Conway polyhedron notation

This example chart shows how 11 new forms can be derived from the cube using 3 operations. The new polyhedra are shown as maps on the surface of the cube so the topological changes are more apparent. Vertices are marked in all forms with circles.
This chart adds 3 more operations: George Hart's p=propellor operator that adds quadrilaterals, g=gyro operation that creates pentagons, and a c=Chamfer operation that replaces edges with hexagons

In geometry, 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.

Conway and Hart extended the idea of using operators, like truncation defined by Kepler, to build related polyhedra of the same symmetry. The basic descriptive operators can generate all the Archimedean solids and Catalan solids from regular seeds. For example tC represents a truncated cube, and taC, parsed as t(aC), is a truncated cuboctahedron. The simplest operator dual swaps vertex and face elements, like a dual cube is an octahedron: dC=O. Applied in a series, these operators allow many higher order polyhedra to be generated. A resulting polyhedron will have a fixed topology (vertices, edges, faces), while exact geometry is not constrained.

The seed polyhedra are the Platonic solids, represented by the first letter of their name (T,O,C,I,D); the prisms (Pn) for n-gonal forms, antiprisms (An), cupolae (Un), anticupolae (Vn) and pyramids (Yn). Any polyhedron can serve as a seed, as long as the operations can be executed on it. For example regular-faced Johnson solids can be referenced as Jn, for n=1..92.

In general, it is difficult to predict the resulting appearance of the composite of two or more operations from a given seed polyhedron. For instance ambo applied twice becomes the same as the expand operation: aa=e, while a truncation after ambo produces bevel: ta=b. There has been no general theory describing what polyhedra can be generated in by any set of operators. Instead all results have been discovered empirically.

Operations on polyhedra

Elements are given from the seed (v,e,f) to the new forms, assuming seed is a convex polyhedron: (a topological sphere, Euler characteristic = 2) An example image is given for each operation, based on a cubic seed. The basic operations are sufficient to generate the reflective uniform polyhedra and theirs duals. Some basic operations can be made as composites of others.

Special forms

The kis operator has a variation, kn, which only adds pyramids to n-sided faces.
The truncate operator has a variation, tn, which only truncates order-n vertices.

The operators are applied like functions from right to left. For example, a cuboctahedron is an ambo cube, i.e. t(C) = aC, and a truncated cuboctahedron is t(a(C)) = t(aC) = taC.

Chirality operator

The operations are visualized here on cube seed examples, drawn on the surface of the cube, with blue faces that cross original edges, and pink faces that center at original vertices.

Basic operations
OperatorExampleNameAlternate
construction
verticesedgesfacesDescription
Seed vef Seed form
rreflect vef Mirror image for chiral forms
d dual fevdual of the seed polyhedron - each vertex creates a new face
aambo dj
djd
e2ef+vNew vertices are added mid-edges, while old vertices are removed. (rectify)
This creates valence 4 vertices.
jjoin da
dad
v+f2eeThe seed is augmented with pyramids at a height high enough so that 2 coplanar triangles from 2 different pyramids share an edge.
This creates quadrilateral faces.
k
kn
kis nd = dz
dtd
v+f3e2eraises a pyramid on each face.
Akisation. Also called cumulation,[1] accretion, or pyramid-augmentation.
t
tn
truncate nd = dz
dkd
2e3ev+ftruncate all vertices.
conjugate kis
n needle kd = dt
dzd
v+f3e2eDual of truncation, triangulate with 2 triangles across every edge. This bisect faces across all vertices and edges, while removing original edges.
This transforms geodesic polyhedron (a,b) into (a+2b,a-b), for a>b.
It transforms (a,0) into (a,a), and (a,a) into '(3a,0), and (2,1) into (4,1), etc.
z zip dk = td
dnd
2e3ev+fDual of kis or truncation of the dual. This create new edges perpendicular to original edges, a truncation beyond "ambo" with new edges "zipped" between original faces. It is also called bitruncation.
This transforms Goldberg polyhedron G(a,b) into G(a+2b,a-b), for a>b.
It transforms Goldberg G(a,0) into G(a,a), and G(a,a) into G(3a,0), and G(2,1) into G(4,1), etc.
eexpand aa
dod = do
2e4ev+e+fEach vertex creates a new face and each edge creates a new quadrilateral. (cantellate)
oortho daa
ded = de
v+e+f4e2eEach n-gon faces are divided into n quadrilaterals.
g
rg=g
gyro dsd = dsv+2e+f5e2eEach n-gon face is divided into n pentagons.
s
rs=s
snub dgd = dg2e5ev+2e+f"expand and twist" – each vertex creates a new face and each edge creates two new triangles
bbevel dkda = ta
dmd = dm
4e6ev+e+fNew faces are added in place of edges and vertices. (cantitruncation)
mmeta
medial
kda = kj
dbd = db
v+e+f6e4e Triangulate with added vertices on edge and face centers.

Generating regular seeds

All of the five regular polyhedra can be generated from prismatic generators with zero to two operators:

The regular Euclidean tilings can also be used as seeds:

Examples

The cube can generate all the convex uniform polyhedra with octahedral symmetry. The first row generates the Archimedean solids and the second row the Catalan solids, the second row forms being duals of the first. Comparing each new polyhedron with the cube, each operation can be visually understood.

