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Rhombicuboctahedron
""Rhombicuboctahedron.jpg
""(Click here for rotating model)
Type "Archimedean solid
"Uniform polyhedron
"Elements F = 26, E = 48, V = 24 (χ = 2)
Faces by sides 8{3}+(6+12){4}
"Conway notation eC or aaC
aaaT
"Schläfli symbols rr{4,3} or
t0,2{4,3}
"Wythoff symbol 3 4 | 2
"Coxeter diagram CDel node 1.pngCDel 4.pngCDel node.pngCDel 3.pngCDel node 1.png
"Symmetry group "Oh, B3, [4,3], (*432), order 48
"Rotation group "O, [4,3]+, (432), order 24
"Dihedral angle 3-4: 144°44′08″ (144.74°)
4-4: 135°
"References "U10, "C22, "W13
Properties Semiregular "convex
""Small rhombicuboctahedron.png
Colored faces
""Small rhombicuboctahedron vertfig.png
3.4.4.4
("Vertex figure)
""Deltoidalicositetrahedron.jpg
"Deltoidal icositetrahedron
("dual polyhedron)
""Rhombicuboctahedron flat.png
"Net

In "geometry, the rhombicuboctahedron, or small rhombicuboctahedron, is an "Archimedean solid with eight "triangular and eighteen "square faces. There are 24 identical vertices, with one triangle and three squares meeting at each. (Note that six of the squares only share vertices with the triangles while the other twelve share an edge.) The "polyhedron has "octahedral symmetry, like the "cube and "octahedron. Its "dual is called the "deltoidal icositetrahedron or trapezoidal icositetrahedron, although its faces are not really true "trapezoids.

Contents

Names[edit]

"Johannes Kepler in "Harmonices Mundi (1618) named this polyhedron a rhombicuboctahedron, being short for truncated cuboctahedral rhombus, with cuboctahedral rhombus being his name for a "rhombic dodecahedron.[1] This truncation creates new vertices mid-edge to the rhombic dodecahedron, creating rectangular faces inside the original rhombic faces, and new square and triangle faces at the original vertices. The semiregular form here requires the geometry be adjusted so the rectangles become squares.

""Rhombic dodecahedron rectified to rhombicuboctahedron.png

It can also be called an "expanded cube or "cantellated cube or a cantellated octahedron from truncation operations of the "uniform polyhedron.

Geometric relations[edit]

""
""
The rhombicuboctahedron can be seen as either an "expanded cube (the blue faces) or an expanded "octahedron (the red faces).

There are distortions of the rhombicuboctahedron that, while some of the faces are not regular polygons, are still vertex-uniform. Some of these can be made by taking a cube or octahedron and cutting off the edges, then trimming the corners, so the resulting polyhedron has six square and twelve rectangular faces. These have octahedral symmetry and form a continuous series between the cube and the octahedron, analogous to the distortions of the "rhombicosidodecahedron or the tetrahedral distortions of the "cuboctahedron. However, the rhombicuboctahedron also has a second set of distortions with six rectangular and sixteen trapezoidal faces, which do not have octahedral symmetry but rather Th symmetry, so they are invariant under the same rotations as the "tetrahedron but different reflections.

The lines along which a "Rubik's Cube can be turned are, projected onto a sphere, similar, "topologically identical, to a rhombicuboctahedron's edges. In fact, variants using the Rubik's Cube mechanism have been produced which closely resemble the rhombicuboctahedron.[2][3]

The rhombicuboctahedron is used in three "uniform space-filling tessellations: the "cantellated cubic honeycomb, the "runcitruncated cubic honeycomb, and the "runcinated alternated cubic honeycomb.

Dissection[edit]

The rhombicuboctahedron can be dissected into two "square cupolae and a central "octagonal prism. A rotation of one cupola by 45 degrees creates the pseudo­rhombi­cubocta­hedron. Both of these polyhedra have the same vertex figure: 3.4.4.4.

There are three pairs of parallel planes that each intersect the rhombicuboctahedron in a regular octagon. The rhombicuboctahedron may be divided along any of these to obtain an octagonal prism with regular faces and two additional polyhedra called square "cupolae, which count among the "Johnson solids; it is thus an elongated square ortho"bicupola. These pieces can be reassembled to give a new solid called the "elongated square gyrobicupola or pseudorhombicuboctahedron, with the symmetry of a square antiprism. In this the vertices are all locally the same as those of a rhombicuboctahedron, with one triangle and three squares meeting at each, but are not all identical with respect to the entire polyhedron, since some are closer to the symmetry axis than others.

