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Descartes, Euler, Poincaré, Pólya and Polyhedra Séminaire De Philosophie Et Mathématiques, 1982, Fascicule 8 « Descartes, Euler, Poincaré, Polya and Polyhedra », , P
Séminaire de philosophie et mathématiques PETER HILTON JEAN PEDERSEN Descartes, Euler, Poincaré, Pólya and Polyhedra Séminaire de Philosophie et Mathématiques, 1982, fascicule 8 « Descartes, Euler, Poincaré, Polya and Polyhedra », , p. 1-17 <http://www.numdam.org/item?id=SPHM_1982___8_A1_0> © École normale supérieure – IREM Paris Nord – École centrale des arts et manufactures, 1982, tous droits réservés. L’accès aux archives de la série « Séminaire de philosophie et mathématiques » implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/conditions). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright. Article numérisé dans le cadre du programme Numérisation de documents anciens mathématiques http://www.numdam.org/ - 1 - DESCARTES, EULER, POINCARÉ, PÓLYA—AND POLYHEDRA by Peter H i l t o n and Jean P e d e rs e n 1. Introduction When geometers talk of polyhedra, they restrict themselves to configurations, made up of vertices. edqes and faces, embedded in three-dimensional Euclidean space. Indeed. their polyhedra are always homeomorphic to thè two- dimensional sphere S1. Here we adopt thè topologists* terminology, wherein dimension is a topological invariant, intrinsic to thè configuration. and not a property of thè ambient space in which thè configuration is located. Thus S 2 is thè surface of thè 3-dimensional ball; and so we find. among thè geometers' polyhedra. thè five Platonic “solids”, together with many other examples. However. we should emphasize that we do not here think of a Platonic “solid” as a solid : we have in mind thè bounding surface of thè solid. -
Arxiv:2012.03250V2 [Math.LO] 26 May 2021
Axiomatizing origami planes L. Beklemishev1, A. Dmitrieva2, and J.A. Makowsky3 1Steklov Mathematical Institute of RAS, Moscow, Russia 1National Research University Higher School of Economics, Moscow 2University of Amsterdam, Amsterdam, The Netherlands 3Technion – Israel Institute of Technology, Haifa, Israel May 27, 2021 Abstract We provide a variant of an axiomatization of elementary geometry based on logical axioms in the spirit of Huzita–Justin axioms for the origami constructions. We isolate the fragments corresponding to nat- ural classes of origami constructions such as Pythagorean, Euclidean, and full origami constructions. The set of origami constructible points for each of the classes of constructions provides the minimal model of the corresponding set of logical axioms. Our axiomatizations are based on Wu’s axioms for orthogonal ge- ometry and some modifications of Huzita–Justin axioms. We work out bi-interpretations between these logical theories and theories of fields as described in J.A. Makowsky (2018). Using a theorem of M. Ziegler (1982) which implies that the first order theory of Vieta fields is unde- cidable, we conclude that the first order theory of our axiomatization of origami is also undecidable. arXiv:2012.03250v2 [math.LO] 26 May 2021 Dedicated to Professor Dick de Jongh on the occasion of his 81st birthday 1 1 Introduction The ancient art of paper folding, known in Japan and all over the world as origami, has a sufficiently long tradition in mathematics.1 The pioneering book by T. Sundara Rao [Rao17] on the science of paper folding attracted attention by Felix Klein. Adolf Hurwitz dedicated a few pages of his diaries to paper folding constructions such as the construction of the golden ratio and of the regular pentagon, see [Fri18]. -
Mathematics of Origami