Cube
"seed"
ambotruncatezipexpandbevelsnub

C
dO

aC
aO

tC
zO

zC = dkC
tO

aaC = eC
eO

bC = taC
taO

sC
sO
dualjoinneedlekisorthomedialgyro

dC
O

jC
jO

dtC = kdC
kO

kC
dtO

oC
oO

dtaC = mC
mO

gC
gO

The truncated icosahedron, tI or zD, which is Goldberg polyhedron G(2,0), creates more polyhedra which are neither vertex nor face-transitive.

Truncated icosahedron seed
"seed"ambotruncatezipexpandbevelsnub

zD
tI

azI
atI

tzD
ttI

tdzD
tdtI

aazD = ezD
aatI = etI

bzD
btI

szD
stI
dualjoinneedlekisorthomedialgyro

dzD
dtI

jzD
jtI

kdzD
kdtI

kzD
ktI

ozD
otI

mzD
mtI

gzD
gtI

Geometric coordinates of derived forms

In general the seed polyhedron can be considered a tiling of a surface since the operators represent topological operations so the exact geometric positions of the vertices of the derived forms are not defined in general. A convex regular polyhedron seed can be considered a tiling on a sphere, and so the derived polyhedron can equally be assumed to be positioned on the surface of a sphere. Similar a regular tiling on a plane, such as a hexagonal tiling can be a seed tiling for derived tilings. Nonconvex polyhedra can become seeds if a related topological surface is defined to constrain the positions of the vertices. For example, toroidal polyhedra can derive other polyhedra with point on the same torus surface.

Example: A dodecahedron seed as a spherical tiling

D

tD

aD

zD = dkD

eD

bD = taD

sD

dD

nD = dtD

jD = daD

kD = dtdD

oD = deD

mD = dtaD

gD
Example: A Euclidean hexagonal tiling seed (H)

H

tH

aH

tdH = H

eH

bH = taH

sH

dH

nH = dtH

jH = daH

dtdH = kH

oH = deH

mH = dtaH

gH = dsH

Derived operations

Mixing two or more basic operations leads to a wide variety of forms. There are many more derived operations, for example, mixing two ambo, kis, or expand, along with up to 3 interspaced duals. Using alternative operators like join, truncate, ortho, bevel and medial can simply the names and remove the dual operators. The numbers of total edges of a derived operation can be computed as the product of the number of total edges of each individual operator.

Operator(s) d a
j
k, t
n, z
e
o
g
s
a&k a&e k&k k&e
k&a2
e&e
edge-multiplier 1 2 3 4 5 6 8 9 1216
Unique derived operators 8 2 8 10 2

The operations are visualized here on cube seed examples, drawn on the surface of the cube, with blue faces that cross original edges, and pink faces that cross original vertices.

Derived operations
OperatorExampleNameAlternate
construction
verticesedgesfacesDescription
Seed vef Seed form
at akd
3e 6e v+2e+f ambo of truncate
jk dak v+2e+f 6e 3e join of kis. Similar to ortho except new quad faces are inserted in place of the original edges
ak dajd 3e 6e v+2e+f ambo of kis. Similar to expand, except new vertices are added on the original edges, forming two triangles.
jt dakd = dat v+2e+f 6e 3e join of truncate. dual of ambo of truncate
tj dka 4e 6e v+e+f truncate join
ka v+e+f 6e 4e kis ambo
ea or ae aaa 4e 8e v+3e+f expanded ambo, triple ambo
oa or je daaa = jjj v+3e+f 8e 4e ortho of ambo, triple join
x=kt exalt kdkd
dtkd
v+e+f 9e 7e kis truncate, triangulate, dividing edges into 3, and adding new vertices in the center of original faces.
It transforms geodesic polyhedron (a,b) into (3a,3b).
y=tk yank dkdk
dktd
v+e+f 9e 7e truncate kis, expand with hexagons around each edge
It transforms Goldberg polyhedron G(a,b) into G(3a,3b).
nk kdk = dtk = ktd 7e 9e v+e+f needled kis
tn dkdkd = dkt = tkd 7e 9e v+e+f truncate needle
tt dkkd 7e 9e v+e+f double-truncate
kk dttd v+2e+f 9e 6e double-kis
nt kkd = dtt v+e+f 9e 7e needle truncate
tz dkk = ttd 6e 9e v+2e+f truncate zip
ke kaa v+3e+f12e8e Kis expand
to dkaa 8e12ev+3e+f truncate ortho
ek aak 6e12ev+5e+f expand kis
ok daak = dek v+5e+f12e6e ortho kis
et aadkd 6e12ev+5e+f expanded truncate
ot daadkd = det v+5e+f12e6e ortho truncate
te or ba dkdaa 8e12ev+3e+f truncate expand
ko or ma kdaa = dte
ma = mj
v+3e+f12e8e kis ortho
ab or am aka = ata 6e 12e v+5e+f ambo bevel
jb or jm daka = data v+5e+f 12e 6e joined bevel
ee aaaa v+7e+f16e8e double-expand
oo daaaa = dee 8e16ev+7e+f double-ortho

Chiral derived operations

There are more derived operators mixing at least one gyro with ambo, kis or expand, and up to 3 duals.

