1. SmartBoxes for Interactive Urban Reconstruction
Liangliang Nan1, Andrei Sharf1, Hao Zhang2, Daniel Cohen-Or3, Baoquan Chen1
1 Shenzhen Institutes of Advanced Technology (SIAT), China
2 Simon Fraser University, Canada
3University of Tel Aviv, Israel

2. 3D Cities
Virtual Philadelphia
Virtual Berlin

3. Acquisition of Urban Environments
Remote Sensing Systems
Airborne LIDAR
Cameras/videos
Auto-mounted LIDAR
3D Digital City 3 3

4. 3D LiDAR scanner Street-level 60km/h 180 pitch [100-300m] range
100K points/second
5cm XY accuracy

5. Outdoor Urban Scanning

7. Imperfect Scans - Occlusions
Point cloud contains holes due to various occlusions (“shadows”)

8. Imperfect Scans – Angle & Range
Oblique scanning angle
Laser energy attenuation on range

9. Urban Building Characteristics
Dominant planes
Axis-aligned basic primitives
Repetitions, intra symmetry and regularity

10. SmartBoxes
Box-up and Smart!

11. SmartBoxes Box prior shape fitting Smart context awareness Data
Both

12. Live Demo

14. Related Work
Procedural modeling of buildings and facades [Wonka2003;Muller2007]
Automatic 3D reconstruction from 2D images [Zisserman2002;Xiao2009;Furukawa2009]
Interactive modeling of architectural structures [Debevec1996;Schindler2003; Xiao2008;Sinha2008;Jiang2009]
Primitive fitting to data [Gal2007; Schnabel 2009]

15. Preprocessing
Automatic detection of planes and edges assuming dominant orthogonal axes
RANSAC planes
Line sweep edges

16. Snapping a Box 2D rubber band ROI Collect planes, edges, corners
Find the best fitting box using data fitting force D(B,P)

17. Data fitting D(B,P) snap
Data fitting force
Facet
Edge
Data quality
(Confidence + Density)
Distance

18. Grouping Simple SmartBox Compound SmartBox
Align to remove gaps and intersections
cluster and align close to co-linear edges

19. Drag-and-drop context C(Bi-1, Bi)
The context of Bi
Interval
Alignment
Scale Bi
Bi-3
Bi-2
Bi-1
•••
Context

20. Drag-and-drop context C(Bi-1, Bi)
The context of Bi
Interval term Bi
•••
Bi-3
Bi-2
Bi-1

21. Drag-and-drop context C(Bi-1, Bi)
The context of Bi
Alignment term Bi
•••
Bi-3
Bi-2
Bi-1

22. Drag-and-drop context C(Bi-1, Bi)
The context of Bi
Scale term Bi Bi
•••
Bi-3
Bi-2
Bi-1

23. Discrete objective minimization
Find linear transformation T(excluding rotation) to minimize:
Data fitting force
Contextual force

24. Discrete objective minimization
Find linear transformation T(excluding rotation) to minimize:
Data fitting force
Contextual force
•••
Bi-3
Bi-2
Bi-1

25. Balance between two forces

26. Emerging city of Shenzhen, China

27. Results: textured buildings

28. The Crooked House (Sopot, Poland)
Manchester Civil Justice Centre (Manchester, UK)
Habitat 67 (Montreal, Canada)

29. (Thank You)!