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There are two known ways to unfold a convex polyhedron without overlap: the star unfolding and the source unfolding, both of which use shortest paths from vertices to a source point on the surface of the polyhedron. Non-overlap of the source unfolding is straightforward; non-overlap of the star unfolding was proved by Aronov and O'Rourke in 1992. Our first contribution is a much simpler proof of non-overlap of the star unfolding. Both the source and star unfolding can be generalized to use a simple geodesic curve instead of a source point. The star unfolding from a geodesic curve cuts the geodesic curve and a shortest path from each vertex to the geodesic curve. Demaine and Lubiw conjectured that the star unfolding from a geodesic curve does not overlap. We prove a special case of the conjecture. Our special case includes the previously known case of unfolding from a geodesic loop. For the general case we prove that the star unfolding from a geodesic curve can be separated into at most two non-overlapping pieces.
@InProceedings{kiazyk_et_al:LIPIcs.SOCG.2015.390,
author = {Kiazyk, Stephen and Lubiw, Anna},
title = {{Star Unfolding from a Geodesic Curve}},
booktitle = {31st International Symposium on Computational Geometry (SoCG 2015)},
pages = {390--404},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-939897-83-5},
ISSN = {1868-8969},
year = {2015},
volume = {34},
editor = {Arge, Lars and Pach, J\'{a}nos},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SOCG.2015.390},
URN = {urn:nbn:de:0030-drops-51380},
doi = {10.4230/LIPIcs.SOCG.2015.390},
annote = {Keywords: unfolding, convex polyhedra, geodesic curve}
}