3D ICONS Workshop at ISPRS 2014

Presentation in progress at the 3D ICONS workshop

On Tuesday June 24th, in the framework of the ISPRS Technical Commission V Symposium 2014 held at Riva del Garda (TN, Italy), the 3D ICONS workshop have been presented in the Room Belvedere of the Riva del Garda Conference Centre, and chaired by Gabriele Guidi.

The program included the following presentations:

  • 3D digitization of bronze and gold artefacts from Romanian National History Museum's collections  - C. Nicolae, MNIR, Romania
  • The 'Rubble of the North' - a solution for modelling the irregular architecture of Ireland's historic monuments - R. Shaw and P. Griffin, Discovery Programme, Ireland
  • Digitisation, processing and visualisation of monuments within the 3D-ICONS framework: The case of Athena RC - A. Koutsoudis, Athena Centre, Greece
  • Analysis of the 3D reconstruction methodologies used within the framework of the 3D-ICONS project - L. De Luca, CNRS, France
  • The last mile of 3DIcons: making available 3D contents and their metadata through Europeana - S. Gonizzi, Politecnico di Milano, Italy

The presentations have shown a manifold activity of the different partners, introducing several interesting results.

Image of silver helmet with gold impressions

Silver helmet with gold impressions

Corina Nicolae , From MNIR  (Romania), showed the complex 3D capturing work on three museum objects: an helmet made of silver with gold impressions and an helmet made of gold, both from the second half of the 4th century BC, and a bronze statuette of Jupiter Dolichenus from the second half of the 2nd century AD.

Since the unit made use of automatic photogrammetry techniques based on SFM, the major difficulty here was to gather a suitable 3D model from such shiny objects.

MNIR solved the problem taking great care in the image capturing phase. They used digital Single Lens Reflex (SLR) cameras (Canon EOS 5D Mark II and Fuji XS-1), and a so-called “soft box”, an opaque white box, large enough for accommodating the objects, illuminated by artificial lights. The effect of the soft box is to uniformly diffuse the light all around the object, possibly minimizing highlights that typically prevent the capturing of 3D information, when present.

As a result, objects very difficult to capture (specially the one shown on figure 1b), have been successfully modeled and textured for the 3D-ICONS project.

Rob Shaw  and Patrick Griffin , from the Discovery Programme  (Ireland), after an overview on the various kind of material that unit have been digitizing, represented by landscapes, buildings, monuments and artefacts, has shown in detail the digitization of St Kevin’s Church, in Glendalough (Ireland), a stone-roofed building dated back to the sixth century AD.

In addition to the typical issues involved in the 3D laser scanning of a cultural heritage asset like this, they shown the creation of textures - suitable for easy re-projection on the model - through the creation of a spherical panorama taken with a digital SLR camera Canon EOS 5D Mark II, a motor driven panoramic head Gigapan Epic Pro, and the stitching software PTGui. Then they introduced an interesting post-processing based on computer graphics techniques for making usable on the web the large models originated by laser scanning.

Summary of the DISC workflow for obtaining a 17 MB textured model out of a 7.5 GB original point cloud generated by scanning the church of St Kevin’s Church, in Glendalough (Ireland).

Summary of the DISC workflow for obtaining a 17 MB textured model out of a 7.5 GB original point cloud generated by scan

The original 3D cloud was in fact 7.5 GB and the whole 3D model after meshing and texturing could have been of the same order of magnitude. They instead applied a re-topology function to the initial high resolution mesh, reducing the model size to a fraction of the original (10.4 MB) and reapplying the visual details on the model through normal mapping, reaching a final size of 17MB. A model of such size, differently from the original one, becomes usable also in a web environment, making it suitable for publication on EUROPEANA. Figure 2 summarize the process that was applied also to the Market Cross, another important artefact in the same archaeological area of Glendalough.

A final point reported by the two speakers was a contact they had with the Autodesk company for the possible supply to 3DICONS of the same 3D web viewer Autodesk designed for the Smithsonian museum (http://3d.si.edu), capable to manage 3D models structured in this way.

 Anestis Koutsoudis , from the Athena Research and Innovation Centre/CETI (Greece), shown the pipeline used by the unit for the digitization of six ancient buildings:

  • Kioutouklou Baba Bekctashic Teke
  • Church of the Holy Apostles
  • Church of the Acheiropoietos
  • Church of St. George (Rotunda)
  • Monastery of Panagia Kalamou
  • Monastery of Panagia Kosmosotira

In addition to traditional methods with total stations, direct measurements and terrestrial laser scanning, CETI used primarily automatic photogrammetry techniques based on SFM, implemented in the software Photoscan by AGISOFT (Russia).

The main issues were related to the large size of the assets acquired, that involved areas of the buildings considered, hard to reach with and handheld camera or a tripod.

CETI used therefore both terrestrial and aerial photo sessions. In the latter case an hexacopter drone equipped with GPS was used.

As a result, a large number of images was needed to represent them at high resolution, ranging from 1000 of the Kioutouklou Baba Bekctashic Teke, to the 9200 of the Church of St. George (Rotunda), involving relatively high processing time for the image orientation (~190 hours with a PC equipped with an Intel i7 6-core CPU at 3.4Ghz and an ATI Radeon R9 200 graphic controller).

Dense point clouds originated by the image matching on the 6 monuments 3D digitized by CETI.

Dense point clouds originated by the image matching on the 6 monuments 3D digitized by CETI.

Finally a nice video of the final results on the Monastery of Panagia Kosmosotira, also published on youtube, was shown (https://www.youtube.com/watch?v=WogX7QCmfBw ).

Livio de Luca , from CNRS  (France) prepared his presentation about “Analysis of the 3D reconstruction methodologies used within the framework of the 3D-ICONS project” and sent it to the conference, but was unfortunately able to attend it for health reasons.

Finally Sara Gonizzi , from Politecnico di Milano  (Italy), shown the process developed in Milan for generating the large number of metadata record required for the many 3D models they are producing, needed for the publication to EUROPEANA.

Many of the 527 3D digitizations that POLIMI have produced are related to museum artifacts whose descriptive records were theoretically available through a specific regional database (SIRBEC). Actually, once accessed to the real data, a much more fragmented situation appeared, with some data available on the SIRBEC data base, some on a different internal data bases. In addition some technical metadata (paradata) needed to be collected in part from the project files of the automatic photogrammetry platform (AGISOFT Photoscan), and other complementary information from plane ASCII files.

A custom software have then been produced by POLIMI for merging in coherent way all the mentioned data types in a xml format file compliant with the CARARE data model, used by the transformation tool of the 3DICONS project, and therefore with the Europeana Data Model (EDM), whose data structure is the minimal mandatory for passing the acceptance test of the EUROPEANA portal.

Data processing for the generation of the xml files containing both metadata and paradata, ready to be ingested in EUROPEANA.

Data processing for the generation of the xml files containing both metadata and paradata, ready to be ingested in EUROPEANA.

All the presentations raised interest from the public and a considerable level of discussion which made the event useful both for the project representatives and the audience.