Journal of Information Processing
Online ISSN : 1882-6652
ISSN-L : 1882-6652
Simple Folding is Really Hard
Hugo A. AkitayaErik D. DemaineJason S. Ku
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2017 Volume 25 Pages 580-589


Simple folding (folding along one line at a time) is a practical form of origami used in manufacturing such as sheet metal bending. We prove strong NP-completeness of deciding whether a crease pattern can be simply folded, both for orthogonal paper with assigned orthogonal creases and for square paper with assigned or unassigned creases at multiples of 45°. These results settle a long standing open problem, where weak NP-hardness was established for a subset of the models considered here, leaving open the possibility of pseudopolynomial-time algorithms. We also formalize and generalize the previously proposed simple folding models, and introduce new infinite simple-fold models motivated by practical manufacturing. In the infinite models, we extend our strong NP-hardness results, as well as polynomial-time algorithms for rectangular paper with assigned or unassigned orthogonal creases (map folding). These results motivate why rectangular maps have orthogonal but not diagonal creases.

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© 2017 by the Information Processing Society of Japan
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