Operator(s) d a k e g a&gk&ge&gg&g
edge-multiplier 1 2 3 4 5 10152025
Unique derived operators 4 8 4 2
Chiral derived operations
OperatorExampleNameConstructionverticesedgesfacesDescription
Seed vef seed form
ag as
djsd = djs
v+4e+f10e5eambo gyro
jg dag = js
dasd = das
5e10ev+4e+fjoined gyro
ga gj
dsjd = dsj
v+5e+f10e4egyro ambo
sa dga = sj
dgjd = dgj
4e10ev+5e+fsnub ambo
kg dtsd = dts v+4e+f15e10ekis gyro
ts dkgd = dkg 10e15ev+4e+ftruncated snub
gk dstd v+8e+f15e6egyro kis
st dgkd 6e15ev+8e+fsnub truncation
sk dgtd v+8e+f15e6esnub kis
gt dskd 6e15ev+8e+fgyro truncation
ks kdg
dtgd = dtg
v+4e+f15e10ekis snub
tg dkdg
dksd
10e15ev+4e+ftruncated gyro
eg es
aag
v+9e+f20e10eexpanded gyro
og os
daagd = daag
10e20ev+9e+fexpanded snub
ge go
gaa
v+11e+f20e8egyro expand
se so
dgaad = dgaa
8e20ev+11e+fsnub expand
gg gs
dssd = dss
v+14e+f25e10edouble-gyro
ss sg
dggd = dgg
10e25ev+14e+fdouble-snub

Extended operators

These extended operators can't be created in general from the basic operations above. Some can be created in special cases with k and t operators only applied to specific sided faces and vertices. For example, a chamfered cube, cC, can be constructed as t4daC, as a rhombic dodecahedron, daC or jC, with its valence-4 vertices truncated. A lofted cube, lC is the same as t4kC. And a quinto-dodecahedron, qD can be constructed as t5daaD or t5deD or t5oD, a deltoidal hexecontahedron, deD or oD, with its valence-5 vertices truncated.

Some further extended operators suggest a sequence and are given a following integer for higher order forms. For example, ortho divides a square face into 4 squares, and a o3 can divide into 9 squares. o3 is a unique construction while o4 can be derived as oo, ortho applied twice. The loft operator can include an index, similar to kis, to limit the effect to faces with that number of sides.

The chamfer operation creates Goldberg polyhedra G(2,0), with new hexagons between original faces. Sequential chamfers create G(2n,0).

Extended operations
OperatorExampleNameAlternate
construction
verticesedgesfacesDescription
Seed vefSeed form
cchamfer dud v + 2e 4ef + eAn edge-truncation.
New hexagonal faces are added in place of edges. Goldberg (0,2)
- - dc f + e4ev + 2e Dual of chamfer
u subdivide dcd v+e 4ef+2e Ambo while retaining original vertices
Similar to Loop subdivision surface for triangle faces
- cd f+2e 4ev+e dual to subdivision
l
ln
loft v+2e 5ef+2eAn augmentation of each face by prism, adding a smaller copy of each face with trapezoids between the inner and outer ones.
dl
dln
f+2e 5ev+2eDual to loft
ld
lnd
f+2e 5ev+2eloft of dual
dld
dlnd
v+2e 5ef+2eConjugate to loft
dL0 f+3e6ev+2eDual to joined-lace
L0df+2e6ev+3eJoined-lace of dual
dL0dv+3e6ef+2eConjugate joined-lace
q quinto v+3e 6e f+2e ortho followed by truncation of vertices centered on original faces.
This create 2 new pentagons for every original edge.
- dq f+2e 6e v+3e dual of quinto
qd v+2e 6e f+3e quinto of dual
- dqd f+3e 6e v+2e conjugate of quinto
L0joined-lace v+2e6ef+3eSimilar to lace, except new with quad faces across original edges
L
Ln
Lace v+2e7ef+4eAn augmentation of each face by an antiprism, adding a twist smaller copy of each face, and triangles between.
An index can be added to limit the operation to faces of that many sides.
dL
dLn
f+4e7ev+2eDual of laced
Ld
Ldn
f+2e7ev+4eLace of dual
dLd
dLnd
v+4e7ef+2eDual of lace of dual
K
Kn
staKe v+2e+f 7e 4e Subdivide faces with central quads, and triangles.
An index can be added to limit the operation to faces of that many sides.
dK
dKn
4e 7e v+2e+f Dual of stake
Kd v+2e+f 7e 4e Stake of dual
dKd 4e 7e v+2e+f Conjugate of stake
M3 edge-medial-3 v+2e+f 7e 4e Similar to m3 except no diagonal edges added, creating quad faces there
dM3 4e 7e v+2e+f dual of edge-medial-3
M3d v+2e+f 7e 4e edge-medial-3 of dual
dM3d 4e 7e v+2e+f Conjugate of edge-medial-3
M0 joined-medial v+2e+f 8e 5e Like medial, but new rhombic faces in place of original edges.
dM0 v+2e+f 8e 5e dual of joined-medial
M0d v+2e+f 8e 5e joined-medial of dual
dM0d 5e 8e v+2e+f Conjugate of joined-medial
m3 medial-3 v+2e+f 9e 7e triangulate with 2 vertices added on edge and face centers.
b3 bevel-3 dm3 7e 9e v+2e+f dual to medial-3
m3d 7e 9e v+2e+f medial-3 of dual
dm3d v+2e+f 9e 7e conjugate of medial-3
o3 ortho-3 de3v+4e 9e f+4e ortho operator with 3 edge divisions
e3 expand-3 do3 f+4e 9e v+4e expand operator with 3 edge divisions
X cross v+f+3e 10e 6e Combination of kis and subdivide operation. Original edges are divided in half, with triangle and quad faces.
dX 6e 10e v+f+3e Dual to cross
Xd 6e 10e v+f+3e Cross of dual
dXd v+f+3e 10e 6e Conjugate of cross
m4 medial-4 v+3e+f 12e 8e triangulate with 3 vertices added on edge and face centers.
u5 subdivide-5 v+8e 25e f+16e Subdivide edges into 5th
This operator divides edges and faces so there are 6 triangles around each new vertex.