""Exploded rhombicuboctahedron.png ""Small rhombicuboctahedron.png
Rhombicuboctahedron
""Pseudorhombicuboctahedron.png
Pseudorhombicuboctahedron

Orthogonal projections[edit]

The rhombicuboctahedron has six special "orthogonal projections, centered, on a vertex, on two types of edges, and three types of faces: triangles, and two squares. The last two correspond to the B2 and A2 "Coxeter planes.

Orthogonal projections
Centered by Vertex Edge
3-4
Edge
4-4
Face
Square-1
Face
Square-2
Face
Triangle
Image ""Cube t02 v.png ""Cube t02 e34.png ""Cube t02 e44.png ""Cube t02 f4b.png ""3-cube t02 B2.svg ""3-cube t02.svg
Projective
symmetry
[2] [2] [2] [2] [4] [6]
Dual
image
""Dual cube t02 v.png ""Dual cube t02 e34.png ""Dual cube t02 e44.png ""Dual cube t02 f4b.png ""Dual cube t02 B2.png ""Dual cube t02.png

Spherical tiling[edit]

The rhombicuboctahedron can also be represented as a "spherical tiling, and projected onto the plane via a "stereographic projection. This projection is "conformal, preserving angles but not areas or lengths. Straight lines on the sphere are projected as circular arcs on the plane.

""Uniform tiling 432-t02.png ""Rhombicuboctahedron stereographic projection square.png
(6) "square-centered
""Rhombicuboctahedron stereographic projection square2.png
(6) "square-centered
""Rhombicuboctahedron stereographic projection triangle.png
(8) "triangle-centered
"Orthogonal projection "Stereographic projections

Pyritohedral symmetry[edit]

A half symmetry form of the rhombicuboctahedron, CDel node 1.pngCDel 3.pngCDel node.pngCDel 4.pngCDel node 1.png, exists with "pyritohedral symmetry, [4,3+], (3*2) as "Coxeter diagram CDel node h.pngCDel 3.pngCDel node h.pngCDel 4.pngCDel node 1.png, "Schläfli symbol s2{3,4}, and can be called a cantic snub octahedron. This form can be visualized by alternatingly coloring the edges of the 6 "squares. These squares can then be distorted into "rectangles, while the 8 triangles remain equilateral. The 12 diagonal square faces will become "isosceles trapezoids. In the limit, the rectangles can be reduced to edges, and the trapezoids become triangles, and an "icosahedron is formed, by a snub octahedron construction, CDel node h.pngCDel 3.pngCDel node h.pngCDel 4.pngCDel node.png, s{3,4}. the "compound of two icosahedra is constructed from both alternated positions.

Algebraic properties[edit]

Cartesian coordinates[edit]

"Cartesian coordinates for the vertices of a rhombicuboctahedron centred at the origin, with edge length 2 units, are all the "even permutations of

(±1, ±1, ±(1 + 2)).

If the original rhombicuboctahedron has unit edge length, its dual "strombic icositetrahedron has edge lengths

Area and volume[edit]

The area A and the volume V of the rhombicuboctahedron of edge length a are:

Close-packing density[edit]

The optimal "packing fraction of rhombicuboctahedra is given by

.

It was noticed that this optimal value is obtained in a "Bravais lattice by de Graaf (2011). Since the rhombicuboctahedron is contained in a "rhombic dodecahedron whose "inscribed sphere is identical to its own inscribed sphere, the value of the optimal packing fraction is a corollary of the "Kepler conjecture: it can be achieved by putting a rhombicuboctahedron in each cell of the "rhombic dodecahedral honeycomb, and it cannot be surpassed, since otherwise the optimal packing density of spheres could be surpassed by putting a sphere in each rhombicuboctahedron of the hypothetical packing which surpasses it.

