3D Virtual Modelling of a Gothic Stained-Glass Panel.

The paper illustrates laser scanning methodology applied to the study of a gothic stained-glass window: the work can help understanding how glass objects are measured by laser scanner, conforming to more parameters. A glass window from King’s Chapel, Cambridge (UK) was modelled: a vertical ensemble, divided into more parts, made of glass, coloured during its realisation or coloured before being placed on the wall. Thus, a different sensitivity to laser beam is expected from glass. The acquisition was performed using Konica Minolta Vivid 910, with a 5 x 8 scan matrix. Registration via ICP algorithm was carried in 8 horizontal stripes. Scans seem to be quite homogeneous, except some lacunas, probably depending on a “brownout-effect” induced by the presence of stain structure, partly obscuring glass surface. Otherwise they could be depending on local condition of glass, causing loose of signal from the surface. Some details show a particular noise in the acquisition, probably caused by an outdoor metal scaffolding, especially in more transparent areas. A comparison with the acquisition of an object protected by a glass showcase is illustrated too, to study the response of glass material. It was argued that glass painted with non covering colours is more sensitive to such object while covering colours (or coloured glass) “stop” laser beam and give no noise. Besides with painted sheets, a 3D laser scanning model can give a sub-millimetrical mapping with the thickness of colour layers: thus, noise induced by the metal scaffolding can be evaluated too.