Iterations of the Dragon Curve

Various properties of finite iterations of the Heighway/Harter dragon curve and twindragon curve, including boundary, area, convex hull, minimum rectangle, XY convex hull, centroid, inertia, complex base i±1, area tree, and fractionals including boundary and fixed point.

A sample dragon curve image (about 2.4 kbytes).

Read draft 17,

PDF dragon.pdf (about 3.1 mbytes, 344 pages)
LaTeX source dragon-17.tar.gz (about 2.8 mbytes, and sig)

Also by plain HTTP or by FTP or by RSYNC if desired. The sig file is a Gnu PG ascii armoured signature generated from my key.

"Draft" here means otherwise believed correct as far as it goes but with some more to be added. Sections and equations will renumber. The quality varies in places, and it's becoming quite long, but there's plenty of pictures to look at. The LaTeX source uses PGF for pictures.

Draft 16 had a typo in the fLpred statement and errors in fR etc formulas and sample values.

Document copyright 2014, 2015, 2016, 2017, 2018, 2019 Kevin Ryde. Permission is granted for anyone to make a copy for the purpose of reading it. The PDF rendition contains fonts which are Copyright American Mathematical Society and licensed under the open font license.

The source .tar.gz includes various generator and development programs which are all GPLv3 up. They're mostly Perl and a bit rough. Modules used variously include FLAT, Graph, and Math::Geometry::Planar (some debs in my repo). The document has self-tests with Pari/GP and gp-inline. GP functions are extracted to a devel/dragon-defines.gp which is highly specific to the document but might be of interest for experimenting. (Needs at least GP 2.9 up for various things.) Some C code using the Nauty library makes dragon curve graphs and trees for experimenting.

Here are some dragon curve drawing programs by me and variously posted on Rosetta Code. The algorithms vary with the strengths of each language. (Between 2 and 6 kbytes each, all free software GPLv3 up, included in the .tar.gz above.)