In the arts[edit]

""Pacioli.jpg
Rhombicuboctahedron in top left of 1495 "Portrait of Luca Pacioli.[4]
""Leonardo polyhedra.png
"Leonardo da Vinci's illustration in "Divina Proportione, 1509: "Vigintisexbasium Planum Vacuum".[5]

The large polyhedron in the 1495 portrait of "Luca Pacioli, traditionally though controversially attributed to "Jacopo de' Barbari, is a glass rhombicuboctahedron half-filled with water. The first printed version of the rhombicuboctahedron was by "Leonardo da Vinci and appeared in his 1509 "Divina Proportione.

A spherical 180° × 360° panorama can be projected onto any polyhedron; but the rhombicuboctahedron provides a good enough approximation of a sphere while being easy to build. This type of projection, called Philosphere, is possible from some panorama assembly software. It consists of two images that are printed separately and cut with scissors while leaving some flaps for assembly with glue.[6]

Games and toys[edit]

""
""
"Rubik's Snake in a "ball solution: nonuniform concave rhombicuboctahedron.
""
""
A "Cabela's branded "self-healing" target made of ballistic material

The "Freescape games "Driller and "Dark Side both had a game map in the form of a rhombicuboctahedron.

The "Hurry-Scurry Galaxy" and "Sea Slide Galaxy" in the videogame "Super Mario Galaxy have planets in the similar shape of a rhombicuboctahedron.

"Sonic the Hedgehog 3's Icecap Zone features pillars topped with rhombicuboctahedra.

During the "Rubik's Cube craze of the 1980s, at least two twisty puzzles sold had the form of a rhombicuboctahedron (the mechanism was of course that of a "Rubik's Cube).[2][3]

The "Rubik's Snake toy (left) was usually sold in the shape of a stretched rhombicuboctahedron (12 of the squares being replaced with 1:2 rectangles).

One model of "Cabela's "Self healing ground bouncing reactive targets" (right), styled a sphere, resembles the rhombicuboctahedron.

Architecture[edit]

The building of "Belarus National Library has the shape of rhombicuboctahedron height of 72 meters.

""Park of National Library of Belarus.jpg

Related polyhedra[edit]

The rhombicuboctahedron is one of a family of uniform polyhedra related to the cube and regular octahedron.

Symmetry mutations[edit]

This polyhedron is topologically related as a part of sequence of "cantellated polyhedra with vertex figure (3.4.n.4), and continues as tilings of the "hyperbolic plane. These "vertex-transitive figures have (*n32) reflectional "symmetry.

Vertex arrangement[edit]

It shares its vertex arrangement with three "nonconvex uniform polyhedra: the "stellated truncated hexahedron, the "small rhombihexahedron (having the triangular faces and six square faces in common), and the "small cubicuboctahedron (having twelve square faces in common).

""Small rhombicuboctahedron.png
Rhombicuboctahedron
""Small cubicuboctahedron.png
"Small cubicuboctahedron
""Small rhombihexahedron.png
"Small rhombihexahedron
""Stellated truncated hexahedron.png
"Stellated truncated hexahedron

Rhombicuboctahedral graph[edit]

Rhombicuboctahedral graph
""Rhombicuboctahedral graph.png
4-fold symmetry
"Vertices 24
"Edges 48
"Automorphisms 48
Properties "Quartic graph, "Hamiltonian, "regular

In the "mathematical field of "graph theory, a rhombicuboctahedral graph is the "graph of vertices and edges of the rhombicuboctahedron, one of the "Archimedean solids. It has 24 "vertices and 48 edges, and is a "quartic graph "Archimedean graph.[7]

See also[edit]

Notes[edit]

  1. ^ Harmonies Of The World by Johannes Kepler, Translated into English with an introduction and notes by E. J. Aiton, A. M. Duncan, "J. V. Field, 1997, "ISBN "0-87169-209-0
  2. ^ a b "Soviet Puzzle Ball". TwistyPuzzles.com. Retrieved 23 December 2015. 
  3. ^ a b "Diamond Style Puzzler". Jaap's Puzzle Page. Retrieved 31 May 2017. 
  4. ^ RitrattoPacioli.it
  5. ^ Da divina proportione, page XXXVI
  6. ^ Philosphere
  7. ^ Read, R. C.; Wilson, R. J. (1998), An Atlas of Graphs, Oxford University Press, p. 269 

References[edit]

External links[edit]

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