Modeling And Visualization Of Aboriginal Rock Art in

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

Where is Newcastle?

Outline 1. 2. 3. 4. 5. 6. Motivation and requirements. Proposed approach. Movie Some Details Results of Modeling the Baiame cave. Conclusions.

Why 3 D 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

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

The Baiame Cave Location

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

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

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.

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

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

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

Rock Art in Baiame Cave - The Movie

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

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)

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

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

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

The Baiame Cave , Data Collection Riegl® Z 210 i Leica® Total Station + Nikon® Cool Pix digital camera

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

Image Locations Top view Available image locations Poor geometric configurations

Commercial Software Tools • Poly. Works® 8 • Shape. Capture® 5 • 3 ds max® 5 • Adobe Premier® 6 3 D Modeling Bundle Adjustment Rendering Movie Editing

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

Image-Based Model

Scanner Model

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 3 D experience.

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.