Stained glass still has the power today to put many under its shining spell. Our perception of it however is strongly influenced by exhibitions and illustrations that display these works of art as immobile images. Yet stained glass is anything but static: it transforms continuously with the changing light that passes through it, and with the changing background colourations. This transformation becomes especially vivid if, as was normal in earlier times, you gaze at a stained-glass window over a longer period of time, or look at it repeatedly. In the reddish light of dusk certain colours seem warmer than they do in harsh midday sun. This dynamic, which has been termed stained glass’s ‘fourth dimension’, are among the most essential characteristics of this transparent medium for images. With the revolving cycles of the day and the seasons, and even with the weather, stained glass is continually infused with new life, and its pictorial nature is ever characterized by its mediating role between internal space and the outdoors.
A research project undertaken by the Audiovisual Communications Laboratory (LCAV) of the École Polytechnique Fédérale de Lausanne in close collaboration with the Vitrocentre Romont has shown that these phenomena can be simulated computationally and visualized digitally. For the simulation, several thousand images of a work in stained glass were taken under very different light conditions. A ‘light transport matrix’ was extrapolated from this enormous quantity of image data that allows us to represent any work of our choice in any conceivable lighting condition.
The following animation shows what happens to stained glass when the colour of the light and its intensity change, and how diversely small air bubbles in the material and the unevenness of the glass surface scatter light rays as the light incidence varies.
Research collaboration between the Audiovisual Communications Laboratory (LCAV) of the École Polytechnique Fédérale de Lausanne and the Vitrocentre Romont. Research conducted by: Niranjan Thanikachalam (EPFL), Stefan Trümpler and Sophie Wolf (Vitrocentre Romont)
Publications and links
Niranjan THANIKACHALAM, Loïc BABOULAZ, Paolo PRANDONI, Stefan TRÜMPLER, Sophie WOLF, Martin VETTERLI, Vitrail: Acquisition, Modelling and Rendering of Stained Glass, in: IEEE Transactions on Image Processing, 2016, 4475–4448. (DOI: 10.1109/TIP.2016.2585041).
Stefan TRÜMPLER, Couleurs dynamiques … ou comment voir les vitraux autrement, in: NIKE Bulletin, 1/2019 (PDF).