Polynomial Texture Mapping of Medieval Islamic Pottery
Lustre ware is a type of pottery decorated with a paint that contains silver and copper ions which react with the surface glaze during a second firing to create a thin surface layer that is shiny and metallic in appearance. It was produced at a number of centres in the Medieval Islamic World, from 9th century Basra (modern day Iraq) to 12th to 14th century Kashan (modern day Iran). Mina'i ware is a type of pottery which was made alongside lustre at the Kashan kilns during the late 12th to early 13th centuries. Often the surface of mina'i was embellished with gold leaf, creating a similar shiny, metallic effect to lustre. Unlike lustre, however, this gold leaf was combined with a range of colourful paints to create a polychrome effect.
The Fitzwilliam Museum holds 97 pieces of medieval lustre ware and 22 pieces of mina'i ware. These pottery types form a significant part of the museum's Islamic pottery collection that is currently being investigated and recorded by Dr Rebecca Bridgman. As part of this project, and in collaboration with Dr Graeme Earl (University of Southampton), a selected number of the Fitzwilliam's Islamic pottery vessels were recorded using a new technique called polynomial texture mapping (or PTM). PTM was developed at Hewlett Packard by Tom Malzbender and Dan Gelb; it uses a combination of varying lighting conditions and digital photography to record a surface map of objects. The resulting map enables objects to be re-lit and viewed in a way that has hitherto only been accessible to people handling and closely examining the objects themselves. Dr Graeme Earl is currently co-ordinating the development of the PTM technique for use on a range of object types with funding through an Arts and Humanities Research Council grant.
The outcome of this collaboration is a series of PTM files, examples of which can be viewed here.