Uniform polyhedron

A uniform polyhedron is a polyhedron which has regular polygons as faces and is vertex-transitive (transitive on its vertices, isogonal, i.e. there is an isometry mapping any vertex onto any other). It follows that all vertices are congruent, and the polyhedron has a high degree of reflectional and rotational symmetry.

Uniform polyhedra may be regular (if also face and edge transitive), quasi-regular (if edge transitive but not face transitive) or semi-regular (if neither edge nor face transitive). The faces and vertices need not be convex, so many of the uniform polyhedra are also star polyhedra.

Excluding the infinite sets, there are 75 uniform polyhedra (or 76 if edges are allowed to coincide).

There are also two infinite sets of uniform prisms and antiprisms, including convex and star forms.

Dual polyhedra to uniform polyhedra are face-transitive (isohedral) and have regular vertex figures, and are generally classified in parallel with their dual (uniform) polyhedron. The dual of a regular polyhedron is regular, while the dual of an Archimedean solid is a Catalan solid.

Contents

History

Regular star polyhedra:

Other 53 nonregular star polyhedra:

Uniform star polyhedra

The 57 nonprismatic nonconvex forms are compiled by Wythoff constructions within Schwarz triangles.

Main article: uniform star polyhedron

Convex forms by Wythoff construction

The convex uniform polyhedra can be named by Wythoff construction operations and can be named in relation to the regular form.

In more detail the convex uniform polyhedron are given below by their Wythoff construction within each symmetry group.

Within the Wythoff construction, there are repetitions created by lower symmetry forms. The cube is a regular polyhedron, and a square prism. The octahedron is a regular polyhedron, and a triangular antiprism. The octahedron is also a rectified tetrahedron. Many polyhedra are repeated from different construction sources and are colored differently.

The Wythoff construction applies equally to uniform polyhedra and uniform tilings on the surface of a sphere, so images of both are given. The spherical tilings including the set of hosohedrons and dihedrons which are degenerate polyhedra.

These symmetry groups are formed from the reflectional point groups in three dimensions, each represented by a fundamental triangle (p q r), where p>1, q>1, r>1 and 1/p+1/q+1/r<1.

The remaining nonreflective forms are constructed by alternation operations applied to the polyhedra with an even number of sides.

Along with the prisms and their dihedral symmetry, the spherical Wythoff construction process adds two regular classes which become degenerate as polyhedra - the dihedra and hosohedra, the first having only two faces, and the second only two vertices. The truncation of the regular hosohedra creates the prisms.

Below the convex uniform polyhedra are indexed 1-18 for the nonprismatic forms as they are presented in the tables by symmetry form. Repeated forms are in brackets.

For the infinite set of prismatic forms, they are indexed in four families:

  1. Hosohedrons H2... (Only as spherical tilings)
  2. Dihedrons D2... (Only as spherical tilings)
  3. Prisms P3... (Truncated hosohedrons)
  4. Antiprisms A3... (Snub prisms)

Summary tables

Johnson name Parent Truncated Rectified Bitruncated
(tr. dual)		 Birectified
(dual)		 Cantellated Omnitruncated
(Cantitruncated)		 Snub
Extended
Schläfli symbol		 \begin{Bmatrix} p , q \end{Bmatrix} t\begin{Bmatrix} p , q \end{Bmatrix} \begin{Bmatrix} p \\ q \end{Bmatrix} t\begin{Bmatrix} q , p \end{Bmatrix} \begin{Bmatrix} q , p \end{Bmatrix} r\begin{Bmatrix} p \\ q \end{Bmatrix} t\begin{Bmatrix} p \\ q \end{Bmatrix} s\begin{Bmatrix} p \\ q \end{Bmatrix}
t0{p,q} t0,1{p,q} t1{p,q} t1,2{p,q} t2{p,q} t0,2{p,q} t0,1,2{p,q} s{p,q}
Wythoff symbol
p-q-2		 q | p 2 2 q | p 2 | p q 2 p | q p | q 2 p q | 2 p q 2 | | p q 2
Coxeter-Dynkin diagram
Vertex figure pq (q.2p.2p) (p.q.p.q) (p. 2q.2q) qp (p. 4.q.4) (4.2p.2q) (3.3.p. 3.q)
Tetrahedral
3-3-2
{3,3}
(3.6.6)
(3.3.3.3)
(3.6.6)
{3,3}
(3.4.3.4)
(4.6.6)
(3.3.3.3.3)
Octahedral
4-3-2
{4,3}
(3.8.8)
(3.4.3.4)
(4.6.6)
{3,4}
(3.4.4.4)
(4.6.8)
(3.3.3.3.4)
Icosahedral
5-3-2
{5,3}
(3.10.10)
(3.5.3.5)
(5.6.6)
{3,5}
(3.4.5.4)
(4.6.10)
(3.3.3.3.5)

