Chamfer (geometry)

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Polyhedron 6 unchamfered.png
Polyhedron 6 slightly chamfered.png
Polyhedron chamfered 6 edeq.png
Unchamfered, slightly chamfered, and chamfered cube
Modell, Kristallform Tetraeder-Tetraeder -Krantz 394-.jpg
Modell, Kristallform Wurfel-Rhombendodekaeder -Krantz 428-.jpg
Modell, Kristallform Oktaeder-Rhombendodekaeder -Krantz 432-.jpg
Historical crystal models of slightly chamfered Platonic solids

In geometry, chamfering or edge-truncation is a topological operator that modifies one polyhedron into another. It is similar to expansion: it moves the faces apart (outward), and adds a new face between each two adjacent faces; but contrary to expansion, it maintains the original vertices. (Equivalently: it separates the faces by reducing them, and adds a new face between each two adjacent faces; but it only moves the vertices lower.) For a polyhedron, this operation adds a new hexagonal face in place of each original edge.

Contents

In Conway polyhedron notation, chamfering is represented by the letter "c". A polyhedron with e edges will have a chamfered form containing 2e new vertices, 3e new edges, and e new hexagonal faces.

Chamfered Platonic solids

In the chapters below, the chamfers of the five Platonic solids are described in detail. Each is shown in a version with edges of equal lengths, and in a canonical version where all edges touch the same midsphere. (They look noticeably different only for solids containing triangles.) The shown dual polyhedra are dual to the canonical versions.

Seed
Platonic
solid
Polyhedron 4a.png Polyhedron 4b.png
{3,3}
Polyhedron 6.png
{4,3}
Polyhedron 8.png
{3,4}
Polyhedron 12.png
{5,3}
Polyhedron 20.png
{3,5}
Chamfered
Platonic
solid
Polyhedron chamfered 4a edeq.png Polyhedron chamfered 4b edeq.png Polyhedron chamfered 6 edeq.png Polyhedron chamfered 8 edeq.png Polyhedron chamfered 12 edeq.png Polyhedron chamfered 20 edeq.png

Chamfered tetrahedron

Chamfered tetrahedron
Polyhedron chamfered 4a edeq max.png
(equilateral-faced form)
Conway notation cT
Goldberg polyhedron GPIII(2,0) = {3+,3}2,0
Faces4 congruent equilateral triangles
6 congruent hexagons (equilateral for a certain chamfering depth)
Edges24 (2 types:
triangle-hexagon,
hexagon-hexagon)
Vertices16 (2 types)
Vertex configuration (12) 3.6.6
(4) 6.6.6
Symmetry group Tetrahedral (Td)
Dual polyhedron Alternate-triakis tetratetrahedron
Properties convex, equilateral-faced (for a certain chamfering depth)
Polyhedron chamfered 4a net.svg
Net

The chamfered tetrahedron (or alternate truncated cube) is a convex polyhedron constructed by alternately truncating a cube, replacing 4 of its 8 vertices with congruent triangular faces, or by chamfering a regular tetrahedron, replacing its 6 edges with congruent flattened hexagons.

The chamfered tetrahedron is the Goldberg polyhedron GIII(2,0), containing triangular and hexagonal faces.

The truncated tetrahedron looks similar; but its hexagons correspond to the 4 faces, not to the 6 edges, of the yellow tetrahedron, i.e. to the 4 vertices, not to the 6 edges, of the red tetrahedron. Polyhedron truncated 4b max.png
The truncated tetrahedron looks similar; but its hexagons correspond to the 4 faces, not to the 6 edges, of the yellow tetrahedron, i.e. to the 4 vertices, not to the 6 edges, of the red tetrahedron.
Historical drawings of truncated tetrahedron and slightly chamfered tetrahedron. EB1911 Crystallography Figs. 30 & 31.jpg
Historical drawings of truncated tetrahedron and slightly chamfered tetrahedron.
Tetrahedral chamfers and their duals
Polyhedron chamfered 4a.png
chamfered tetrahedron (canonical form)
Polyhedron 4-4 dual.png
dual of the tetratetrahedron
Polyhedron chamfered 4b.png
chamfered tetrahedron (canonical form)
Polyhedron chamfered 4a dual.png
alternate-triakis tetratetrahedron
Polyhedron 4-4.png
tetratetrahedron
Polyhedron chamfered 4b dual.png
alternate-triakis tetratetrahedron

Chamfered cube

Chamfered cube
Polyhedron chamfered 6 edeq max.png
(equilateral-faced form)
Conway notation cC = t4daC
Goldberg polyhedron GPIV(2,0) = {4+,3}2,0
Faces6 congruent squares
12 congruent hexagons (equilateral for a certain chamfering depth)
Edges48 (2 types:
square-hexagon,
hexagon-hexagon)
Vertices32 (2 types)
Vertex configuration (24) 4.6.6
(8) 6.6.6
Symmetry Oh, [4,3], (*432)
Th, [4,3+], (3*2)
Dual polyhedron Tetrakis cuboctahedron
Properties convex, equilateral-faced (for a certain chamfering depth)
Truncated rhombic dodecahedron net.png
Net (3 zones are shown by 3 colors for their hexagons — each square is in 2 zones —.)

