Face flips in origami tessellations
Abstract
Given a flatfoldable origami crease pattern $G=(V,E)$ (a straightline drawing of a planar graph on a region of the plane) with a mountainvalley (MV) assignment $\mu:E\to\{1,1\}$ indicating which creases in $E$ bend convexly (mountain) or concavely (valley), we may \emph{flip} a face $F$ of $G$ to create a new MV assignment $\mu_F$ which equals $\mu$ except for all creases $e$ bordering $F$, where we have $\mu_F(e)=\mu(e)$. In this paper we explore the configuration space of face flips for a variety of crease patterns $G$ that are tilings of the plane, proving examples where $\mu_F$ results in a MV assignment that is either never, sometimes, or always flatfoldable for various choices of $F$. We also consider the problem of finding, given two foldable MV assignments $\mu_1$ and $\mu_2$ of a given crease pattern $G$, a minimal sequence of face flips to turn $\mu_1$ into $\mu_2$. We find polynomialtime algorithms for this in the cases where $G$ is either a square grid or the Miuraori, and show that this problem is NPhard in the case where $G$ is the triangle lattice.
 Publication:

arXiv eprints
 Pub Date:
 October 2019
 arXiv:
 arXiv:1910.05667
 Bibcode:
 2019arXiv191005667A
 Keywords:

 Mathematics  Combinatorics;
 Computer Science  Computational Geometry;
 52C45;
 68U05