Tuesday, June 20, 2017

Experimenting with 3D integration in OCRE

The Wild West of 3D Capture in Cultural Heritage

The lowered technical barriers and costs of 3D capture (especially photogrammetry) within the museum and archaeology domains has seen an explosion of 3D data within the cultural heritage sector. The Smithsonian X 3D and British Museum (led by Nomisma scientific committee member, Dan Pett) endeavors are among the best recognized efforts in this area, but 3D cultural heritage models (from artifact scans to excavation trenches and entire sites) are being published to the web by many organizations through a wide variety of information systems. Many organizations have turned to Sketchfab as the primary mode of publication, but others are using home-grown systems. In truth, 3D publication is the wild west. There aren't even readily agreed-upon open standards for the models themselves, let alone metadata standards, publication frameworks or APIs for accessing models/metadata (in contrast to 2D images through IIIF standardization).

As such, integration of 3D data back into the scholarly research ecosystem has fallen very far behind 3D production capacity. We have seen that Sketchfab models can be embedded into web-based news articles or blogs (such as the Telegraph article above or Sarah Bond's recent post on Forbes), which have been an excellent medium for making these resources available to a general audience. However, we cannot overlook the fact that these are also valuable resources to a scholarly audience, and this audience isn't going to poke around various universities' institutional repositories or Sketchfab profiles for relevant 3D data. Numismatists studying Roman imperial coinage use Online Coins of the Roman Empire, and if there are 3D models of Roman coins, they should expect to access that material through OCRE and not Sketchfab directly. The same goes for Greek pottery experts and Kerameikos.org. Scholars more broadly interested in the ancient world may access 3D objects through Pelagios and more general audiences (both academic and public) may interact with these objects through Europeana or DPLA.

I have high hopes that the 3D GLAM community (including commercial entities such as Sketchfab) will move toward open standards for the dissemination of these data. Taking Greek pottery as an example, 3D models are much preferred over 2D photography for viewing inscriptions and iconography, and if 3D models can be annotated following the same standards we see in IIIF (Open Annotation RDF), scholars will be able to view all objects depicting Dionysus, regardless of the 2D/3D medium of capture.

Sketchfab models in OCRE, a Proof of Concept

The coin cabinet of Heinrich-Heine-Universität Düsseldorf, a Nomisma partner through the NUMiD network of German university coin cabinets, recently uploaded three models to Sketchfab: a Roman provincial coin showing the damnatio memoriae of Geta, an imperial coin of Severus Alexander (RIC IV 455), and an imperial coin of Constantine (RIC VII Constantinople 126). The latter two coins have already been integrated into OCRE, and so I set forth on the task of incorporating triples for the 3D models into the RDF for these two coins.

Fortunately, two librarians at the University of South Florida, Xiying Mi and Bonita Pollock, have put forth a useful proposal at ALA (see Linked Metadata for 3D-Models: From Dublin Core to Europeana Data Model) to capture some basic 3D model metadata and associate this information with the cultural heritage object.

Since we have already implemented the IIIF extension for the Europeana Data Model in Nomisma, it was fairly straightfoward to link to a 3D model in much the same manner by using the edm:isShownBy property to link to the Sketchfab URI, which is cast as an edm:WebResource class. This edm:WebResource carries some additional metadata about the model itself, including the capture process (photogrammetry as a dcterms:format linking to a Getty AAT URI, etc.).

A 3D model of a coin of Severus Alexander, shown in OCRE
These data model adaptations were followed by some updates to Numishare's underlying SPARQL query and UI scripts to render the 3D model, when available. There is a conditional within the Javascript to use an iframe to embed the Sketchfab model when the edm:WebResource is a Sketchfab URI. So far, there's only one condition for rendering. Ultimately, the scripts will read the mime-type from the RDF metadata and use an open source JS 3D library accordingly (such as Universal Viewer).

This of course is predicated on the cultural heritage community coming to an agreement on open standards for 3D models and APIs for accessing these models and associated metadata. In this endeavor, I see myself as a consumer of 3D--not for my own research purposes, but as a technical developer building middleware for scholars to access the models to achieve their needs. In my role as a consumer, I hope to be able to steer the content producers and architects of 3D information systems onto a path that results in the greatest potential for reuse and synthesis.

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