The chamfered cube is constructed as a chamfer of a cube: the squares are reduced in size and new hexagonal faces are added in place of all the original edges. The chamfered cube is a convex polyhedron with 32 vertices, 48 edges, and 18 faces: 6 congruent (and regular) squares, and 12 congruent flattened hexagons which are equilateral for a certain depth of chamfering. Its dual is the tetrakis cuboctahedron.

It is also inaccurately called a truncated rhombic dodecahedron, although that name rather suggests a rhombicuboctahedron. It can more accurately be called a tetratruncated rhombic dodecahedron, because only the (6) order-4 vertices of the rhombic dodecahedron are truncated.

The hexagonal faces are equilateral but not regular. They are congruent partly truncated rhombi, have 2 internal angles of and 4 internal angles of while a regular hexagon would have all internal angles.

Because all its faces have an even number of sides and are centrally symmetric, it is a zonohedron. It is also the Goldberg polyhedron GPIV(2,0) or {4+,3}2,0, containing square and hexagonal faces.

The chamfered cube is the Minkowski sum of a rhombic dodecahedron and a cube of side length 1 when the eight order-3 vertices of the rhombic dodecahedron are at and its six order-4 vertices are at the permutations of

A topological equivalent with pyritohedral symmetry and rectangular faces can be constructed by chamfering the axial edges of a pyritohedron. This occurs in pyrite crystals.

Polyhedron pyritohedron.png
Polyhedron chamfered 6 pyritohedral.png
Pyritohedron and its axis truncation
Modelle, Kristallform Wurfel-Pentagondodekaeder -Krantz 379, 380- (4).jpg
Modelle, Kristallform Wurfel-Pentagondodekaeder -Krantz 379, 380- (2).jpg
Historical crystallographic models of axis truncation and axis light truncation of pyritohedron
The truncated octahedron looks similar; but its hexagons correspond to the 8 faces, not to the 12 edges, of the octahedron, i.e. to the 8 vertices, not to the 12 edges, of the cube. Polyhedron truncated 8 max.png
The truncated octahedron looks similar; but its hexagons correspond to the 8 faces, not to the 12 edges, of the octahedron, i.e. to the 8 vertices, not to the 12 edges, of the cube.
Octahedral chamfers and their duals
Polyhedron chamfered 6.png
chamfered cube (canonical form)
Polyhedron 6-8 dual.png
rhombic dodecahedron
Polyhedron chamfered 8.png
chamfered octahedron (canonical form)
Polyhedron chamfered 6 dual.png
tetrakis cuboctahedron
Polyhedron 6-8.png
cuboctahedron
Polyhedron chamfered 8 dual.png
triakis cuboctahedron

Chamfered octahedron

Chamfered octahedron
Polyhedron chamfered 8 edeq max.png
(equilateral-faced form)
Conway notation cO = t3daO
Faces8 congruent equilateral triangles
12 congruent hexagons (equilateral for a certain chamfering depth)
Edges48 (2 types:
triangle-hexagon,
hexagon-hexagon)
Vertices30 (2 types)
Vertex configuration (24) 3.6.6
(6) 6.6.6.6
Symmetry Oh, [4,3], (*432)
Dual polyhedron Triakis cuboctahedron
Properties convex, equilateral (for a certain chamfering depth)

In geometry, the chamfered octahedron (or tritruncated rhombic dodecahedron) is a convex polyhedron constructed by truncating the 8 order-3 vertices of the rhombic dodecahedron. These truncated vertices become congruent equilateral triangles, and the original 12 rhombic faces become congruent flattened hexagons.
For a certain depth of truncation, all final edges have same length; then, the hexagons are equilateral, but not regular).

