dual pattern
Zooming in into the pattern, we can see that the broadened lines are built up by connecting square
and triangle units together. These bear a geometric pattern of 4-fold symmetry
(like the main pattern) we can reconstruct by an underlying pattern of blue
octagons, green squares and purple irregular pentagons on which the method of
constructing line patterns is applied.
A similar pattern Peter Cromwell finds on the shrine van sheik Ahmed-i Jan in Turbat-i Jan (1614). He draws it in his article Nexus Journal in 2016. The patroon uses the same forms and in it the broadened the broadened lines too are built up with squares, triangles and octagons. By rotating the squares by 45° the result is a pattern similar to the previous one, but just slightly different.