Mathematics of Origami Angela Kohlhaas Loras College February 17, 2012 Introduction Origami ori + kami, “folding paper” Tools: one uncut square of paper, mountain and valley folds Goal: create art with elegance, balance, detail Outline History Applications Foldability Design History of Origami 105 A.D.: Invention of paper in China Paper-folding begins shortly after in China, Korea, Japan 800s: Japanese develop basic models for ceremonial folding 1200s: Origami globalized throughout Japan 1682: Earliest book to describe origami 1797: How to fold 1,000 cranes published 1954: Yoshizawa’s book formalizes a notational system 1940s-1960s: Origami popularized in the U.S. and throughout the world History of Origami Mathematics 1893: Geometric exercises in paper folding by Row 1936: Origami first analyzed according to axioms by Beloch 1989-present: Huzita-Hatori axioms Flat-folding theorems: Maekawa, Kawasaki, Justin, Hull TreeMaker designed by Lang Origami sekkei – “technical origami” Rigid origami Applications from the large to very small Miura-Ori Japanese solar sail “Eyeglass” space telescope Lawrence Livermore National Laboratory Science of the small Heart stents Titanium hydride printing DNA origami Protein-folding Two broad categories Foldability (discrete, computational complexity) Given a pattern of creases, when does the folded model lie flat? Design (geometry, optimization) How much detail can added to an origami model, and how efficiently can this be done? Flat-Foldability of Crease Patterns 훗 Three criteria for 훗: Continuity, Piecewise isometry, Noncrossing 2-Colorable Under the mapping 훗, some faces are flipped while others are only translated and rotated. Maekawa-Justin Theorem At any interior vertex, the number of mountain and valley folds differ by two. -
A Technology to Synthesize 360-Degree Video Based on Regular Dodecahedron in Virtual Environment Systems*
A Technology to Synthesize 360-Degree Video Based on Regular Dodecahedron in Virtual Environment Systems* Petr Timokhin 1[0000-0002-0718-1436], Mikhail Mikhaylyuk2[0000-0002-7793-080X], and Klim Panteley3[0000-0001-9281-2396] Federal State Institution «Scientific Research Institute for System Analysis of the Russian Academy of Sciences», Moscow, Russia 1 [email protected], 2 [email protected], 3 [email protected] Abstract. The paper proposes a new technology of creating panoramic video with a 360-degree view based on virtual environment projection on regular do- decahedron. The key idea consists in constructing of inner dodecahedron surface (observed by the viewer) composed of virtual environment snapshots obtained by twelve identical virtual cameras. A method to calculate such cameras’ projec- tion and orientation parameters based on “golden rectangles” geometry as well as a method to calculate snapshots position around the observer ensuring synthe- sis of continuous 360-panorama are developed. The technology and the methods were implemented in software complex and tested on the task of virtual observing the Earth from space. The research findings can be applied in virtual environment systems, video simulators, scientific visualization, virtual laboratories, etc. Keywords: Visualization, Virtual Environment, Regular Dodecahedron, Video 360, Panoramic Mapping, GPU. 1 Introduction In modern human activities the importance of the visualization of virtual prototypes of real objects and phenomena is increasingly grown. In particular, it’s especially required for training specialists in space and aviation industries, medicine, nuclear industry and other areas, where the mistake cost is extremely high [1-3]. The effectiveness of work- ing with virtual prototypes is significantly increased if an observer experiences a feeling of being present in virtual environment. -
Cones, Pyramids and Spheres
The Improving Mathematics Education in Schools (TIMES) Project MEASUREMENT AND GEOMETRY Module 12 CONES, PYRAMIDS AND SPHERES A guide for teachers - Years 9–10 June 2011 YEARS 910 Cones, Pyramids and Spheres (Measurement and Geometry : Module 12) For teachers of Primary and Secondary Mathematics 510 Cover design, Layout design and Typesetting by Claire Ho The Improving Mathematics Education in Schools (TIMES) Project 2009‑2011 was funded by the Australian Government Department of Education, Employment and Workplace Relations. The views expressed here are those of the author and do not necessarily represent the views of the Australian Government Department of Education, Employment and Workplace Relations. © The University of Melbourne on behalf of the International Centre of Excellence for Education in Mathematics (ICE‑EM), the education division of the Australian Mathematical Sciences Institute (AMSI), 2010 (except where otherwise indicated). This work is licensed under the Creative Commons Attribution‑NonCommercial‑NoDerivs 3.0 Unported License. 