Multi-Resolution Digital 3D Imaging & Modelling applied to the Documentation of rock art sites: Grotta dei Cervi in Italy J.-A. Beraldin 1, V. Valzano 2, A. Bandiera 2 1 IIT, National Research Council Canada, Ottawa, Ont, Canada, K1A OR6 2 SIBA, University of Salento, LE, Italy, 73100
High-Res 3D imaging for rock art sites Textured 3D, Why? Record, What? It: Grotta dei Cervi: Eng: Stag Grotto Fr: Grotte des Cerfs 3D documentation of rock art sites Understanding 3D imaging Some results and Discussion Conclusion Outline
Textured 3D models: 3D media model
High-resolution 3D imaging for rock art sites Site closure or limited access Researchers: examine, measure, compare Control: signs of deterioration Tool marks: verify hypothesis related to art history Virtual restoration: graffiti removal Display is interesting for both public & researchers Immersive 3D VR theater View model in a more natural hypothetical illumination context
What to record? Rock art: walls, crypts, grottos Formed naturally or created by people Rock formations and hence irregular shapes Paintings (pictographs) Carvings incisions (petroglyphs) Concretions stalactites/stalagmites (speleothems) 3D imaging or sensing: Explicit geometric measurement Dense sampling There is a match! Lots of details to be measured
Formed naturally or human activity
Some projects: rock art Caves, Crypts, Petroglyphs, Pictographs: Altamira Lascaux Lascaux II Cosquer: EDF 1994 Tomb of St-James (Arcosolia room): NRC 1996 Carpiniana: SIBA+NRC 2001 Baiame Australia And many more
Neolithic cave Grotta dei Cervi (Stag), Italy Porto Badisco, Southern Italy (5 th millennium BCE) 40 04 47 N, 18 29 02 E Depth: 26 m, RH: 98%-99.99%, 14 C - 18 C Many pictographs (Guano, Ochre) and speleothems and some petroglyphs 3 corridors about 300 m each, < 6 m diameter Very little information available; discovered in 1970 Pictographs in central corridor have deteriorated since Measures to slow down the decay: Closure of cave to limit human visits Restrict air flow with doors
Grotta dei Cervi: 1970 s survey 26 m
Working in the field Environmental: Temperature Humidity Particles, etc. Operational: Power Safety Scheduling Stability Accessibility/coverage
Combination of Multiple Techniques Reference frame, major elements and outlines Existing drawings and floor plans Surveying Semi-automated modeling from aerial and ground images Some data available Automated modeling from image sequences Fine Geometric details Laser scanning Raw data only 4 chambers
Active sensing Technology Triangulation (angle of reflected light): Controlled illumination for excellent contrast In practice, up to 10 m (1000 100 000 pts/s) Errors in µm/mm @ $$/$ Time of flight (delay/phase/beat frequency): Laser beam / Medium to Long range entire sites > 1m (100 500 000 pts/s) Errors in µm/mm/cm @ $$$/$$/$ $=10K, $$=100K
CAD Acquiring 3D information : White Light pattern projection/ Laser scanner : Stereoscopic Correspondence TOF Laser scanner
The operator is part of the chain! 36 000-polygon model 20 000-polygon model Same 3D data & modelling software; different operator
The Coverage and resolution problems Solutions: Multiple-view acquisition/registration/integration Well established algorithms Increased time Field-reconfigurable range camera On-site calibration Resolution, uncertainty, accuracy verification Single scanner head??? Yes : NRC Canada Big-Scan system
NRC Canada Big-Scan system
Big-Scan: Large field system Triangulation system with variable resolution: - lateral: z - depth: z 2 Error z 3D Scanner x
Standoff: 0.5 m - 5 m 0.2 Field of view: 0.16 40 40 degrees 0.12 Depth uncertainty : 0.08 mm @ 0.8 meter 0.08 Size of each image : 0.04 up to 4K 4K pixels 0 Lateral sampling: 0.2 mm to 2 mm Acquisition rate : 10 000 3D+I points per second Depth uncertainty (mm) Scanner Spec. Close range performance 0.5 0.7 0.9 1.1 Distance (m)
Some results Lateral resolution 0.2 mm Depth uncertainty 0.08 mm
Grotta dei Cervi, Italy
VR theater
1970 analog photo to 2008 3D model!
3D Model building CONCLUSIONS Most of the time spent goes into finding next best view Problems: Vibrations, Material effects Site safety: people and environment R&D issues: Speed: texture and 3D modelling Took NRC technologies development for the Mona Lisa project and adapted them to the Grotta dei Cervi! 3D model completion: The first scans: end of 2009 Spring 2009: return with medium volume scanner to connect the rooms together
The team
3D, SCIENCE ET PATRIMOINE CULTUREL 3D, SCIENCE AND CULTURAL HERITAGE Metz, France 19-23 Novembre 2008 Computer Aided Modelling and Exploration of the Grotta dei Cervi and Virtual Reconstruction of the Broken Frescoes of the Assisi Basilica. SAMEDI 22 NOVEMBRE 15H15-16H15 Visioconférence: Pr. Éric PAQUET Conférence: J-Angelo BERALDIN et Adriana BANDIERA