [Horn75, Zhang99]

5. Previous Work Shape from shading [Horn75, Zhang99]
Photometric stereo [Woodham89, Ikeuchi92] …

6. Previous Work Shape from shading [Horn75, Zhang99]
Photometric stereo [Woodham89, Ikeuchi92]
Structured light [Boyer87, Scharstein03]

7. Previous Work Shape from shading [Horn75, Zhang99]
Photometric stereo [Woodham80, Ikeuchi92]
Structured light [Boyer87, Scharstein03]
Mesostructure scanning
Mesostructure from Specularity [Chen06] …

8. Previous Work Shape from shading [Horn75, Zhang99]
Photometric stereo [Woodham80, Ikeuchi92]
Structured light [Boyer87, Scharstein03]
Mesostructure scanning
Mesostructure from Specularity [Chen06]
Rapid Acquisition of Specular and Diffuse Normal Maps from Polarized Spherical Gradient Illumination [Ma07]

9. Previous Work Mesostructure from specularity [Chen06] Setup
Image captures

10. Previous Work Mesostructure from specularity [Chen06]
Detecting specularities
Law of reflection
V = 2(NTL)N - L L V N

11. Observation A specularity is caused by one light source 1011 1100 100
1001 10 1
1101
1010
1001
1110
1000
1111
O(log N) instead of O(N) image captures!

12. Setup Screen-camera setup Binary coded light patterns
Screen as cheap controllable light source [Zongker96, Tarini05, Clark05, Funk06]
Calibration [Hartley04, Tarini05, Francken06, Funk06]
Binary coded light patterns
Gray code
M x N light sources  log2M + log2N + 1 patterns

13. Results

14. Limits
Only specular mesostructures
Sharp specular highlights  

15. Limits Only specular mesostructures Sharp specular highlights
Limited cone of normals
Planar display

16. Limits Only specular mesostructures Sharp specular highlights
Limited cone of normals
Planar display
Self shadowing

17. Conclusion Efficient Inexpensive setup O(log N) instead of O(N)
Longer exposure times  less noise
Inexpensive setup
Only controllable binary light source

18. Future Work Smoothness constraints
Using specular and diffuse components
Surface adaptive patterns
Colored patterns instead of binary
Hemispherical light source

19. Questions? Summary Efficient Inexpensive setup
O(log N) instead of O(N)
Longer exposure times  less noise
Inexpensive setup
Only controllable binary light source