2011. http://creativecommons.org/licenses/by‑nc‑nd/3.0/ The Improving Mathematics Education in Schools (TIMES) Project MEASUREMENT AND GEOMETRY Module 12 CONES, PYRAMIDS AND SPHERES A guide for teachers - Years 9–10 June 2011 Peter Brown Michael Evans David Hunt Janine McIntosh Bill Pender Jacqui Ramagge YEARS 910 {4} A guide for teachers CONES, PYRAMIDS AND SPHERES ASSUMED KNOWLEDGE • Familiarity with calculating the areas of the standard plane figures including circles. • Familiarity with calculating the volume of a prism and a cylinder. • Familiarity with calculating the surface area of a prism. • Facility with visualizing and sketching simple three‑dimensional shapes. • Facility with using Pythagoras’ theorem. • Facility with rounding numbers to a given number of decimal places or significant figures. -
Polyhedral Surfaces, Discrete Curvatures, Shape Analysis, 3D Modelling, Segmentation
JOURNAL OF MEDICAL INFORMATICS & TECHNOLOGIES Vol. 9/2005, ISSN 1642-6037 polyhedral surfaces, discrete curvatures, shape analysis, 3D modelling, segmentation. Alexandra BAC, Marc DANIEL, Jean-Louis MALTRET* 3D MODELLING AND SEGMENTATION WITH DISCRETE CURVATURES Recent concepts of discrete curvatures are very important for Medical and Computer Aided Geometric Design applications. A first reason is the opportunity to handle a discretisation of a continuous object, with a free choice of the discretisation. A second and most important reason is the possibility to define second-order estimators for discrete objects in order to estimate local shapes and manipulate discrete objects. There is an increasing need to handle polyhedral objects and clouds of points for which only a discrete approach makes sense. These sets of points, once structured (in general meshed with simplexes for surfaces or volumes), can be analysed using these second-order estimators. After a general presentation of the problem, a first approach based on angular defect, is studied. Then, a local approximation approach (mostly by quadrics) is presented. Different possible applications of these techniques are suggested, including the analysis of 2D or 3D images, decimation, segmentation... We finally emphasise different artefacts encountered in the discrete case. 1. INTRODUCTION This paper offers a review of work on discrete curvatures for Computer Aided Geometric Design applications and a discussion about some ideas for further studies. We consider the discrete curvatures computed on a set of points and their relevance to continuous curvatures when the density of the points increases. First of all, it is interesting to recall that curvatures are fundamental tools for studying curves and surfaces. -
Deepdt: Learning Geometry from Delaunay Triangulation for Surface Reconstruction
The Thirty-Fifth AAAI Conference on Artificial Intelligence (AAAI-21) DeepDT: Learning Geometry From Delaunay Triangulation for Surface Reconstruction Yiming Luo †, Zhenxing Mi †, Wenbing Tao* National Key Laboratory of Science and Technology on Multi-spectral Information Processing School of Artifical Intelligence and Automation, Huazhong University of Science and Technology, China yiming [email protected], [email protected], [email protected] Abstract in In this paper, a novel learning-based network, named DeepDT, is proposed to reconstruct the surface from Delau- Ray nay triangulation of point cloud. DeepDT learns to predict Camera Center inside/outside labels of Delaunay tetrahedrons directly from Point a point cloud and corresponding Delaunay triangulation. The out local geometry features are first extracted from the input point (a) (b) cloud and aggregated into a graph deriving from the Delau- nay triangulation. Then a graph filtering is applied on the ag- gregated features in order to add structural regularization to Figure 1: A 2D example of reconstructing surface by in/out the label prediction of tetrahedrons. Due to the complicated labeling of tetrahedrons. The visibility information is inte- spatial relations between tetrahedrons and the triangles, it is grated into each tetrahedron by intersections between view- impossible to directly generate ground truth labels of tetra- hedrons from ground truth surface. Therefore, we propose a ing rays and tetrahedrons. A graph cuts optimization is ap- multi-label supervision strategy which votes for the label of plied to classify tetrahedrons as inside or outside the sur- a tetrahedron with labels of sampling locations inside it. The face. Result surface is reconstructed by extracting triangular proposed DeepDT can maintain abundant geometry details facets between tetrahedrons of different labels. -