Extended chiral operators

These operators can't be created in general from the basic operations above. Geometric artist George W. Hart created an operation he called a propellor.

Chiral extended operations
OperatorExampleNameAlternate
construction
verticesedgesfacesDescription
"Seed" vefSeed form
p
rp=p
propellor v + 2e5ef + 2eA gyro followed by an ambo of vertices centered at original faces
- - dp = pdf + 2e5ev + 2e Same vertices as gyro, except new faces at original vertices
- 4e7ev+2e+f Like snub, except pentagons are around original faces rather than triangles
- - - v+2e+f7e4e
w=w2=w2,1
rw=w
whirl v+4e 7ef+2e gyro followed by truncation of vertices centered at original faces.
This create 2 new hexagons for every original edge, Goldberg (2,1)
The derived operator wrw transforms G(a,b) into G(7a,7b).
v
rv=v
volute dwd f+2e7ev+4e dual of whirl, a snub followed by kis on original faces.
The derived operator vrv transforms geodesic (a,b) into (7a,7b).
g3
rg3=g3
gyro-3 v+6e 11e f+4e Gyro operation create 3 pentagons along each original edge
s3
rs3=s3
snub-3 dg3d = dg3 f+4e 11e v+6e Dual of gyro-3, snub operation which divides edges into 4 middle triangles with triangles at the original vertices
w3,1
rw3,1=w3,1
whirl-3,1 v+8e 13ef+4e create 4 new hexagons for every original edge, Goldberg (3,1)
w3=w3,2
rw3=w3
whirl-3,2 v+12e 19ef+6e create 12 new hexagons for every original edge, Goldberg (3,2)

Operations that preserve original edges

These augmentation operations retain original edges, and allowing the operator to apply to any independent subset of faces. Conway notation supports an optional index to these operators to specific how many sides affected faces will have.

Operatorkiscupacuploftlacestakekis-kis
ExamplekCUCVClCLCKCkkC
Edges3e4e-f45e-f45e6e7e9e
Image
on cube
Augmentation PyramidCupolaAnticupola PrismAntiprism

Coxeter operators

Coxeter operators are sometimes useful to mix with Conway operators. For clarity in Conway notation these operations are given uppercase symbolic letter. Coxeter's t-notation defines active rings as indices a Coxeter-Dynkin diagram. So here a capital T with indices 0,1,2 define the uniform operators from a regular seed. The zero index cab ne see to represent vertices, 1 represents edges, and 2 represents faces. With T = T0,1 is an ordinary truncation, and R = T1 is a full truncation, or Rectify, the same as Conway's ambo operator. For example, r{4,3} or t1{4,3} is Coxeter's name for a cuboctahedron, a rectified cube is RC, the same as Conway's ambo cube, aC.

Coxeter extended operations
OperatorExampleNameAlternate
construction
verticesedgesfacesDescription
T0 , t0{4,3}"Seed" vefSeed form
R = T1, t1{4,3}rectify a e2ef+vsame as ambo, new vertices are added mid-edges, new faces centered on original vertices.
Vertices are all valence 4.
T2 , t2{4,3}dual
birectify
dfevdual of the seed polyhedron - each vertex creates a new face
T = T0,1, t0,1{4,3}truncatet 2e3ev+ftruncate all vertices.
T1,2 , t1,2{4,3} bitruncate z = td 2e3ev+fsame as zip
RR = T0,2, t0,2{4,3}cantellate aa=e 2e4ev+e+fsame as expand
TR = T0,1,2, t0,1,2{4,3}cantitruncate ta4e6ev+e+fsame as bevel

Semi-operators

The snub cube is constructed as one of two halves of a truncated cuboctahedron. sr{4,3} = SRC = HTRC.

.

The polyhedra F1bC and F2bC are not identical, and can retain full octahedral symmetry in general.

Coxeter's semi or demi operator, H for Half, reduces faces into half as many sides, and quadrilateral faces into digons, with two coinciding edges, which may or may not be replaced by a single edge. For example a half cube, h{4,3}, also called a demicube, is HC, representing one of two tetrahedra. Ho reduces an ortho to ambo/Rectify.

Other semi-operators can be defined using the H operator. Conway calls Coxeter's Snub operation S, a semi-snub, defined as Ht. Conway's snub operator s is defined as SR. For example, SRC is a snub cube, sr{4,3}. Coxeter's snub octahedron, s{3,4} can be defined as SO, a pyritohedral symmetry construction of the regular icosahedron. It also is consistent with the Johnson solid snub square antiprism as SA4.

A semi-gyro operator, G, is defined as here dHt. This allows Conway's gyro g to be defined as GR. For example, GRC is a gyro-cube, gC or a pentagonal icositetrahedron. And GO defines a pyritohedron with pyritohedral symmetry, while gT, a gyro tetrahedron defines the same topological polyhedron with tetrahedral symmetry.

Both of these operators, S and G, require an even-valence seed polyhedra. In all of these semi-operations, there are two choices of alternated vertices within the half operator. These two construction are not topologically identical in the general case. For example HjC ambiguously defines either a cube or octahedron, depending on which set of vertices are taken.

Other operators only apply to polyhedra with all even-sided faces. The simplest is the semi-join operator, as the conjugate operator of half, dHd.

