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Here we present convex isohedral dice based on the methodology introduced by Mogensen [4], where we use the following notation
V: number of vertices of the die
N: number of faces of the die
E: number of edges of the die.
Such dice are characterized by identical faces where
M: number of sides (and corners) of a face (not
of the die!)
It can be shown that for isohedra 2<M<6, hence the faces must thus be triangles, quadrangles, or pentagons.
While all the faces on the dice are equivalent, the same is not true for the vertices. The different types of vertices are labeled with a number i, i=1,2,... up to the number of different vertices, with
Ri: number of corners that meet in a vertex
(rank)
Vi: number a vertex type occurs
Mi: number of different corners a vertex is made
out of
The Vertex degree used by Pegg [5] is similar to Mogensen’s Ri, and Pegg’s edge code is equivalent to Mogensen’s vertex type. If a greek letter occurs only once in an edge code, that edge is a singlet, if it occurs twice it is a doublet.
An alternative construction of Isohedra is based on isohedral transforms, as introduced by loki3 [9].
In brackets we include Mogensen’s type and loki3’s isohedral transform, e.g. for the Tetrahedron (D, 4T).
A polyhedron with faces that are all congruent equilateral triangles is called a Deltahedron. There are five deltahedra which are isohedra: regular tetrahedron, regular trigonal dipyramid, regular octahedron, regular pentagonal dipyramid, and regular icosahedron.
N=4, M=3, R=3, V=4, E=6 [3,3,3],aaa Only one type of vertex with 3 edges. Platonic solid |
Regular Trigonal Dipyramid (I) N=6, M=3, M1=2, R1=4, V1=3, M2=1, R2=3, V2=2 [4,4,3],aab 1 doublet plus 1 singlet corner. The singlet and doublet corners are part of different types of vertices. This is a special case where the triangles are equilateral. However, there are still two different vertex types (and thus this is not a Platonic solid). |
(E) N=8, M=3, R=4, V=6, E=12 [4,4,4],aaa Only one type of vertex with 4 edges. Platonic solid, dual of the cube. |
Regular Pentagonal Dipyramid (I) N=10, M=3, M1=2, R1=4, V1=5, M2=1, R2=5, V2=2 [4,4,5],aab 1 doublet plus 1 singlet corner. The singlet and doublet corners are part of different types of vertices. This is a special case where the triangles are equilateral. However, there are still two different vertex types (and thus this is not a Platonic solid). |
(F) N=20, M=3, R=5, V=12, E=30 [5,5,5],aaa Only one type of vertex with 5 edges. Platonic solid, dual of the dodecahedron |
Isosceles Tetrahedron / Tetragonal Disphenoid (D) N=4, M=3, V=4, R=3, E=6 [3,3,3],aab 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of the same type of vertex. The Iscosceles Tetrahedron has only one type of vertex, but in each vertex one singlet and two doublet corners meet, satisfying Mogensen’s equation (8). (Note: Mogensen [7] does not explicitly state that (D) need not be a regular tetrahedron) Each edge is the diagonal of a cuboid |
Triangular Dihedron / Double Pyramid / Bi-Pyramid / Di-Pyramid (I) N even (N>=6), M=3, M1=2, R1=4, V1=N/2, M2=1, R2=N/2, V2=2 [4,4,N/2],aab 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Opposing faces if N/2 even |
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Add loki3’s d6 - di-pyramid N=6 |
N=8 Tetragonal Dipyramid |
N=10 Pentagonal Dipyramid |
N=12
|
N=16 Octagonal Dipyramid |
N=36 Octadecagonal Dipyramid |
Triakis Tetrahedron / Tristetrahedron / Trigonal tristetrahedron, (J) N=12, V=8,E=18 M=3, M1=2, R1=6, V1=4, M2=1, R2=3, V2=4, [3,6,6],abb 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Triangular pyramids on tetrahedron faces, i.e., cumulation of the tetrahedron. Catalan solid, dual of the truncated tetrahedron |
Tetrakis Hexahedron / Tetrahexahedron (K) N=24, V=14, E=36 M=3, M1=2, R1=6, V1=8, M2=1, R2=4, V2=6, [4,6,6], abb 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Square pyramids on cube faces, i.e., cumulation of the cube. Catalan solid, dual of the truncated octahedron. (Note: Mogensen [7] mentions octahedron instead of cube faces) |
Triakis Octahedron / Small Triakis Octahedron/ Trisoctahedron / Trigonal Trisoctahedron (M) N=24, V=14, E=36 M=3, M1=2, R1=8, V1=6, M2=1, R2=3, V2=8, [3,8,8], abb 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Triagonal pyramids on octahedron faces, i.e., cumulation of the octahedron. Catalan solid, dual of the truncated cube. (Note: Mogensen [7] mentions cube instead of octahedron faces) |