Historical drawings of rhombic dodecahedron and slightly chamfered octahedron Brockhaus and Efron Encyclopedic Dictionary b48 862-4.jpg
Historical drawings of rhombic dodecahedron and slightly chamfered octahedron
Modell, Kristallform Wurfel-Deltoidikositetraeder -Krantz 426-.jpg
Modell, Kristallform Oktaeder-Rhombendodekaeder -Krantz 432-.jpg
Historical models of triakis cuboctahedron and slightly chamfered octahedron

Chamfered dodecahedron

Chamfered dodecahedron
Polyhedron chamfered 12 edeq max.png
(with equal edge length)
Conway notation cD = t5daD = dk5aD
Goldberg polyhedron GV(2,0) = {5+,3}2,0
Fullerene C80 [2]
Faces12 pentagons
30 hexagons
Edges120 (2 types)
Vertices80 (2 types)
Vertex configuration (60) 5.6.6
(20) 6.6.6
Symmetry group Icosahedral (Ih)
Dual polyhedron Pentakis icosidodecahedron
Properties convex, equilateral-faced

The chamfered dodecahedron is a convex polyhedron with 80 vertices, 120 edges, and 42 faces: 30 hexagons and 12 pentagons. It is constructed as a chamfer of a regular dodecahedron. The pentagons are reduced in size and new hexagonal faces are added in place of all the original edges. Its dual is the pentakis icosidodecahedron.

It is also inaccurately called a truncated rhombic triacontahedron, although that name rather suggests a rhombicosidodecahedron. It can more accurately be called a pentatruncated rhombic triacontahedron because only the order-5 vertices are truncated.

The truncated icosahedron looks similar, but its hexagons correspond to the 20 vertices of the dodecahedron, rather than to its 30 edges. Polyhedron truncated 20 max.png
The truncated icosahedron looks similar, but its hexagons correspond to the 20 vertices of the dodecahedron, rather than to its 30 edges.
Icosahedral chamfers and their duals
Polyhedron chamfered 12.png
chamfered dodecahedron (canonical)
Polyhedron 12-20 dual.png
rhombic triacontahedron
Polyhedron chamfered 20.png
chamfered icosahedron (canonical)
Polyhedron chamfered 12 dual.png
pentakis icosidodecahedron
Polyhedron 12-20.png
icosidodecahedron
Polyhedron chamfered 20 dual.png
triakis icosidodecahedron

Chamfered icosahedron

Chamfered icosahedron
Polyhedron chamfered 20 edeq max.png
(with equal edge length)
Conway notation cI = t3daI
Faces20 triangles
30 hexagons
Edges120 (2 types)
Vertices72 (2 types)
Vertex configuration (24) 3.6.6
(12) 6.6.6.6.6
Symmetry Ih, [5,3], (*532)
Dual polyhedron Triakis icosidodecahedron
Properties convex

In geometry, the chamfered icosahedron is a convex polyhedron constructed from the rhombic triacontahedron by truncating the 20 order-3 vertices. The hexagonal faces can be made equilateral but not regular.

It can also be called a tritruncated rhombic triacontahedron, a truncation of the order-3 vertices of the rhombic triacontahedron.


Chamfered regular tilings

Chamfered regular and quasiregular tilings
Uniform tiling 44-t0.svg
Square tiling, Q
{4,4}
Uniform tiling 63-t2.svg
Triangular tiling, Δ
{3,6}
Uniform tiling 63-t0.svg
Hexagonal tiling, H
{6,3}
1-uniform 7 dual.svg
Rhombille, daH
dr{6,3}
Chamfer square tiling.svg Chamfer triangular tiling.svg Chamfer hexagonal tiling.svg Chamfered rhombille tiling.svg
cQ cH cdaH

Relation to Goldberg polyhedra

The chamfer operation applied in series creates progressively larger polyhedra with new hexagonal faces replacing edges from the previous one. The chamfer operator transforms GP(m,n) to GP(2m,2n).

A regular polyhedron, GP(1,0), create a Goldberg polyhedra sequence: GP(1,0), GP(2,0), GP(4,0), GP(8,0), GP(16,0)...

GP(1,0)GP(2,0)GP(4,0)GP(8,0)GP(16,0)...
GPIV
{4+,3}
Uniform polyhedron-43-t0.svg
C
Truncated rhombic dodecahedron2.png
cC
Octahedral goldberg polyhedron 04 00.svg
ccC
Octahedral goldberg polyhedron 08 00.svg
cccC
GPV
{5+,3}
Uniform polyhedron-53-t0.svg
D
Truncated rhombic triacontahedron.png
cD
Chamfered chamfered dodecahedron.png
ccD
Chamfered chamfered chamfered dodecahedron.png
cccD
Chamfered chamfered chamfered chamfered dodecahedron.png
ccccD
GPVI
{6+,3}
Uniform tiling 63-t0.svg
H
Truncated rhombille tiling.png
cH
Chamfered chamfered hexagonal tiling.png
ccH

cccH

ccccH

The truncated octahedron or truncated icosahedron, GP(1,1) creates a Goldberg sequence: GP(1,1), GP(2,2), GP(4,4), GP(8,8)...