And a sampling of Dihedral symmetries:

(p 2 2) Parent Truncated Rectified Bitruncated
(tr. dual)		 Birectified
(dual)		 Cantellated Omnitruncated
(Cantitruncated)		 Snub
Extended
Schläfli symbol		 \begin{Bmatrix} p , 2 \end{Bmatrix} t\begin{Bmatrix} p , 2 \end{Bmatrix} \begin{Bmatrix} p \\ 2 \end{Bmatrix} t\begin{Bmatrix} 2 , p \end{Bmatrix} \begin{Bmatrix} 2 , p \end{Bmatrix} r\begin{Bmatrix} p \\ 2 \end{Bmatrix} t\begin{Bmatrix} p \\ 2 \end{Bmatrix} s\begin{Bmatrix} p \\ 2 \end{Bmatrix}
t0{p,2} t0,1{p,2} t1{p,2} t1,2{p,2} t2{p,2} t0,2{p,2} t0,1,2{p,2} s{p,2}
Wythoff symbol 2 | p 2 2 2 | p 2 | p 2 2 p | 2 p | 2 2 p 2 | 2 p 2 2 | | p 2 2
Coxeter-Dynkin diagram
Vertex figure p2 (2.2p.2p) (p. 2.p. 2) (p. 4.4) 2p (p. 4.2.4) (4.2p.4) (3.3.p. 3.2)
Dihedral
(2 2 2)
{2,2}		 2.4.4
2.2.2.2
4.4.2
{2,2}		 2.4.2.4
4.4.4
3.3.3.2
Dihedral
(3 2 2)
{3,2}
2.6.6		 2.3.2.3
4.4.3
{2,3}		 2.4.3.4
4.4.6
3.3.3.3
Dihedral
(4 2 2)		 {4,2} 2.8.8 2.4.2.4
4.4.4
{2,4}		 2.4.4.4
4.4.8
3.3.3.4
Dihedral
(5 2 2)		 {5,2} 2.10.10 2.5.2.5
4.4.5		 {2,5} 2.4.5.4
4.4.10
3.3.3.5
Dihedral
(6 2 2)
{6,2}
2.12.12
2.6.2.6
4.4.6
{2,6}
2.4.6.4
4.4.12
3.3.3.6