Open Problems from CCCG 2006
CCCG 2007, Ottawa, Ontario, August 20–22, 2007 Open Problems from CCCG 2006 Erik D. Demaine∗ Joseph O’Rourke† The following is a list of the problems presented on between any two unit-length 3D trees of the same August 14, 2006 at the open-problem session of the 18th number of links using edge reconnections? Canadian Conference on Computational Geometry held in Kingston, Ontario, Canada. Update: At the conference, a related move was Edge Reconnections in Unit Chains defined: a tetrahedral swap alters consecutive ver- Anna Lubiw tices (a, b, c, d) of a chain to either (a, c, b, d) or University of Waterloo (a, d, b, c), whichever of the two yields a chain. It [email protected] was established (by Erik Demaine, Anna Lubiw, and Joseph O’Rourke) that, if tetrahedral swaps Is it possible to reconfigure between any two con- are permitted without regard to self-intersection, figurations of a unit-length 3D polygonal chain, or then they suffice to unlock any chain. more generally unit-length 3D polygonal trees, by “edge reconnections”? Edge Swaps in Planar Matchings Ferran Hurtado (via Henk Meijer) a Univ. Polit´ecnicade Catalunya [email protected] b Is the space of (noncrossing) plane matchings on (a) c a set of n points in general position connected by “two-edge swaps”? A two-edge swap replaces two edges ab and cd of a plane matching M with a dif- ferent pair of edges on the same vertices, say ac and bd, to form another plane matching M 0. (The swap is valid only if the resulting matching is non- crossing.) Notice that ac and bd together with their a c a=c c replacement edges form a length-4 alternating cycle that does not cross any segments in M. -
Constructing Points Through Folding and Intersection
CONSTRUCTING POINTS THROUGH FOLDING AND INTERSECTION The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Butler, Steve, Erik Demaine, Ron Graham and Tomohiro Tachi. "Constructing points through folding and intersection." International Journal of Computational Geometry & Applications, Vol. 23 (01) 2016: 49-64. As Published 10.1142/S0218195913500039 Publisher World Scientific Pub Co Pte Lt Version Author's final manuscript Citable link https://hdl.handle.net/1721.1/121356 Terms of Use Creative Commons Attribution-Noncommercial-Share Alike Detailed Terms http://creativecommons.org/licenses/by-nc-sa/4.0/ Constructing points through folding and intersection Steve Butler∗ Erik Demaine† Ron Graham‡ Tomohiro Tachi§ Abstract Fix an n 3. Consider the following two operations: given a line with a specified point on the line we≥ can construct a new line through the point which forms an angle with the new line which is a multiple of π/n (folding); and given two lines we can construct the point where they cross (intersection). Starting with the line y = 0 and the points (0, 0) and (1, 0) we determine which points in the plane can be constructed using only these two operations for n =3, 4, 5, 6, 8, 10, 12, 24 and also consider the problem of the minimum number of steps it takes to construct such a point. 1 Introduction If an origami model is laid flat the piece of paper will retain a memory of the folds that went into the construction of the model as creases (or lines) in the paper. -
Folding a Paper Strip to Minimize Thickness✩
Folding a Paper Strip to Minimize Thickness✩ Erik D. Demainea, David Eppsteinb, Adam Hesterbergc, Hiro Itod, Anna Lubiwe, Ryuhei Ueharaf, Yushi Unog aComputer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge, USA bComputer Science Department, University of California, Irvine, USA cDepartment of Mathematics, Massachusetts Institute of Technology, USA dSchool of Informatics and Engineering, University of Electro-Communications, Tokyo, Japan eDavid R. Cheriton School of Computer Science, University of Waterloo, Ontario, Canada fSchool of Information Science, Japan Advanced Institute of Science and Technology, Ishikawa, Japan gGraduate School of Science, Osaka Prefecture University, Osaka, Japan Abstract In this paper, we study how to fold a specified