1. Modeling And Visualization Of Aboriginal Rock Art in The Baiame Cave
Sabry El-Hakim,
Michel Picard
Visual Information Technology,
National Research Council Canada
John Fryer
School of Engineering,
University of Newcastle, Australia

2. Where is Newcastle?

3. Outline Motivation and requirements. Proposed approach. Movie
Some Details
Results of Modeling the Baiame cave.
Conclusions.

4. Why 3D Modeling / Digital Archiving for Cultural Heritage ?
Documentation in case of loss or damage
Educational resource
Visualization from new viewpoints
Interaction without risk of damage
Virtual tourism and virtual museums

5. Australia’s Aboriginal Rock Art
World’s oldest art
Unprotected - Fast deteriorating
Inaccessible – Not enjoyed by most
Why Baiame?

6. The Baiame Cave Location

7. Requirements High geometric accuracy Complete detail Photo-realism
Low cost
Portability

8. Automated Image-Based
Current Techniques
Direct Tracing
Photography
Field Notes
Traditional Rock Art
Surveying
Photogrammetry
Standard Mapping
Laser Scanning
Automated Image-Based
Emerging
2-D Only
3-D on selected
points only
Potential full 3-D with photo-realism

9. Comments and Objective
The efficient integration of image-based modeling and laser scanning, each where best suited, for recording Aboriginal rock art is the objective of this research.

10. Technology Selection Image-Based Methods Low cost sensor
Require features **
Difficult on fine details
Object size independent
Manageable data size
Portable
Laser Scanning
High cost sensor **
No features required
Give fine details
Object size a factor
Huge data size
Bulky
** The problems for this application

11. Error Sources : Image-based, Laser-scan and Geometric Configurations (see example)
Mainly B/D (base/depth) ratio
B is the component parallel to the object.
B/D Ratio
Images 1-3 Good
Images 3-2 Poor

12. - Compression & editing
The Proposed Solution
Laser Scanning
3D Geometry Capture
Digital Imaging
Texture Capture
Surveying
Reference Frame
Scans Registration
Noise filtering
Bundle Adjustment
Texture Registration
With 3D Geometry
Post Processing
- Compression & editing
- Texture matching
Visualization

13. Rock Art in Baiame Cave - The Movie

14. Problems With Rock Art Modeling (Image-Based Techniques)
Difficult to find ideal locations to take the images (rocks, trees, water,..etc)
Insufficient features in multiple images
No geometric constraints to increase automation

15. Problems With Art Rock (Laser Scanning)
Texture / color acquisition: most scanners do not provide good solution
Registration of scans and scans with texture: require features
Noise level, particularly for lower cost scanners: Noise level can be the same size as many geometric details (the rocks)

16. Best Solution Geometry from laser scanner to get all geometric details
Texture from a separate high resolution digital camera

17. But we must have accurate registration, even without common features or targets, otherwise:
Features spanning two images may not align
Geometry and color do not match

18. Texture Mapping
Correct registration but texture color / lighting must be corrected
Uncontrolled illumination

19. The Baiame Cave , Data Collection
Riegl® Z210i
Leica® Total Station
+ Nikon® Cool Pix digital camera

20. Surveying Useful Points
Not useful: no detectable geometry in the 3D model

21. Image Locations Top view Available image locations
Poor geometric configurations

22. Commercial Software Tools
PolyWorks® D Modeling
ShapeCapture® Bundle Adjustment
3ds max® Rendering
Adobe Premier® Movie Editing

23. Accuracy Numbers Laser scanning: +/- 30 mm Surveying: +/- 2-3 mm
Bundle Adjustment: X: +/- 13 mm,
Y: +/- 9 mm,
Z: +/- 11 mm

24. Image-Based Model

25. Scanner Model

26. Comments on the Results
The results of the laser scanner were noisy and did not capture all fine geometric details. This caused problems with registration, particularly since the data had to be smoothed to reduce the noise.
The image-based model was not detailed enough and resulted in unrealistic 3D experience.

27. Conclusions
Our approach uses some surveying, laser scanning, digital images with a bundle adjustment to register the texture with geometry without targeted points.
The resulting model is realistic and was created in a short time at low cost.
It is still not clear what accuracy is really needed. Although rocks do not need to be modeled with high accuracy, poor accuracy will result in visible registration errors.