GP(1,1)GP(2,2)GP(4,4)...
GPIV
{4+,3}
Uniform polyhedron-43-t12.svg
tO
Chamfered truncated octahedron.png
ctO
Chamfered chamfered truncated octahedron.png
cctO
GPV
{5+,3}
Uniform polyhedron-53-t12.svg
tI
Chamfered truncated icosahedron.png
ctI
Chamfered chamfered truncated icosahedron.png
cctI
GPVI
{6+,3}
Uniform tiling 63-t12.svg
tH
Chamfered truncated triangular tiling.png
ctH

cctH

A truncated tetrakis hexahedron or pentakis dodecahedron, GP(3,0), creates a Goldberg sequence: GP(3,0), GP(6,0), GP(12,0)...

GP(3,0)GP(6,0)GP(12,0)...
GPIV
{4+,3}
Octahedral goldberg polyhedron 03 00.svg
tkC
Octahedral goldberg polyhedron 06 00.svg
ctkC
cctkC
GPV
{5+,3}
Conway polyhedron Dk6k5tI.png
tkD
Chamfered truncated pentakis dodecahedron.png
ctkD
cctkD
GPVI
{6+,3}
Truncated hexakis hexagonal tiling.png
tkH
Chamfered truncated hexakis hexagonal tiling.png
ctkH
cctkH

Chamfered polytopes and honeycombs

Like the expansion operation, chamfer can be applied to any dimension. For polygons, it triples the number of vertices. For polychora, new cells are created around the original edges. The cells are prisms, containing two copies of the original face, with pyramids augmented onto the prism sides.

See also

Related Research Articles

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A cuboctahedron is a polyhedron with 8 triangular faces and 6 square faces. A cuboctahedron has 12 identical vertices, with 2 triangles and 2 squares meeting at each, and 24 identical edges, each separating a triangle from a square. As such, it is a quasiregular polyhedron, i.e. an Archimedean solid that is not only vertex-transitive but also edge-transitive. It is radially equilateral.

<span class="mw-page-title-main">Cube</span> Solid object with six equal square faces

In geometry, a cube is a three-dimensional solid object bounded by six square faces, facets, or sides, with three meeting at each vertex. Viewed from a corner, it is a hexagon and its net is usually depicted as a cross.

In geometry, a dodecahedron or duodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagons as faces, which is a Platonic solid. There are also three regular star dodecahedra, which are constructed as stellations of the convex form. All of these have icosahedral symmetry, order 120.

<span class="mw-page-title-main">Rhombic dodecahedron</span> Catalan solid with 12 faces

In geometry, the rhombic dodecahedron is a convex polyhedron with 12 congruent rhombic faces. It has 24 edges, and 14 vertices of 2 types. It is a Catalan solid, and the dual polyhedron of the cuboctahedron.

<span class="mw-page-title-main">Rhombic triacontahedron</span> Catalan solid with 30 faces

The rhombic triacontahedron, sometimes simply called the triacontahedron as it is the most common thirty-faced polyhedron, is a convex polyhedron with 30 rhombic faces. It has 60 edges and 32 vertices of two types. It is a Catalan solid, and the dual polyhedron of the icosidodecahedron. It is a zonohedron.

In geometry, a zonohedron is a convex polyhedron that is centrally symmetric, every face of which is a polygon that is centrally symmetric. Any zonohedron may equivalently be described as the Minkowski sum of a set of line segments in three-dimensional space, or as a three-dimensional projection of a hypercube. Zonohedra were originally defined and studied by E. S. Fedorove, a Russian crystallographer. More generally, in any dimension, the Minkowski sum of line segments forms a polytope known as a zonotope.

<span class="mw-page-title-main">Tetrakis hexahedron</span> Catalan solid with 24 faces

In geometry, a tetrakis hexahedron is a Catalan solid. Its dual is the truncated octahedron, an Archimedean solid.

<span class="mw-page-title-main">Disdyakis triacontahedron</span> Catalan solid with 120 faces

In geometry, a disdyakis triacontahedron, hexakis icosahedron, decakis dodecahedron or kisrhombic triacontahedron is a Catalan solid with 120 faces and the dual to the Archimedean truncated icosidodecahedron. As such it is face-uniform but with irregular face polygons. It slightly resembles an inflated rhombic triacontahedron: if one replaces each face of the rhombic triacontahedron with a single vertex and four triangles in a regular fashion, one ends up with a disdyakis triacontahedron. That is, the disdyakis triacontahedron is the Kleetope of the rhombic triacontahedron. It is also the barycentric subdivision of the regular dodecahedron and icosahedron. It has the most faces among the Archimedean and Catalan solids, with the snub dodecahedron, with 92 faces, in second place.

