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We show how to edge-unfold a new class of convex polyhedra, specifically a new class of prismatoids (the convex hull of two parallel convex polygons, called the top and base), by constructing a nonoverlapping "petal unfolding" in two new…

Computational Geometry · Computer Science 2021-06-29 Vincent Bian , Erik Demaine , Rachana Madhukara

A notion of "radially monotone" cut paths is introduced as an effective choice for finding a non-overlapping edge-unfolding of a convex polyhedron. These paths have the property that the two sides of the cut avoid overlap locally as the cut…

Computational Geometry · Computer Science 2016-08-01 Joseph O'Rourke

We prove that, for any two polyhedral manifolds $\mathcal P,\mathcal Q$, there is a polyhedral manifold $\mathcal I$ such that $\mathcal P,\mathcal I$ share a common unfolding and $\mathcal I,\mathcal Q$ share a common unfolding. In other…

Computational Geometry · Computer Science 2025-11-18 Lily Chung , Erik D. Demaine , Jenny Diomidova , Tonan Kamata , Jayson Lynch , Ryuhei Uehara , Hanyu Alice Zhang

We prove that, for any two polyhedral manifolds $\mathcal P, \mathcal Q$, there is a polyhedral manifold $\mathcal I$ such that $\mathcal P, \mathcal I$ share a common unfolding and $\mathcal I,\mathcal Q$ share a common unfolding. In other…

Computational Geometry · Computer Science 2025-10-08 Lily Chung , Erik D. Demaine , Jenny Diomidova , Tonan Kamata , Jayson Lynch , Ryuhei Uehara , Hanyu Alice Zhang

This paper studies the straight skeleton of polyhedra in three dimensions. We first address voxel-based polyhedra (polycubes), formed as the union of a collection of cubical (axis-aligned) voxels. We analyze the ways in which the skeleton…

Computational Geometry · Computer Science 2008-05-02 Gill Barequet , David Eppstein , Michael T. Goodrich , Amir Vaxman

An unzipping of a polyhedron P is a cut-path through its vertices that unfolds P to a non-overlapping shape in the plane. It is an open problem to decide if every convex P has an unzipping. Here we show that there are nearly flat convex…

Computational Geometry · Computer Science 2018-02-07 Joseph O'Rourke

It is shown that there are examples of distinct polyhedra, each with a Hamiltonian path of edges, which when cut, unfolds the surfaces to a common net. In particular, it is established for infinite classes of triples of tetrahedra.

Computational Geometry · Computer Science 2011-06-09 Joseph O'Rourke

We define a notion for unfolding smooth, ruled surfaces, and prove that every smooth prismatoid (the convex hull of two smooth curves lying in parallel planes), has a nonoverlapping "volcano unfolding." These unfoldings keep the base…

Computational Geometry · Computer Science 2015-03-12 Nadia Benbernou , Patricia Cahn , Joseph O'Rourke

A convex polyhedron, that is, a compact convex subset of $\mathbb{R}^3$ which is the intersection of finitely many closed half-spaces, can be rectified by taking the convex hull of the midpoints of the edges of the polyhedron. We derive…

Metric Geometry · Mathematics 2016-04-05 Samuel Reid

In this work we study inside-out dissections of polygons and polyhedra. We first show that an arbitrary polygon can be inside-out dissected with $2n+1$ pieces, thereby improving the best previous upper bound of $4(n-2)$ pieces.…

Computational Geometry · Computer Science 2024-11-12 Reymond Akpanya , Adi Rivkin , Frederick Stock

We describe a polynomial time algorithm that takes as input a polygon with axis-parallel sides but irrational vertex coordinates, and outputs a set of as few rectangles as possible into which it can be dissected by axis-parallel cuts and…

Computational Geometry · Computer Science 2025-01-08 David Eppstein

It is well known that a three dimensional (closed, connected and compact) manifold is obtained by identifying boundary faces from a polyhedron P. The study of (\partial P)/~, the boundary \partial P with the polygonal faces identified in…

General Mathematics · Mathematics 2007-05-23 Sergey Nikitin

A polyiamond is a polygon composed of unit equilateral triangles, and a generalized deltahedron is a convex polyhedron whose every face is a convex polyiamond. We study a variant where one face may be an exception. For a convex polygon P,…

Consider an orthogonal polyhedron, i.e., a polyhedron where (at least after a suitable rotation) all faces are perpendicular to a coordinate axis, and hence all edges are parallel to a coordinate axis. Clearly, any facial angle and any…

Computational Geometry · Computer Science 2013-12-25 Therese Biedl , Martin Derka , Stephen Kiazyk , Anna Lubiw , Hamide Vosoughpour

Given a convex polyhedral surface P, we define a tailoring as excising from P a simple polygonal domain that contains one vertex v, and whose boundary can be sutured closed to a new convex polyhedron via Alexandrov's Gluing Theorem. In…

Metric Geometry · Mathematics 2022-05-24 Joseph O'Rourke , Costin Vilcu

A convex polyhedron $P$ is $k$-equiprojective if all of its orthogonal projections, i.e., shadows, except those parallel to the faces of $P$ are $k$-gon for some fixed value of $k$. Since 1968, it is an open problem to construct all…

Computational Geometry · Computer Science 2010-09-14 Masud Hasan , Mohammad Monoar Hossain , Alejandro López-Ortiz , Sabrina Nusrat , Saad Altaful Quader , Nabila Rahman

We give a complete description of all convex polyhedra whose surface can be constructed from several congruent regular pentagons by folding and gluing them edge to edge. Our method of determining the graph structure of the polyhedra from a…

Computational Geometry · Computer Science 2020-07-06 Elena Arseneva , Stefan Langerman , Boris Zolotov

Two tetrahedra are called orthologic if the lines through vertices of one and perpendicular to corresponding faces of the other are intersecting. This is equivalent to the orthogonality of non-corresponding edges. We prove that the…

Metric Geometry · Mathematics 2012-05-10 Hans-Peter Schröcker

An orthotube consists of orthogonal boxes (e.g., unit cubes) glued face-to-face to form a path. In 1998, Biedl et al. showed that every orthotube has a grid unfolding: a cutting along edges of the boxes so that the surface unfolds into a…

Computational Geometry · Computer Science 2023-05-02 Erik D. Demaine , Kritkorn Karntikoon

Given any two convex polyhedra P and Q, we prove as one of our main results that the surface of P can be reshaped to a homothet of Q by a finite sequence of "tailoring" steps. Each tailoring excises a digon surrounding a single vertex and…

Metric Geometry · Mathematics 2020-08-06 Joseph O'Rourke , Costin Vilcu