Image-based models using crowdsourcing strategies

This paper aims to highlight the effectiveness of the collaboration between the modelling techniques that exploit the stereoscopic images of objects and the ability of the present-day technologies to generate images, both found in the web and gathered by other crowdsourcing techniques. Since nowadays the generation of models from images is a major low-cost resource, the whole strategy is aimed at obtaining benefits in the context of the documentation of Cultural Heritage (CH). Assuming that the documentation of CH is the basis of the protection and the conservation policies, the chances of finding images and using them to create 3D models is particularly effective when the assets in question are at risk in danger zones (wars or areas subject to natural disasters) or in areas that, for various reasons, are difficult to access. To demonstrate the advantage of using low-cost methods for the generation of 3D models of documentation with strategies that fall within the sphere of crowdsourcing, the case of the Vank cathedral modelling is presented. The Vank Cathedral in Isfahan in Iran is a building of the Safavid epoch (cent. XVII–XVIII) completely frescoed in the internal surfaces, where the architecture and especially the architectural decoration reach their peak. The experimental section of the paper also explores some aspects of usability of the digital output from the image-based modelling methods. The availability of orthophotos allows and facilitates the iconographic reading of the frescoes, adding to the radiometric data, there is the metric potentiality of reading the proportions and the compositions of the organisation of the frescoes. Furthermore, simplified and suitably schematised models can be even printed and can be used in a didactic environment, such as the knowledge dissemination intended by the museums and other cultural institutions.