A semi-ortho operator, F, is a conjugate operator to semi-snub. It adds a vertex in the center of the faces, and bisects all edges, but only connects new edges from each center to half of the edges, creating new hexagonal faces. Original square faces do not require the central vertex and need only a single edge across the face, creating pairs of pentagons. For example, a dodecahedron, tetartoid, can be constructed as FC.

A semi-expand operator, E, is defined as Htd or Hz. This creates triangular faces. For example, EC created a pyritohedral symmetry construction of a regular pseudoicosahedron.

Semi-operations on even-sided polyhedra
OperatorExample
(Cube seed)
NameAlternate
construction
verticesedgesfacesDescription
H = H1
H2
semi-ambo
Half
1 and 2
v/2e-f4f-f4+v/2Alternation, remove half vertices.
Quadrilateral faces (f4) are reduced to single edges.
I = I1
I2
semi-truncate
1 and 2
v/2+e2ef+v/2Truncate alternate vertices
semi-needle
1 and 2
dIv/2+f2ee+v/2Needle at alternate vertices
F = F1
F2
semi-ortho
Flex
1 and 2
dHtd = dHz
dSd
v+e+f-f4 3e-f4 e Dual of semi-expand: This creates new vertices in edge and face centers. 2n-gons are divided into n hexagons. Quadrilateral faces (f4) won't have center vertices, so 2 pentagonal faces are created.
E = E1
E2
semi-expand
Eco
1 and 2
Htd = Hz
dF = Sd
dGd
e 3e-f4 v+e+f-f4 Dual of semi-ortho: This create new triangular faces. Original faces will be replaced by half as many side polygons, with quadrilaterals (f4) reduced to single edges.
U = U1
U2
semi-lace
CUp
1 and 2
v+e 4e-f4 2e+f-f4 Augment faces by cupolae.
V = V1
V2
semi-lace
Anticup
3 and 4
v+e 5e-f4 3e+f-f4 Augment faces by anticupolae
semi-medial
1 and 2
XdH = XJd v+e+f 5e 3e Diagonal alternate medial
semi-medial
3 and 4
v+e+f 5e 3e Middle alternate medial
semi-bevel
1 and 2
dXdH = dXJd 3e 5e v+e+f Diagonal alternate bevel
semi-bevel
3 and 4
3e 5e v+e+f Middle alternate bevel
Semi-operations on even-valence polyhedra
OperatorExample
(Octahedron seed)
NameAlternate
construction
verticesedgesfacesDescription
J = J1
J2
semi-join
1 and 2
dHd v-v4+f/2e-v4f/2Conjugate of half, join operator on alternate faces. New vertices are created at valence-4 vertices can be removed.
4-valence vertices (v4) reduced to 2-valence vertices are replaced by a single edge.
semi-kis
1 and 2
dIdv+f/22ef/2+eKis alternate faces
semi-zip
1 and 2
Id f/2+e2ev+f/2Zip alternate faces
S = S1
S2
semi-snub
1 and 2
Ht
dFd
v-v4+e 3e-v4 f+e Dual of semi-gyro: Coxeter snub operation, rotating the original faces, and with new triangular faces in the gaps.
G = G1
G2
semi-gyro
1 and 2
dHt
dS = Fd
dEd
f+e 3e-v4 v-v4+e Dual of semi-snub: Create pentagonal and hexagonal faces along the original edges.
semi-medial
1 and 2
XdHd = XJ3e 5e v+e+f Medial across alternate faces
semi-bevel
1 and 2
dXdHd = dXJv+e+f 5e 3e Bevel on alternate faces

Subdivision

A subdivision operation divides original edges into n new edges and face interiors into smaller triangles or other polygons.

Square subdivision

The ortho operator can be applied in series for powers of two quad divisions. Other divisions can be produced by the product of factorized divisions. The propellor operator applied in sequence, in reverse chiral directions produces a 5-ortho division. If the seed polyhedron has nonquadrilaeral faces, they will be retained as smaller copies for odd-ortho operators.

Examples on a cube
Ortho o2=o o3 o4=o2 o5
=prp
o6=oo3 o7 o8=o3 o9=o32 o10=oo5
=oprp
Example
Vertices v v+e+fv+4ev+7e+fv+12ev+17e+fv+24ev+31e+fv+40e v+63e+f
Edges e 4e9e 16e25e36e49e64e81e128e
Faces f 2ef+4e 8ef+12e18ef+24e32ef+40e64e
Expand
(dual)
e2=e e3 e4=e2 e5
=dprp
e6=ee3 e7 e8=e3e9=e32e10=ee5
=doprp
Example

Chiral hexagonal subdivision

A whirl operation creates Goldberg polyhedra, G(2,1) with new hexagonal faces around each original vertex. Two sequential whirls create G(3,5). In general, a whirl can transform a G(a,b) into G(a+3b,2a-b) for a>b and the same chiral direction. If chiral directions are reversed, G(a,b) becomes G(2a+3b,a-2b) if a>=2b, and G(3a+b,2b-a) if a<2b. Higher n-whirls can be defined as G(n,n-1), and m,n-whirl G(m,n).

Whirl-n operators generate Goldberg polyhedra (n,n-1) and can be defined by dividing a seed polyhedron's edges into 2n-1 subedges as rings around brick pattern hexagons. Some can also be generated by composite operators with smaller Whirl-m,n operators.