Wythoff construction operators


Example forms from the cube and octahedron
Operation Extended
Schläfli
symbols		 Coxeter-
Dynkin
diagram		 Description
Parent t0{p,q} \begin{Bmatrix} p , q \end{Bmatrix} Any regular polyhedron or tiling
Rectified t1{p,q} \begin{Bmatrix} p \\ q \end{Bmatrix} The edges are fully truncated into single points. The polyhedron now has the combined faces of the parent and dual.
Birectified
Also Dual		 t2{p,q} \begin{Bmatrix} q , p \end{Bmatrix} The birectified (dual) is a further truncation so that the original faces are reduced to points. New faces are formed under each parent vertex. The number of edges is unchanged and are rotated 90 degrees. The dual of the regular polyhedron {p, q} is also a regular polyhedron {q, p}.
Truncated t0,1{p,q} t\begin{Bmatrix} p , q \end{Bmatrix} Each original vertex is cut off, with a new face filling the gap. Truncation has a degree of freedom, which has one solution that creates a uniform truncated polyhedron. The polyhedron has its original faces doubled in sides, and contains the faces of the dual.
Bitruncated t1,2{p,q} t\begin{Bmatrix} q , p \end{Bmatrix} Same as truncated dual.
Cantellated
(or rhombated)
(Also expanded)		 t0,2{p,q} r\begin{Bmatrix} p \\ q \end{Bmatrix} In addition to vertex truncation, each original edge is beveled with new rectangular faces appearing in their place. A uniform cantellation is half way between both the parent and dual forms.
Omnitruncated
(or cantitruncated)		 t0,1,2{p,q} t\begin{Bmatrix} p \\ q \end{Bmatrix} The truncation and cantellation operations are applied together to create an omnitruncated form which has the parent's faces doubled in sides, the dual's faces doubled in sides, and squares where the original edges existed.
Snub s{p,q} s\begin{Bmatrix} p \\ q \end{Bmatrix} The snub takes the omnitruncated form and rectifies alternate vertices. (This operation is only possible for polyhedra with all even-sided faces.) All the original faces end up with half as many sides, and the squares degenerate into edges. Since the omnitruncated forms have 3 faces/vertex, new triangles are formed. Usually these alternated faceting forms are slightly deformed thereafter in order to end again as uniform polyhedra. The possibility of the latter variation depends on the degree of freedom.

(3 3 2) Td Tetrahedral symmetry

The tetrahedral symmetry of the sphere generates 5 uniform polyhedra, and a 6th form by a snub operation.

The tetrahedral symmetry is represented by a fundamental triangle with one vertex with two mirrors, and two vertices withr three mirrors, represented by the symbol (3 3 2). It can also be represented by the Coxeter group A2 or [3,3], as well as a Coxeter-Dynkin diagram: .

There are 24 triangles, visible in the faces of the tetrakis hexahedron and alternately colored triangles on a sphere:

# Name Graph
A3		 Graph
A2		 Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[3]
(4)		 Pos. 1

[ ]x[ ]
(6)		 Pos. 0

[3]
(4)		 Faces Edges Vertices
1 tetrahedron
{3,3}
{3}		 4 6 4
[1] Birectified tetrahedron
(Same as tetrahedron)
t2{3,3}
{3}		 4 6 4
2 rectified tetrahedron
(Same as octahedron)
t1{3,3}
{3}
{3}		 8 12 6
3 truncated tetrahedron
t0,1{3,3}
{6}
{3}		 8 18 12
[3] Bitruncated tetrahedron
(Same as truncated tetrahedron)
t1,2{3,3}
{3}
{6}		 8 18 12
4 cantellated tetrahedron
(Same as cuboctahedron)
t0,2{3,3}
{3}
{4}
{3}		 14 24 12
5 omnitruncated tetrahedron
(Same as truncated octahedron)
t0,1,2{3,3}
{6}
{4}
{6}		 14 36 24
6 Snub tetrahedron
(Same as icosahedron)
s{3,3}
{3}
2 {3}
{3}		 20 30 12

(4 3 2) Oh Octahedral symmetry

The octahedral symmetry of the sphere generates 7 uniform polyhedra, and a 3 more by alternation. Four of these forms are repeated from the tetrahedral symmetry table above.

The octaahedral symmetry is represented by a fundamental triangle (4 3 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group B2 or [4,3], as well as a Coxeter-Dynkin diagram: .

There are 48 triangles, visible in the faces of the disdyakis dodecahedron and alternately colored triangles on a sphere:

# Name Graph
B3		 Graph
B2		 Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[4]
(8)		 Pos. 1

[ ]x[ ]
(6)		 Pos. 0

[3]
(12)		 Faces Edges Vertices
7 Cube
{4,3}
{4}		 6 12 8
[2] Octahedron
{3,4}
{3}		 8 12 6
[4] rectified cube
rectified octahedron
(Cuboctahedron)
{4,3}
{4}
{3}		 14 24 12
8 Truncated cube
t0,1{4,3}
{8}
{3}		 14 36 24
[5] Truncated octahedron
t0,1{3,4}
{4}
{6}		 14 36 24
9 Cantellated cube
cantellated octahedron
Rhombicuboctahedron
t0,2{4,3}
{8}
{4}
{6}		 26 48 24
10 Omnitruncated cube
omnitruncated octahedron
Truncated cuboctahedron
t0,1,2{4,3}
{8}
{4}
{6}		 26 72 48
[6] Alternated truncated octahedron
(Same as Icosahedron)
h0,1{3,4}
{3}
{3}		 20 30 12
[1] Alternated cube
(Same as tetrahedron)
h{4,3}
1/2 {3}		 6 12 8
11 Snub cube
s{4,3}
{4}
2 {3}
{3}		 38 60 24