<span class="mw-page-title-main">Chamfered dodecahedron</span> Goldberg polyhedron with 42 faces

In geometry, the chamfered dodecahedron is a convex polyhedron with 80 vertices, 120 edges, and 42 faces: 30 hexagons and 12 pentagons. It is constructed as a chamfer (edge-truncation) of a regular dodecahedron. The pentagons are reduced in size and new hexagonal faces are added in place of all the original edges. Its dual is the pentakis icosidodecahedron.

<span class="mw-page-title-main">Conway polyhedron notation</span> Method of describing higher-order polyhedra

In geometry and topology, Conway polyhedron notation, invented by John Horton Conway and promoted by George W. Hart, is used to describe polyhedra based on a seed polyhedron modified by various prefix operations.

In geometry, a polytope or a tiling is isotoxal or edge-transitive if its symmetries act transitively on its edges. Informally, this means that there is only one type of edge to the object: given two edges, there is a translation, rotation, and/or reflection that will move one edge to the other while leaving the region occupied by the object unchanged.

In geometry, a quasiregular polyhedron is a uniform polyhedron that has exactly two kinds of regular faces, which alternate around each vertex. They are vertex-transitive and edge-transitive, hence a step closer to regular polyhedra than the semiregular, which are merely vertex-transitive.

<span class="mw-page-title-main">Simple polytope</span> N-dimensional polytope with vertices adjacent to N facets

In geometry, a d-dimensional simple polytope is a d-dimensional polytope each of whose vertices are adjacent to exactly d edges (also d facets). The vertex figure of a simple d-polytope is a (d – 1)-simplex.

<span class="mw-page-title-main">Pentakis icosidodecahedron</span> Geodesic polyhedron with 80 faces

In geometry, the pentakis icosidodecahedron or subdivided icosahedron is a convex polyhedron with 80 triangular faces, 120 edges, and 42 vertices. It is a dual of the truncated rhombic triacontahedron.

In geometry and polyhedral combinatorics, the Kleetope of a polyhedron or higher-dimensional convex polytope P is another polyhedron or polytope PK formed by replacing each facet of P with a shallow pyramid. Kleetopes are named after Victor Klee.

<span class="mw-page-title-main">Goldberg polyhedron</span> Convex polyhedron made from hexagons and pentagons

In mathematics, and more specifically in polyhedral combinatorics, a Goldberg polyhedron is a convex polyhedron made from hexagons and pentagons. They were first described in 1937 by Michael Goldberg (1902–1990). They are defined by three properties: each face is either a pentagon or hexagon, exactly three faces meet at each vertex, and they have rotational icosahedral symmetry. They are not necessarily mirror-symmetric; e.g. GP(5,3) and GP(3,5) are enantiomorphs of each other. A Goldberg polyhedron is a dual polyhedron of a geodesic polyhedron.

<span class="mw-page-title-main">Icosahedron</span> Polyhedron with 20 faces

In geometry, an icosahedron is a polyhedron with 20 faces. The name comes from Ancient Greek εἴκοσι (eíkosi) 'twenty', and ἕδρα (hédra) 'seat'. The plural can be either "icosahedra" or "icosahedrons".

<span class="mw-page-title-main">Geodesic polyhedron</span> Polyhedron made from triangles that approximates a sphere

A geodesic polyhedron is a convex polyhedron made from triangles. They usually have icosahedral symmetry, such that they have 6 triangles at a vertex, except 12 vertices which have 5 triangles. They are the dual of corresponding Goldberg polyhedra, of which all but the smallest one have mostly hexagonal faces.

<span class="mw-page-title-main">Order-5 truncated pentagonal hexecontahedron</span>

The order-5 truncated pentagonal hexecontahedron is a convex polyhedron with 72 faces: 60 hexagons and 12 pentagons triangular, with 210 edges, and 140 vertices. Its dual is the pentakis snub dodecahedron.

References

  1. Spencer 1911, p. 575, or p. 597 on Wikisource, CRYSTALLOGRAPHY, 1. CUBIC SYSTEM, TETRAHEDRAL CLASS, FIGS. 30 & 31.
  2. "C80 Isomers". Archived from the original on 2014-08-12. Retrieved 2014-08-09.

Sources