Pentakis Dodecahedron (L) N=60, V=32, E=90 M=3, M1=2, R1=6, V1=20, M2=1,R2=5, V2=12 [5,6,6],aab 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Pentagonal pyramids on dodecahedron faces, i.e., cumulation of the dodecahedron. Catalan solid, dual of the truncated icosahedron. |
Triakis Icosahedron (N) N=60, V=32, E=90 M=3, M1=2, R1=10, V1=12, M2=1, R2=3, V2=20 [3,10,10],aab 1 doublet (a) plus 1 singlet (b) corner. The singlet and doublet corners are part of different types of vertices. Triagonal pyramids on icosahedron faces, i.e., cumulation of the icosahedron. Catalan solid , dual of the truncated dodecahedron |
Scalene tetrahedron / Rhombic disphenoid (D) N=4, M=3, R=3, V=4, E=6 [3,3,3],abg 3 singlet corners. The three singlet corners are part of the same type of vertex. The Scalene Tetrahedron has only one type of vertex, but in each vertex one each of the singlet corners meet, satisfying Mogensen’s equation (8). (Note: Mogensen [7] does not explicitly state that (D) need not be a regular tetrahedron). Each edge is the diagonal of a cuboid |
N=8, M=3, M1=2, R1=4, V1=4, M2=1, R2=4, V2=2 3 singlet corners, yet only two types of vertices. Same values as for a tetragonal Dipyramid (I), although composed of scalene triangles. This is a shape of a family called Triangular Dihedron skewed up/down (D4n) which can be constructed by skewing the equatorial vertices of a dipyramid with 4n faces up and down. "Scalenohedron" from the
Wolfram Demonstrations Project |
Skewed Triangular Dihedron / Double Pyramid / Bi-Pyramid / Di-Pyramid (O) N=8,12,16,.., M=3, M1=M2=M3=1, R1=R2=4, V1=V2=N/4, R3=N/2, V3=2 3 singlet corners, each is part of a different type of vertex. deform variant of the Dipyramid (I) This is a shape of a family called Triangular Dihedron skewed in/out (D4n) which can be constructed by squeezing the equatorial vertices of a dipyramid with 4n faces in and out from the center of the solid. "Scalenohedron" from the
Wolfram Demonstrations Project |
missing Hexakis Tetrahedron / Hextetrahedron (P) N=24, M=3, M1=1, R1=4, V1=6, M2=M3=1,R2=R3=6, V2=V3=4, V=14, E=36 [4,6,6],abg 3 singlet corners, each is part of a different type of vertice. deform variant of (K) (Note: Mogensen [7] incorrectly states that V1=4) |
Hexakis Octahedron / Disdyakis Dodecahedron / Hexoctahedron/ Octakis Hexahedron (Q) N=48, V=26, E=72 M=3, M1=1, R1=4, V1=12, M2=1, R2=6, V2=8, M3=1, R3=8, V3=6 [4,6,8],abg 3 singlet corners, each is part of a different type of vertice. Rhombic pyramids on rhombic dodecahedron faces. Catalan solid, dual of the truncated cuboctahedron |
Hexakis Icosahedron / Disdyakis Triacontahedron (R) N=120, V=62, E=180 M=3, M1=1, R1=4, V1=30, M2=1, R2=6, V2=20, M3=1, R3=10, V3=12 [4,6,10],abg 3 singlet corners, each is part of a different type of vertice. Largest non-bipolar die. Rhombic pyramids on rhombic triacontahedron faces. Catalan solid, , dual of the truncated icosidodecahedron. |
Regular Hexahedron, Cube (G) N=6, M=4, R=3, V=8, E=12 [3,3,3,3],aaaa Only one type of vertex with 3 edges. Platonic solid, dual of the octahedron. |
Rhombic Hexahedron, (S) N=6, M=4, M1=2, R1=3, V1=4, M2=2, R2=3, V2=4 [3,3,3,3], aaab 2 opposite doublet corners (a,b). Vertex type 2 consists of identical corners (b), vertex type 1 consists of different corners (a,a,b). Deform variant of the Cube (G), special case of the Trapezohedron (V)
Note that it can be proven that there are no trapezohedra made of rhombi other than for N=6 (friz). |
(T) N=12, V=14, E=24 M=4, M1=2, R1=3, V1=8, M2=2, R2=4, V2=6 [3,4,3,4],abab 2 opposite doublet corners (a,b), each is part of a different type of vertice. Catalan solid, dual of the cuboctahedron. |
(U) N=30, V=32, E=60 M=4, M1=2, R1=3, V1=20, M2=2, R2=5, V2=12 [3,5,3,5],abab 2 opposite doublet corners (a,b), each is part of a different type of vertice. Catalan solid, dual of the icosidodecahedron |
Trapezoidal Dihedron / Trapezohedron / Antidipyramids / Deltohedron Crystallographic examples: Tetragonal Trapezohedron (N=8), Hexagonal Trapezohedron (N=12) (V) N even (N>6), V=N+2, E=2N M=4, M1=3, R1=3, V1=N, M2=1, R2=N/2, V2=2 [3,3,3,N/2],aaab 1 doublet and 2 singlet corners, doublet and one of the singlets are part of the same type of vertex double cone made from kites opposing faces if N/2 odd "Streptohedron and Trapezohedron" from the Wolfram Demonstrations Project
Note that it can be proven that there is no Trigonal Trapezohedron (N=6) composed of deltoids (proof by friz). The faces have to be squares (a cube), rhombi (a rhombic cube) or irregular quadrilaterals.