(5 3 2) Ih Icosahedral symmetry

The icosahedral symmetry of the sphere generates 7 uniform polyhedra, and a 1 more by alternation. Only one is repeated from the tetrahedral and octahedral symmetry table above.

The icosahedral symmetry is represented by a fundamental triangle (5 3 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group G2 or [5,3], as well as a Coxeter-Dynkin diagram: .

There are 120 triangles, visible in the faces of the disdyakis triacontahedron and alternately colored triangles on a sphere:

# Name Graph
(A2)
[6]		 Graph
(H3)
[10]		 Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[5]
(12)		 Pos. 1

[ ]x[ ]
(30)		 Pos. 0

[3]
(20)		 Faces Edges Vertices
12 Dodecahedron
{5,3}
{5}		 12 30 20
[6] Icosahedron
{3,5}
{3}		 20 30 12
13 Rectified dodecahedron
Rectified icosahedron
Icosidodecahedron
t1{5,3}
{5}
{3}		 32 60 30
14 Truncated dodecahedron
t0,1{5,3}
{10}
{3}		 32 90 60
15 Truncated icosahedron
t0,1{3,5}
{5}
{6}		 32 90 60
16 Cantellated dodecahedron
Cantellated icosahedron
Rhombicosidodecahedron
t0,2{5,3}
{5}
{4}
{3}		 62 120 60
17 Omnitruncated dodecahedron
Omnitruncated icosahedron
Truncated icosidodecahedron
t0,1,2{5,3}
{10}
{4}
{6}		 62 180 120
18 Snub dodecahedron
Snub icosahedron
s{5,3}
{5}
2 {3}
{3}		 92 150 60

(p 2 2) Prismatic [p,2], I2(p) family (Dph Dihedral symmetry)

Main article: Prismatic uniform polyhedron

The dihedral symmetry of the sphere generates two infinite sets of uniform polyhedra, prisms and antiprisms, and two more infinite set of degenerate polygons, the hosohedrons and dihedrons which exists as tilings on the sphere.

The dihedral symmetry is represented by a fundamental triangle (p 2 2) counting the mirrors at each vertex. It can also be represented by the Coxeter group I2(p) or [n,2], as well as a prismatic Coxeter-Dynkin diagram: .

Below are the first five dihedral symmetries: D2 ... D6. The dihedral symmetry Dp has order 4n, represented the faces of a bipyramid, and on the sphere as an equator line on the longitude, and n equally-spaced lines of longitude.

(2 2 2) dihedral symmetry

There are 8 fundamental triangles, visible in the faces of the square bipyramid (Octahedron) and alternately colored triangles on a sphere:

# Name Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[2]
(2)		 Pos. 1

[ ]x[ ]
(2)		 Pos. 0

[ ]x[ ]
(2)		 Faces Edges Vertices
D2
H2		 digonal dihedron
digonal hosohedron
{2,2}
{2}		 2 2 2
D4 truncated digonal dihedron
(Same as square dihedron)
t{2,2}={4,2}
{4}		 2 4 4
P4
[7]		 omnitruncated digonal dihedron
(Same as cube)
t0,1,2{2,2}
{4}
{4}
{4}		 6 12 8
A2
[1]		 snub digonal dihedron
(Same as tetrahedron)
s{2,2}
{3}		   4 6 4

(3 2 2) D3hdihedral symmetry

There are 12 fundamental triangles, visible in the faces of the hexagonal bipyramid and alternately colored triangles on a sphere:

