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A polycube is an orthogonal polyhedron composed of unit cubes glued together along entire faces, and homeomorphic to a sphere. A layer of a polycube refers to the portion lying between two horizontal cross-sections spaced one unit apart. We…

Computational Geometry · Computer Science 2025-07-15 Mirela Damian , Henk Meijer

We address the unsolved problem of unfolding prismatoids in a new context, viewing a "topless prismatoid" as a convex patch---a polyhedral subset of the surface of a convex polyhedron homeomorphic to a disk. We show that several natural…

Computational Geometry · Computer Science 2012-05-10 Joseph O'Rourke

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

We reprove a result of Dehkordi, Frati, and Gudmundsson: every two vertices in a non-obtuse triangulation of a point set are connected by an angle-monotone path--an xy-monotone path in an appropriately rotated coordinate system. We show…

Computational Geometry · Computer Science 2017-07-04 Anna Lubiw , 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

A straight-line drawing of a graph is a monotone drawing if for each pair of vertices there is a path which is monotonically increasing in some direction, and it is called a strongly monotone drawing if the direction of monotonicity is…

Computational Geometry · Computer Science 2016-01-08 Stefan Felsner , Alexander Igamberdiev , Philipp Kindermann , Boris Klemz , Tamara Mchedlidze , Manfred Scheucher

We investigate how to make the surface of a convex polyhedron (a polytope) by folding up a polygon and gluing its perimeter shut, and the reverse process of cutting open a polytope and unfolding it to a polygon. We explore basic enumeration…

Computational Geometry · Computer Science 2007-05-23 Erik D. Demaine , Martin L. Demaine , Anna Lubiw , Joseph O'Rourke

There exists a surface of a convex polyhedron P and a partition L of P into geodesic convex polygons such that there are no connected "edge" unfoldings of P without self-intersections (whose spanning tree is a subset of the edge skeleton of…

Computational Geometry · Computer Science 2008-10-06 Alexey S Tarasov

We consider drawings of trees in which all edges incident to leaves can be extended to infinite rays without crossing, partitioning the plane into infinite convex polygons. Among all such drawings we seek the one maximizing the angular…

Computational Geometry · Computer Science 2007-05-23 Josiah Carlson , David Eppstein

This paper presents a general framework for generating greedy algorithms for solving convex constraint satisfaction problems for sparse solutions by mapping the satisfaction problem into one of graph traversal on a rooted tree of unknown…

Data Structures and Algorithms · Computer Science 2015-09-16 Tarek A. Lahlou , Alan V. Oppenheim

In this work, we show the geometric properties of a family of polyhedra obtained by folding a regular tetrahedron along regular triangular grids. Each polyhedron is identified by a pair of nonnegative integers. The polyhedron can be cut…

Computational Geometry · Computer Science 2019-12-04 Seri Nishimoto , Takashi Horiyama , Tomohiro Tachi

Just how many different connected shapes result from slicing a cube along some of its edges and unfolding it into the plane? In this article we answer this question by viewing the cube both as a surface and as a graph of vertices and edges.…

Group Theory · Mathematics 2016-04-20 Richard Goldstone , Robert Suzzi Valli

Starting with the unsolved "D\"urer's problem" of edge-unfolding a convex polyhedron to a net, we specialize and generalize (a) the types of cuts permitted, and (b) the polyhedra shapes, to highlight both advances established and which…

Computational Geometry · Computer Science 2019-08-21 Joseph O'Rourke

Random geometric graphs result from taking $n$ uniformly distributed points in the unit cube, $[0,1]^d$, and connecting two points if their Euclidean distance is at most $r$, for some prescribed $r$. We show that monotone properties for…

Probability · Mathematics 2007-05-23 Ashish Goel , Sanatan Rai , Bhaskar Krishnamachari

We prove that any finite polyhedral manifold in 3D can be continuously flattened into 2D while preserving intrinsic distances and avoiding crossings, answering a 19-year-old open problem, if we extend standard folding models to allow for…

Computational Geometry · Computer Science 2021-05-25 Zachary Abel , Erik D. Demaine , Martin L. Demaine , Jason S. Ku , Jayson Lynch , Jin-ichi Itoh , Chie Nara

We prove two results about transforming any convex polyhedron, modeled as a linkage L of its edges. First, if we subdivide each edge of L in half, then L can be continuously flattened into a plane. Second, if L is equilateral and we again…

Computational Geometry · Computer Science 2024-12-20 Erik D. Demaine , Martin L. Demaine , Markus Hecher , Rebecca Lin , Victor H. Luo , Chie Nara

We define a new class of orthogonal polyhedra, called orthogrids, that can be unfolded without overlap with constant refinement of the gridded surface.

Computational Geometry · Computer Science 2013-10-18 Mirela Damian , Erik Demaine , Robin Flatland

A decision tree is commonly restricted to use a single hyperplane to split the covariate space at each of its internal nodes. It often requires a large number of nodes to achieve high accuracy, hurting its interpretability. In this paper,…

Machine Learning · Computer Science 2020-10-23 Mohammadreza Armandpour , Mingyuan Zhou

Tightness is a generalisation of the notion of convexity: a space is tight if and only if it is "as convex as possible", given its topological constraints. For a simplicial complex, deciding tightness has a straightforward exponential time…

Computational Geometry · Computer Science 2018-10-24 Bhaskar Bagchi , Benjamin A. Burton , Basudeb Datta , Nitin Singh , Jonathan Spreer

An unfolding of a polyhedron along its edges is called a vertex unfolding if adjacent faces are allowed to be connected at not only an edge but also a vertex. Demaine et al showed that every triangulated polyhedron has a vertex unfolding.…

Combinatorics · Mathematics 2013-02-19 Toshiki Endo , Yuki Suzuki