This OpenSCAD script can generate variations on Oscar Reutersvärd's 1934 optical illusion. My approach was inspired by a picture of Artur Tchoukanov's model that I saw in the news (which in turn was inspired by Ulrich Schwanitz). Unfortunately, the news article didn't include the math behind the illusion's construction (they so rarely do!), so I had to rederive everything from scratch.Fortunately it took only a few minutes of basic geometry. This program demonstrates the math behind the illusion; it can generate triangles of arbitrary size and complexity.After some research, it seems that all these figures are in fact inspired by the work of Marcel Duchamp, who was producing impossible-figure photographs by playing with concavity/convexity as early as 1950. Duchamp's techniques are presented alongside the Reutersvärd illusion in this 2004 article: http://www.toutfait.com/online_journal_details.php?postid=1375I learn something new every day!Open the file in OpenSCAD and adjust the N, S, and T parameters. Remember to check your toolpaths before attempting to print -- this script will happily produce unprintable results if you're not careful!I'm hoping to improve printability so that I can use the N=2 version (middle image at left) as a part holder on my desk.