Difference between revisions of "Static symmetry"
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== On a square grid == | == On a square grid == | ||
[[File: | [[File:Hickerson_and_Catagolue_symmetries.png|center|frame|Overview of symmetries (excluding D8_2).]] | ||
The directed graph above shows how the various static symmetries are related to each other. Each downward arrow corresponds to the removal of either a rotational symmetry or a line of reflection. | |||
For an overview of static symmetries in both Hickerson notation and [[Catagolue]] notation, see [[Table of equivalent static symmetries]] or the discussion in the [[Kinetic_symmetry#Kinetic_symmetry_naming_system|kinetic symmetry]] article. | |||
=== Rotational === | === Rotational === | ||
<div class="mw-collapsible | <div class="mw-collapsible"> | ||
In Catagolue notation, rotational symmetries are prefixed with "C", referring to the cyclic groups.<ref>{{LinkWikipedia|Cyclic_group|name=Cyclic group|nobullet=nobullet}}</ref> | |||
<div class="mw-collapsible-content"> | <div class="mw-collapsible-content"> | ||
| Line 18: | Line 22: | ||
<center>{{Sym-demo | <center>{{Sym-demo | ||
|rle = x = 16, y = 16, rule = B/ | |rle = x = 16, y = 16, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o! | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o! | ||
| Line 34: | Line 38: | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$31o | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$31o | ||
| Line 46: | Line 49: | ||
|caption = C2_1 symmetry}} | |caption = C2_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 32, rule = B/ | |rle = x = 31, y = 32, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | ||
| Line 56: | Line 59: | ||
|caption = C2_2 symmetry}} | |caption = C2_2 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 32, rule = B/ | |rle = x = 32, y = 32, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | ||
| Line 74: | Line 77: | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S01234V | ||
31o$o14bo14bo$o14bo14bo$o3b2o4b2o3bo3b3o3b2o3bo$o2bo2bo2bo2bo2bo2b4o2b | 31o$o14bo14bo$o14bo14bo$o3b2o4b2o3bo3b3o3b2o3bo$o2bo2bo2bo2bo2bo2b4o2b | ||
o2bo2bo$o2bo2bo2bo2bo2bo2b4o2bo2bo2bo$o3b2o4b2o3bo3b3o3b2o3bo$o14bo5bo | o2bo2bo$o2bo2bo2bo2bo2bo2b4o2bo2bo2bo$o3b2o4b2o3bo3b3o3b2o3bo$o14bo5bo | ||
| Line 89: | Line 91: | ||
|caption = C4_1 symmetry}} | |caption = C4_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 32, rule = B/ | |rle = x = 32, y = 32, rule = B/S01234V | ||
32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b3o3b2o3bo$o2bo2bo2bo2bo2b2o2b | 32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b3o3b2o3bo$o2bo2bo2bo2bo2b2o2b | ||
4o2bo2bo2bo$o2bo2bo2bo2bo2b2o2b4o2bo2bo2bo$o3b2o4b2o3b2o3b3o3b2o3bo$o | 4o2bo2bo2bo$o2bo2bo2bo2bo2b2o2b4o2bo2bo2bo$o3b2o4b2o3b2o3b3o3b2o3bo$o | ||
| Line 107: | Line 109: | ||
=== Reflectional === | === Reflectional === | ||
<div class="mw-collapsible | <div class="mw-collapsible"> | ||
In Catagolue notation, reflectional symmetries are prefixed with "D", referring to the dihedral groups.<ref>{{LinkWikipedia|Dihedral_group|name=Dihedral group|nobullet=nobullet}}</ref> | |||
<div class="mw-collapsible-content"> | <div class="mw-collapsible-content"> | ||
| Line 115: | Line 117: | ||
* '''D2_+''' The line is orthogonal. There are two sub-possibilities: | * '''D2_+''' The line is orthogonal. There are two sub-possibilities: | ||
