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Daylight scattering by late antique window glass from Ephesos: Reconstructing the spatial distribution of daylight in lost architecture

Publication Type:

Conference Paper


International Conference on Cultural Heritage and New Technologies CHNT24, Propylaeum, Heidelberg, Germany, Vienna, Austria (2021)





BSDF, daylight simulation, Ephesus, material modelling, Roman window glass


Starting from the 1st century CE, the availability of window glass throughout the Roman empire fosters the utilization of daylight in architecture. Due to features introduced by manufacturing, it affects the spatial distribution of daylight in buildings, and thereby the visual perception of architecture. Finds of window glass in the context of a mixed-use, residential house, located in a late-antique – medieval urban quarter in Ephesus, ask for a sound understanding of these immaterial aspects of architecture on the perception and utilization of buildings. The reconstruction of the building’s illumination is challenging, since it has to replicate the effects of fenestration on admitted light, and therefore requires models of the light scattering by window glass. To prepare such a reconstruction attempt, two data-driven modelling techniques are evaluated. One is based on the direct characterization of light scattering by gonio-photometric measurements. The other technique employs ray-tracing on geometric surface models of the glass micro-structures, acquired by confocal microscopy, to derive effects on light scattering. The exemplary application of the techniques to an exemplary glass fragment from the site provides two models of the sample’s scattering properties, including effects of corrosion and other alteration mechanisms. Both modelling techniques achieve qualitative accordance and demonstrate the applicability of the resulting models in daylight simulation. Quantitative differences between the two models indicate the importance to also account for effects by the glass volume and inclusions. The research lays the foundations for the planned modelling of glass based on replicated samples and processed finds, and shall ultimately lead to a plausible reconstruction of the building’s illumination in late antiquity.