The product of whirl-n and its reverse generates a (3n2-3n+1,0) Goldberg polyhedron. wrw generates (7,0) w3rw3 generates (19,0), w4rw4 generates (37,0), w5rw5 generates (61,0), and w6rw6 generates (91,0). The product of two whirl-n is ((n-1)(3n-1),2n-1) or (3n2-4n+1,2n-1). The product of wa by wb gives (3ab-2(a+b)+1,a+b-1), and wa by reverse wb is (3ab-a-2b+1,a-b) for a≥b.

The product of two identical whirl-n operators generates Goldberg ((n-1)(3n-1),2n-1). The product of a k-whirl and zip is (3k-2,1).

Whirl-n operators
NameSeedWhirlWhirl-3Whirl-4Whirl-5Whirl-6Whirl-7Whirl-8Whirl-9Whirl-10Whirl-11Whirl-12Whirl-13Whirl-14Whirl-15Whirl-16Whirl-17Whirl-18Whirl-19Whirl-20Whirl-n
Operator
(Composite)
- w=w2w3w4w5w6
wrw3,1
w7w8
w3,1w3,1
w9
ww5,1
w10w11w12w13
ww7,2
w14w15w16
ww9,2
w17
w3w6,1
w18w19
w3,1w7,3
w20
ww11,3
wn
Goldberg (1,0)(2,1)(3,2)(4,3)(5,4)(6,5)(7,6)(8,7)(9,8)(10,9)(11,10)(12,11)(13,12)(14,13)(15,14)(16,15)(17,16)(18,17)(19,18)(20,19)(n,n-1)
T
composite
1719376191
7×13
127169
13×13
217
7×31
271331397469
7×67
547631721
7×103
817
19×43
9191027
13×79
1141
7×163
3n(n-1)+1
Example
Vertices vv+4ev+12ev+24ev+40ev+60ev+84ev+112ev+144ev+180ev+220ev+264ev+312ev+364ev+420ev+480ev+544ev+612ev+684ev+760e v+2n(n-1)e
Edges e7e19e37e61e91e127e169e217e271e331e397e469e547e631e721e817e919e1027e1141e e+3n(n-1)e
Faces ff+2ef+6ef+12ef+20ef+30ef+42ef+56ef+72ef+90ef+110ef+132ef+156ef+182ef+210ef+240ef+272ef+306ef+342ef+380e f+n(n-1)e
wnwn (1,0)(5,3)(16,5)(33,7) (56,9) (85,11) (120,13) (161,15) (208,17) (261,19) (320,21) (385,23) (456,25) (533,27) (616,29) (705,31) (800,33) (901,35) (1008,37) (1121,39) ((n-1)(3n-1),2n-1)
wnrwn (1,0)(7,0)(19,0)(37,0)(61,0)(91,0)(127,0)(169,0)(217,0)(271,0)(331,0)(397,0)(469,0)(547,0)(631,0)(721,0)(817,0)(919,0)(1027,0)(1141,0)(1+3n(n-1),0)
wnz (1,1)(4,1)(7,1)(10,1)(13,1)(16,1)(19,1)(22,1)(25,1)(28,1)(31,1)(34,1)(37,1)(40,1)(43,1)(46,1)(49,1)(52,1)(55,1)(58,1)(3n-2,1)

Triangulated subdivision

Triangular subdivisions u1 to u6 on a square face, repeat their structure in intervals of 3 with new layers of triangles

An operation un divides faces into triangles with n-divisions along each edge, called an n-frequency subdivision in Buckminster Fuller's geodesic polyhedra.[2]

Conway polyhedron operators can construct many of these subdivisions.

If the original faces are all triangles, the new polyhedra will also have all triangular faces, and create triangular tilings within each original face. If the original polyhedra has higher polygons, all new faces won't necessarily be triangles. In such cases a polyhedron can first be kised, with new vertices inserted in the center of each face.

Subdivisions on a cube example
Operatoru1u2
=u
u3
=x
u4
=uu
u5u6
=ux
u7
=vrv
u8
=uuu
u9
=xx
Example
Conway C uC xC uuC u5C uxC vrvC uuuC xxC
Vertices vv+ev+e+fv+4ev+8ev+11e+fv+16ev+21ev+26e+f
Edges e4e9e16e25e36e49e64e81e
Faces ff+2e7ef+8ef+16e24ef+32ef+42e54e
Full triangulation
Operatoru1ku2k
=uk
u3k
=xk
u4k
=uuk
u5ku6k
=uxk
u7k
=vrvk
u8k
=uuuk
u9k
=xxk
Example
Conway kC ukC xkC uukC u5kC uxkC vrvkC uuukC xxkC
Goldberg dual{3,n+}1,1{3,n+}2,2{3,n+}3,3{3,n+}4,4{3,n+}5,5{3,n+}6,6{3,n+}7,7{3,n+}8,8{3,n+}9,9

Geodesic polyhedra

Conway operations can duplicate some of the Goldberg polyhedra and geodesic duals. The number of vertices, edges, and faces of Goldberg polyhedron G(m,n) can be computed from m and n, with T = m2 + mn + n2 = (m + n)2  mn as the number of new triangles in each subdivided triangle. (m,0) and (m,m) constructions are listed below from Conway operators.