# Name Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[3]
(2)		 Pos. 1

[ ]x[ ]
(3)		 Pos. 0

[ ]x[ ]
(3)		 Faces Edges Vertices
D3 Trigonal dihedron
{3,2}
{3}		 2 3 3
H3 Trigonal hosohedron
{2,3}
{2}		 3 3 2
D6 Truncated trigonal dihedron
(Same as hexagonal dihedron)
t{3,2}
{6}		 2 6 6
P3 Truncated trigonal hosohedron
(Triangular prism)
t{2,3}
{3}
{4}		 5 9 6
P6 Omnitruncated trigonal dihedron
(Hexagonal prism)
t{2,3}
{6}
{4}
{4}		 8 18 12
A3
[2]		 Snub trigonal dihedron
(Same as Triangular antiprism)
(Same as octahedron)
s{2,3}
{3}
{3}		   8 12 6

(4 2 2) D4hdihedral symmetry

There are 16 fundamental triangles, visible in the faces of the octagonal bipyramid and alternately colored triangles on a sphere:

# Name Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[4]
(2)		 Pos. 1

[ ]x[ ]
(4)		 Pos. 0

[ ]x[ ]
(4)		 Faces Edges Vertices
D4 square dihedron
{4,2}
{4}		 2 4 4
H4 square hosohedron
{2,4}
{2}		 4 4 2
D8 Truncated square dihedron
(Same as octagonal dihedron)
t{4,2}
{8}		 2 8 8
P4
[7]		 Truncated square hosohedron
(Cube)
t{2,4}
{4}
{4}		 6 12 8
D8 Omnitruncated square dihedron
(Octagonal prism)
t{2,4}
{8}
{4}
{4}		 10 24 16
A4 Snub square dihedron
(Square antiprism)
t{2,4}
{4}
{3}		   10 16 8

(5 2 2) D5h dihedral symmetry

There are 20 fundamental triangles, visible in the faces of the decagonal bipyramid and alternately colored triangles on a sphere:

# Name Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[5]
(2)		 Pos. 1

[ ]x[ ]
(5)		 Pos. 0

[ ]x[ ]
(5)		 Faces Edges Vertices
D5 Pentagonal dihedron
{5,2}
{5}		 2 5 5
H5 Pentagonal hosohedron
{2,5}
{2}		 5 5 2
D10 Truncated pentagonal dihedron
(Same as decagonal dihedron)
t{5,2}
{10}		 2 10 10
P5 Truncated pentagonal hosohedron
(Same as pentagonal prism)
t{2,5}
{5}
{4}		 7 15 10
P10 Omnitruncated pentagonal dihedron
(Decagonal prism)
t{2,5}
{10}
{4}
{4}		 12 30 20
A5 Snub pentagonal dihedron
(Pentagonal antiprism)
t{2,5}
{5}
{3}		   12 20 10

(6 2 2) D6hdihedral symmetry

There are 24 fundamental triangles, visible in the faces of the dodecagonal bipyramid and alternately colored triangles on a sphere.

# Name Picture Tiling Vertex
figure		 Coxeter-Dynkin
and Schläfli
symbols		 Face counts by position Element counts
Pos. 2

[6]
(2)		 Pos. 1

[ ]x[ ]
(6)		 Pos. 0

[ ]x[ ]
(6)		 Faces Edges Vertices
D6 Hexagonal dihedron
{6,2}
{6}		 2 6 6
H6 Hexagonal hosohedron
{2,6}
{2}		 6 6 2
D12 Truncated hexagonal dihedron
(Same as dodecagonal dihedron)
t{6,2}
{12}		 2 12 12
H6 Truncated hexagonal hosohedron
(Same as hexagonal prism)
t{2,6}
{6}
{4}		 8 18 12
P12 Omnitruncated hexagonal dihedron
(Dodecagonal prism)
t{2,6}
{12}
{4}
{4}		 14 36 24
A6 Snub hexagonal dihedron
(Hexagonal antiprism)
t{2,6}
{6}
{3}		   14 24 12

See also

Notes

  1. ^ Closed-Form Expressions for Uniform Polyhedra and Their Duals, Peter W. Messer, Discrete Comput Geom 27:353–375 (2002)

References

External links