girih tiles
help or crucial?
Wat was the role girih tiles played? Hankin mentioned them first in the Western world but places them as an aid in the use of so called 'strapwork' that uses rule and compass for constructions. Lu and Steinhardt argument that the use of the tiles played a crucial role in the construction itself. The opinion of specialists differs.
Hogendijk
Hogendijk is critical and argues only one text remains that explains how a certain drawing is to be constructed. As in the drawings of the Topkapi scroll the lines of the girih tiles are visible, but this text explains how to create it. He continues: "In the mosaic in the Friday Mosque of Isfahan the girih tiles aren’t visible and it is clear that they didn’t play a role in the production process. This is to say that it weren’t the girih tiles that were fabricated (cut out or baked) and matched to create the pattern. This means that the tiles belong to the design phase."
Cromwell and Bonner
Cromwell quotes Bonner: "Bonner argues the PIC (the Polygons in Contact of Hankin) is the only system with historical proof that it was used by designers throughout the Islam world."
Lu and Steinhardt
"The use of girih tiles has practical advantages and allows easier,
faster and more correct realisations by workers who weren’t familiar with their
mathematical properties. More, they prevent the accumulation of distortions you
can expect while drawing manually with ruler and compass. More, girih tiles
allow to create constructions that are very difficult to construct by strapwork.
Starting from 1200 AC patterns of this type appear on Seljuk buildings.