Class I

For Goldberg duals, an operator uk is defined here as dividing faces with k edge subdivisions, with Conway u = u2, while its conjugate operator, dud is chamfer, c. This operator is used in computer graphics, loop subdivision surface, as recursive iterations of u2, doubling each application. The operator u3 is given a Conway operator kt=x, and its conjugate operator y=dxd=tk. The product of two whirl operators with reverse chirality, wrw or ww, produces 7 subdivisions as Goldberg polyhedron G(7,0), thus u7=vrv. Higher subdivision and whirl operations in chiral pairs can construct more class I forms. w(3,1)rw(3,1) gives Goldberg G(13,0). w(3,2)rw(3,2) gives G(19,0).

Class I: Subdivision operations on an icosahedron as geodesic polyhedra
(m,0)(1,0)(2,0)(3,0)(4,0)(5,0)(6,0)(7,0)(8,0)(9,0)(10,0)(11,0)(12,0)(13,0)(14,0)(15,0)(16,0)
T 1 4 9 162536496481100121144169196225256
Operation
Composite
u1 u2=u
=dcd
u3=x
=kt
u4
=u22
=dccd
u5 u6=u2u3
=dctkd
u7
=vv
=dwrwd
u8=u23
=dcccd
u9=u32
=ktkt
u10=u2u5 u11 u12=u22u3
=dccdkt
u13
v3,1v3,1
u14=u2u7
=uvv
=dcwrwd
u15= u3u5
=u5x
u16=u24
=dccccd
Face
triangle
Icosahedron
Conway
Geodesic

I
{3,5+}1,0

uI=k5aI
{3,5+}2,0

xI=ktI
{3,5+}3,0

u2I
{3,5+}4,0

 
{3,5+}5,0

uxI
{3,5+}6,0

vrvI
{3,5+}7,0

u3I
{3,5+}8,0

x2I
{3,5+}9,0

 
{3,5+}10,0

 
{3,5+}11,0

u2xI
{3,5+}12,0

 
{3,5+}13,0

uvrvI
{3,5+}14,0

 
{3,5+}15,0

u4I
{3,5+}16,0
Dual operator c y
=tk
cc c5 cy
=ctk
ww
=wrw
ccc y2
=tktk
cc5 c11 ccy
=cctk
w3,1w3,1 cww
=cwrw
c5y cccc
Dodecahedron
Conway
Goldberg

D
{5+,3}1,0

cD
{5+,3}2,0

yD
{5+,3}3,0

ccD
{5+,3}4,0

c3D
{5+,3}5,0

cyD
{5+,3}6,0

wrwD
{5+,3}7,0

cccD
{5+,3}8,0

y2D
{5+,3}9,0

cc5D
{5+,3}10,0

c11D
{5+,3}11,0

ccyD
{5+,3}12,0

w3,1rw3,1D
{5+,3}13,0

cwrwD
{5+,3}14,0

c5yD
{5+,3}15,0

ccccD
G{5+,3}16,0
Class II

Orthogonal subdivision can also be defined, using operator n=kd. The operator transforms geodesic polyhedron (a,b) into (a+2b,a-b), for a>b. It transforms (a,0) into (a,a), and (a,a) into (3a,0). The operator z=dk does the same for the Goldberg polyhedra.

This is also called a Triacon method, dividing into subtriangles along their height, so they require an even number of triangles along each edge.

Class II: Orthogonal subdivision operations
(m,m)(1,1)(2,2)(3,3)(4,4)(5,5)(6,6)(7,7)(8,8)(9,9)(10,10)(11,11)(12,12)(13,13)(14,14)(15,15)(16,16)
T=
m2×3
3
1×3
12
4×3
27
3×3
48
24×3
75
25×3
108
36×3
147
49×3
192
64×3
243
81×3
300
100×3
363
121×3
432
144×3
507
169×3
588
196×3
675
225×3
768
256×3
Operation u1n
n
=kd
u2n
=un
=dct
u3n
=xn
=ktkd
u4n
=u22n
=dcct
u5n u6n
=u2=u3n
=dctkt
u7n
=vvn
=dwrwt
u8n
=u23n
=dccct
u9n
=u32n
=ktktkd
u10n
=u2u5n
u11n u12n
=u22u3n
=dcctkt
u13n u14n
=u2u7n
=dcwrwt
u15n
=u3u5n
u16n
=u24n
=dcccct
Face
triangle
Icosahedron
Conway
Geodesic

nI
{3,5+}1,1

unI
{3,5+}2,2

xnI
{3,5+}3,3

u2nI
{3,5+}4,4

 
{3,5+}5,5

uxnI
{3,5+}6,6

vrvnI
{3,5+}7,7

u3nI
{3,5+}8,8

x2nI
{3,5+}9,9

{3,5+}10,10

{3,5+}11,11

u2xnI
{3,5+}12,12

{3,5+}13,13

dcwrwdnI
{3,5+}14,14

{3,5+}15,15

u4nI
{3,5+}16,16
Dual operator z
=dk
cz
=cdk
yz
=tkdk
c2z
=ccdk
c5z cyz
=ctkdk
wwz
=wrwdk
c3z
=cccdk
y2z
=tktkdk
cc5z c11z c2yz
=c2tkdk
c13z cwwz
=cwrwdk
c3c5z c4z
=ccccdk
Dodecahedron
Conway
Goldberg

zD
{5+,3}1,1

czD
{5+,3}2,2

yzD
{5+,3}3,3

cczD
{5+,3}4,4

 
{5+,3}5,5

cyzD
{5+,3}6,6

wrwzD
{5+,3}7,7

c3zD
{5+,3}8,8

y2zD
{5+,3}9,9

{5+,3}10,10

G{5+,3}11,11

ccyzD
{5+,3}12,12

{5+,3}13,13

cwrwzD
G{5+,3}14,14

{5+,3}15,15

cccczD
{5+,3}16,16
Class III

Most geodesic polyhedra and dual Goldberg polyhedra G(n,m) can't be constructed from derived Conway operators. The whirl operation creates Goldberg polyhedra, G(2,1) with new hexagonal faces around each original vertex, and n-whirl genereates G(n,n-1). On icosahedral symmetry forms, t5g is equivalent to whirl in this case. The v=volute operation represents the triangular subdivision dual of whirl. On icosahedral forms it can be made by the derived operator k5s, a pentakis snub.

