Here is a handcoded SVG version of Template A, which appears on p. 11 of Eric Broug’s book Islamic Geometric Patterns.
This pattern has 6 contruction lines, and 12 equal parts.
Per Broug, it is the first of three major families of Islamic pattern building blocks; these are based on four (A), five (B), or six (C) interlacing circles centered around a primary circle.
I more of less followed the steps outlined on pp. 10-11 in Patterns, but skipped Step 5 which I found superfluous.
During this exercise, I loaded my code into Inkscape to guess-timate the coordinates of some of the straight line endpoints. Then it was a matter of crude, trial-and-error values for the x and z attributes of the line elements to get it “pixel perfect.”
But if you look closely at the result, you might notice that this pattern contains 4 “pyramids” or triangles, connected perpendicularly at the top.
I’ll use this observation to calculate a second set of endpoints for the angled straight lines of Template A, and verify that these new lines cross the underlying interlacing circles at the same points.
If they do not, two questions arise:
- What is the geometric reason for this?
- What are the implications going forward for our SVG library of Islamic patterns?
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