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N=8 Tetragonal Trapezohedron |
N=10 Pentagonal Trapezohedron |
N=12 Hexagonal Trapezohedron |
N=14 Heptagonal Trapezohedron |
N=18 Enneagonal Trapezohedron
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N=26 Trisdecagonal Trapezohedron |
N=34 Heptadecagonal Trapezohedron |
N=50 Icosikaipentagonal Trapezohedron |
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Deltoidal Dodecahedron / Trapezoidal Dodecahedron / Trapezohedral Tristetrahedron (W) N=12, M=4, M1=2, R1=4, V1=6, M2=M3=1, R2=R3=3, V2=V3=4, V=14, E=24 [3,4,3,4],abgb 1 doublet (a) and 2 singlet (b,c) corners, doublet and both singlets all form their own vertices. deform variant of the rhombic dodecahedron (T) |
Deltoidal Icositetrahedron / Trapezoidal Icositetrahedron / Strombic Icositetrahedron / Trapezohedral Trisoctahedron / Trapezohedron, (X) N=24, V=26, E=48 M=4, M1=2, R1=4, V1=12, M2=1, R2=3, V2=8, M3=1, R3=4, V3=6 [3,4,4,4],abgb 1 doublet and 2 singlet corners, doublet and both singlets all form their own vertices. Can be made by replacing each face of a cube with four kites. Catalan solid, dual of the rhombicuboctahedron |
Deltoidal Hexecontahedron / Trapezoidal Hexecontahedron / Strombic Hexecontahedron (Y) N=60, V=62, E=120 M=4, M1=2, R1=4, V1=30, M2=1, R2=3, V2=20, M3=1, R3=5, V3=12 [3,4,5,4],abgb 1 doublet and 2 singlet corners, doublet and both singlets all form their own vertices. Can be made by replacing each face of a regular dodecahedron with five kites. Catalan solid, dual of the rhombicosidodecahedron. |
2 adjacent duplets???
Skewed Trapezoidal Dihedron / Trapezohedron / Antidipyramids / Deltohedron deform variant of the Trapezohedron (V) N even (N>=6), M=4, M1=3, R1=3, V1=N, M2=1, R2=N/2, V2=2 4 singlet corners, but only 2 types of vertices. Vertex type 2 consists of identical corners (a), vertex type 1 consists of different corners (b,c,d).
Examples: Skewed Trigonal Trapezohedron (N=6) Lengths a-d and a-b are identical.
Skewed Hexagonal Trapezohedron (N=12) Lengths a-d and a-b are identical. |
Skewed Rhombic Dodecahedron N=12, M=4, R1=4, V1=6, R2=R3=3, V2=V3=4 deform variant of (W) 4 singlet corners, but only 3 types of vertices. Vertex type 1 consists of identical corners (a), vertex type 2 consists of corners (b,b,c), vertex type 3 consists of corners (c,d,d). Length b-c and c-d are identical
??? missing in loki3’s table??? |
Dyakis Dodecahedron / Didodecahedron / Diploid N=24, M=4, M1=2, R1=4, V1=12, M2=1, R2=3, V2=8, M3=1, R3=4, V3=6, V=26, E=48 [3,4,4,4],aabg Two adjacent sides are equal. deform variant of the Deltoidal Icositetrahedron (X) |
missing Skewed Deltoidal Hexecontahedron N=60, M=4, R1=4, V1=30, R2=3, V2=20, R3=5, V3=12 deform variant of (Y) ??? missing in loki3’s table??? |
Regular (Pentagonal) Dodecahedron (H) N=12, M=5, R=3, V=20, E=30 [3,3,3,3,3],aaaaa Only one type of vertex with 3 edges. Platonic solid, dual of the icosahedron |
Octahedral Pentagonal Dodecahedron / Pentagonal Dodecahedron / (Z) N=12, M=5, M1=3, R1=3, V1=12, M2=2, R2=3, V2=8, V=20, E=30 [3,3,3,3,3],abbbb 2 doublets and 1 singlet, one doublet and the singlet are part of the same type of vertex. A deform dodecahedron which has a symmetry that mirrors the octahedron. Note that 4 edges of the pentagon are of equal length with bilateral symmetry. The vertices of Type 2 form a cube. |
include pix w/ corners Tetragonal Pentagonal Dodecahedron / Tetartoid (Æ) N=12, M=5, M1=3, R1=3, V1=12, M2=M3=1, R2=R3=3, V2=V3=4, V=20, E=30 [3,3,3,3,3],abbgg All singlet corner types, one type of vertex with three corner types, and two vertices with one corner type. Skewed dodecahedron which looks similar to the Tetrahedron.