Two sequential whirls create G(3,5). In general, a whirl can transform a G(a,b) into G(a+3b,2a-b) for a>b and the same chiral direction. If chiral directions are reversed, G(a,b) becomes G(2a+3b,a-2b) if a>=2b, and G(3a+b,2b-a) if a<2b.

Class III: Unequal subdivision operations
Operation
Composite
v2,1
=v
v3,1v3,2=v3v4,1
=vn
v4,2
=vu
v5,1v4,3=v4v5,2
=v3n
v6,1v6,2
=v3,1u
v5,3
=vv
v7,1
=v3n
v5,4=v5v6,3
=vx
v7,2
T 713 1921
7×3
28
7×4
313739
13×3
4352
13×4
49
7×7
57
19×3
6163
9×7
67
Face
triangle
Icosahedron
Conway
Geodesic

vI
{3,5+}2,1

v3,1I
{3,5+}3,1

v3I
{3,5+}3,2

vnI
{3,5+}4,1

vuI
{3,5+}4,2

{3,5+}5,1

v4I
{3,5+}4,3

v3nI
{3,5+}5,2

{3,5+}6,1

v3,1uI
{3,5+}6,2

vvI
{3,5+}5,3

v3nI
{3,5+}7,1

v5I
{3,5+}5,4

vxI
{3,5+}6,3

v7,2I
{3,5+}7,2
Operator w w3,1w3wzwcw5,1w4 w3,1zw6,1w3,1c www3zw5wyw7,2
Dodecahedron
Conway

wD
{5+,3}2,1

w3,1D
{5+,3}3,1

w3D
{5+,3}3,2

wzD
{5+,3}4,1

wcD
{5+,3}4,2

w5,1D
{5+,3}5,1

w4D
{5+,3}4,3

w3zD
{5+,3}5,2

{5+,3}6,1

w3,1cD
{5+,3}6,2

wwD
{5+,3}5,3

w3zD
{5+,3}7,1

w5D
{5+,3}5,4

wyD
{5+,3}6,3

w7,2D
{5+,3}7,2
More class III: Unequal subdivision operations
Operation
Composite
v8,1 v6,4
=v3u
v7,3 v8,2
=wcz
v6,5=v6
=vrv3,1
v9,1
=vv3,1
v7,4 v8,3 v9,2 v7,5 v10,1
=v4n
v8,4
=vuu
v9,3
=v3,1x
v7,6=v7 v8,6
v4u
T 7376
19×4
7984
7×4×3
91
13×7
9397103109111
37×3
112
7×4×4
117
13×9
127148
37×4
Face
triangle
Icosahedron
Conway
Geodesic

v8,1I
{3,5+}8,1

v3uI
{3,5+}6,4

v7,3I
{3,5+}7,3

vunI
{3,5+}8,2

vv3,1I
{3,5+}6,5

vrv3,1I
{3,5+}9,1

v7,4I
{3,5+}7,4

v8,3I
{3,5+}8,3

v9,2I
{3,5+}9,2

v7,5I
{3,5+}7,5

v4nI
{3,5+}10,1

vuuI
{3,5+}8,4

v3,1xI
{3,5+}9,3

v7I
{3,5+}7,6

v4uI
{3,5+}8,6
Operator w8,1 wrw3,1 w7,3 w3,1c wcz w3,1w w7,4 w8,3 w9,2 w7,5 w4z wcc w3,1y w7 w4c
Dodecahedron
Conway

w8,1D
{5+,3}8,1

w3cD
{5+,3}6,4

w7,3D
{5+,3}7,3

wczD
{5+,3}8,2

ww3,1D
{5+,3}6,5

wrw3,1D
{5+,3}9,1

w7,4D
{5+,3}7,4

w8,3D
{5+,3}8,3

w9,2D
{5+,3}9,2

w7,5D
{5+,3}7,5

w4zD
{5+,3}10,1

wccD
{5+,3}8,4

w3,1yD
{5+,3}9,3

w7D
{5+,3}7,6

w4cD
{5+,3}8,6

Example polyhedra by symmetry

Iterating operators on simple forms can produce progressively larger polyhedra, maintaining the fundamental symmetry of the seed element.

Tetrahedral symmetry

Octahedral symmetry

Chiral

Icosahedral symmetry

Chiral

Dihedral symmetry

Toroidal symmetry

Torioidal tilings exist on the flat torus on the surface of a duocylinder in four dimensions but can be projected down to three dimensions as an ordinary torus. These tilings are topologically similar subsets of the Euclidean plane tilings.

Euclidean square symmetry

Euclidean triangular symmetry

See also

References

  1. http://mathworld.wolfram.com/Cumulation.html
  2. Anthony Pugh, Polyhedra: a visual approach, (1976), Chapter 6, Geodesic polyhedra, p.63

(truncate)

(ambo)

(kis)

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.