Enhanced RTI for gloss reproduction

The Digital Humanities Lab (DHLab) is a technological oriented research group within the faculty of Humanities of the University of Basel. The research profile of the DHLab integrates computer science, digital imaging, computational photography, the accessibility of digital objects and solutions for digital preservation with the aim to support scholars in the emerging field of humanities research. The project Digital Materiality, a collaboration with the Seminar of Art History, examines how new imaging and visualization methods can be applied to describe the reflection of light on surfaces of artworks. Of main interest are mosaics and early prints; both types of artworks have a strong interaction with light that can not captured adequately by standard photographic approaches. Conventional photographic processes are not able to capture the dynamic component of the light-surface interdependence that is specific for this kind of art. The technical part of the project focuses on improving the methodology that is in general described as Reflectance Transformation Imaging (RTI) techniques. RTI is an approach based on a mathematical model, that is fitted in image data derived from photographs. By modifying the mathematical model that is used to represent the light-surface interaction, the digital reproduction can be improved so that relevant attributes of artworks can be transported into the digital domain in such a way that the requirements and needs of humanities researchers to a digital representation can be fulfilled. The improvements take into account more sophisticated but still robust and simple reflection models for the realistic visualization of localized diffuse and specular surfaces within the same digital reproduction. For humanities research the most important aspect is the compatibility to web-based Virtual Research Environments (VRE). The presented approach can be integrated in such environments because the client-side visualization is implemented in WebGL. For flexibility, performance and data permanence aspects the server side will be an enhanced image server layer following the International Image Interoperability Framework (IIIF) image based environment.