origami crease pattern in order to minimize the impact of paper thickness. Specifically, origami designs are often expressed by a mountain-valley pattern (plane graph of creases with relative fold orientations), but in general this specification is consistent with exponentially many possible folded states. We analyze the complexity of finding the best consistent folded state according to two metrics: minimizing the total number of layers in the folded state (so that a “flat folding” is indeed close to flat), and minimizing the total amount of paper required to execute the folding (where “thicker” creases consume more paper). We prove both problems strongly NP- complete even for 1D folding. On the other hand, we prove both problems fixed-parameter tractable in 1D with respect to the number of layers. Keywords: linkage, NP-complete, optimization problem, rigid origami. 1. Introduction Most results in computational origami design assume an idealized, zero- thickness piece of paper. This approach has been highly successful, revolution- izing artistic origami over the past few decades. -
Constructing Points Through Folding and Intersection
Constructing points through folding and intersection Steve Butler∗ Erik Demaine† Ron Graham‡ Tomohiro Tachi§ Abstract Fix an n 3. Consider the following two operations: given a line with a specified point on the line we≥ can construct a new line through the point which forms an angle with the new line which is a multiple of π/n (folding); and given two lines we can construct the point where they cross (intersection). Starting with the line y = 0 and the points (0, 0) and (1, 0) we determine which points in the plane can be constructed using only these two operations for n =3, 4, 5, 6, 8, 10, 12, 24 and also consider the problem of the minimum number of steps it takes to construct such a point. 1 Introduction If an origami model is laid flat the piece of paper will retain a memory of the folds that went into the construction of the model as creases (or lines) in the paper. These creases will sometimes be reflected as places in the final model where the paper is bent and sometimes will be left over artifacts from early in the construction process. These creases can also be used in the construction of reference points, which play a useful role in the design of complicated origami models (see [6]). As such, tools to help efficiently construct reference points have been developed, i.e., ReferenceFinder [7]. The problem of finding which points can be constructed using origami has been extensively studied. In particular, using the Huzita-Hatori axioms it has been shown that all quartic polyno- mials can be solved using origami (see [4, pp. -
Binding Regular Polyhedra
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repository of the Academy's Library Optimal packages: binding regular polyhedra F. Kovacs´ Department of Structural Mechanics Budapest University of Technology and Economics ABSTRACT: Strings on the surface of gift boxes can be modelled as a special kind of cable-and-joint struc- ture. This paper deals with systems composed of idealised (frictionless) closed loops of strings that provide stable binding to the underlying convex polyhedron (‘package’). Optima are searched in both the sense of topology and geometry in finding minimal number of closed loops as well as the minimal (total) length of cables to ensure such a stable binding for simple cases of polyhedra. 1 INTRODUCTION and concave otherwise (for example, ‘zigzag’ loops with alternating turns are concave). In these terms, the 1.1 Loops on a polyhedral surface loop on the left hand side of Fig. 1 is complex due to the self-intersection at the top and concave because of There are some practical occurrences of closed strings the two rectangular turns with different handedness on polyhedral surfaces. For example, mailed pack- at the bottom (such connections will be called self- ages are traditionally bound by some pieces of string. binding from now on); whereas the skew string to the Another example is from basketry, when a woven right is simple and convex (by having no turns within pattern over a polyhedral surface is also formed by the polyhedral surface at all). some (mainly closed) strings (Tarnai, Kov´acs, Fowler, & Guest 2012, Kov´acs 2014).