There are no parallel faces. The design by loki3 consists of a wireframe with embedded parallel sides. |
Pentagonal Icositetrahedron / Pentagon Trioctahedron / Gyroid (Ø) N=24, M=5, M1=3, R1=3, V1=24, M2=1, R2=3, V2=8, M3=1, R3=4, V3=6, V=38, E=60 [3,3,3,3,4],abbgg Two pairs of equal adjacent sides All singlet corner types, one type of vertex with three corner types, and two vertices with one corner type. Can be made by placing sets of four pentagons on each face of a cube, turned a bit to make the corners interlace. No parallel faces. Catalan solid, dual of the snub cube Both enantiomorphous forms, known as laevo (left) and dextro (right) have the same edge code since they are mirror since they are mirror image versions of each other (thanks to loki3 for the hint) |
Pentagonal Hexecontahedron (Å) N=60, M=5, M1=3, R1=3, V1=60, M2=1, R2=3, V=20, M3=1, R3=5, V3=12, V=92, E=150 [3,3,3,3,5],abbgg All singlet corner types, one type of vertex with three corner types, and two vertices with one corner type. Can be made by placing sets of five pentagons on each face of a dodecahedron, turned a bit to make the corners interlace. No parallel faces. Catalan solid, , dual of the snub dodecahedron. Both enantiomorphous forms, known as laevo (left) and dextro (right) have the same edge code since they are mirror image versions of each other (thanks to loki3 for the hint) |
[1] Huge collection of
shapes, including some paper models and prototypes not commercially available: http://www.dicecollector.com/diceinfo_how_many_shapes.html
[2] 3D pictures of
isohera: http://mathworld.wolfram.com/Isohedron.html
[3] Wikipedia http://wikipedia.org/
[4] Mathematical
derivation of all fair dice: http://web.archive.org/web/20080501074022/http://hjem.get2net.dk/Klaudius/Dice.htm
(was: http://hjem.get2net.dk/Klaudius/Dice.htm
). Click here for a local copy in PDF
format.
[5] Another
mathematical derivation of all fair dice: http://dicephysics.info/thesis7.doc.
Click here for a local
copy in PDF format.
[6] Detailed description
of all fair dice: http://www.mathpuzzle.com/Fairdice.htm
[7] International Bone
Rollers’ Guild, Mitchel D Klink http://web.archive.org/web/20071118155413/http://members.aol.com/dicetalk/
(was http://members.aol.com/dicetalk/polymore.htm
)
[8] Polygon Names: http://www.math.com/tables/geometry/polygons.htm
[9] Isohedra (loki3): http://loki3.com/poly/isohedra.html
[10] Crystallographic Polyhedra,
Steffen Weber http://jcrystal.com/steffenweber/
Add loki3’s type code.
Pix & corner codes of cube, regular octahedron, regular D10 dipyramid, regular dodecahedron, regular icosahedron, scalene tetrahedron, Pyritohedron, Tetartoid, Pentagonal Icositetrahedron, Pentagonal Hexecontahedron
Trapezoid with 2 adjacent duplets???
Check Skewed Rhombic Dodecahedron & Skewed Deltoidal Hexecontahedron
My wish list:
Composed of isosceles triangles:
D6 Trigonal Dipyramid with isosceles triangles
Composed of scalene triangles:
D24 Hexakis Tetrahedron: no parallel faces à numbering???
Composed of irregular quadrilateral:
D12 Skewed Rhombic Dodecahedron ???
D60 Skewed Deltoidal Hexecontahedron ???
Check:
Pyritohedron M1=4?