** '''D2_+1''' The line bisects a row of cells. The bounding rectangle is odd by any. | ** '''D2_+1''' The line bisects a row of cells. The bounding rectangle is odd by any. Example: [[Hat]] | ||
** '''D2_+2''' The line lies between two rows of cells. The bounding rectangle is even by any. | ** '''D2_+2''' The line lies between two rows of cells. The bounding rectangle is even by any. Example: [[Frutterfly]] | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 16, y = 31, rule = B/ | |rle = x = 16, y = 31, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | ||
| Line 130: | Line 131: | ||
|caption = D2_+1 symmetry}} | |caption = D2_+1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 16, y = 32, rule = B/ | |rle = x = 16, y = 32, rule = B/S01234V | ||
16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | 16o$o14bo$o14bo$o3b2o4b2o3bo$o2bo2bo2bo2bo2bo$o2bo2bo2bo2bo2bo$o3b2o4b | ||
2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | 2o3bo$o14bo$o14bo$o2b10o2bo$o2b4o8bo$o2b4o8bo$o3b2o9bo$o14bo$o14bo$16o | ||
| Line 141: | Line 142: | ||
|} | |} | ||
* '''D2_x''' The line is diagonal. | * '''D2_x''' The line is diagonal. Example: [[Elevener]] | ||
<center>{{Sym-demo | <center>{{Sym-demo | ||
|rle = x = 16, y = 16, rule = B/ | |rle = x = 16, y = 16, rule = B/S01234V | ||
16o$o14bo$o14bo$o7bo6bo$o6bobo5bo$o7bo3bo2bo$o11bo2bo$o3bo7bo2bo$o2bob | 16o$o14bo$o14bo$o7bo6bo$o6bobo5bo$o7bo3bo2bo$o11bo2bo$o3bo7bo2bo$o2bob | ||
o6bo2bo$o3bo6bo3bo$o9bo4bo$o8bo5bo$o4b4o6bo$o14bo$o14bo$16o! | o6bo2bo$o3bo6bo3bo$o9bo4bo$o8bo5bo$o4b4o6bo$o14bo$o14bo$16o! | ||
| Line 155: | Line 156: | ||
* '''D4_+''': The lines are orthogonal. There are three sub-possibilities: | * '''D4_+''': The lines are orthogonal. There are three sub-possibilities: | ||
** '''D4_+1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. | ** '''D4_+1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: [[Dead spark coil]] | ||
** '''D4_+2''': Rotation around the midpoint of a side of a cell. The bounding rectangle is even by odd. | ** '''D4_+2''': Rotation around the midpoint of a side of a cell. The bounding rectangle is even by odd. Example: [[Honeycomb]] | ||
** '''D4_+4''': Rotation around a corner of a cell. The bounding rectangle is even by even. | ** '''D4_+4''': Rotation around a corner of a cell. The bounding rectangle is even by even. Example: [[A for all]] | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S01234V | ||
31o$o14bo14bo$o14bo14bo$o3b2o4b2o3bo3b2o4b2o3bo$o2bo2bo2bo2bo2bo2bo2bo | 31o$o14bo14bo$o14bo14bo$o3b2o4b2o3bo3b2o4b2o3bo$o2bo2bo2bo2bo2bo2bo2bo | ||
2bo2bo2bo$o2bo2bo2bo2bo2bo2bo2bo2bo2bo2bo$o3b2o4b2o3bo3b2o4b2o3bo$o14b | 2bo2bo2bo$o2bo2bo2bo2bo2bo2bo2bo2bo2bo2bo$o3b2o4b2o3bo3b2o4b2o3bo$o14b | ||
| Line 174: | Line 174: | ||
|caption = D4_+1 symmetry}} | |caption = D4_+1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 31, rule = B/ | |rle = x = 32, y = 31, rule = B/S01234V | ||
32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b2o4b2o3bo$o2bo2bo2bo2bo2b2o2b | 32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b2o4b2o3bo$o2bo2bo2bo2bo2b2o2b | ||
o2bo2bo2bo2bo$o2bo2bo2bo2bo2b2o2bo2bo2bo2bo2bo$o3b2o4b2o3b2o3b2o4b2o3b | o2bo2bo2bo2bo$o2bo2bo2bo2bo2b2o2bo2bo2bo2bo2bo$o3b2o4b2o3b2o3b2o4b2o3b | ||
| Line 187: | Line 187: | ||
|caption = D4_+2 symmetry}} | |caption = D4_+2 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 32, rule = B/ | |rle = x = 32, y = 32, rule = B/S01234V | ||
32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b2o4b2o3bo$o2bo2bo2bo2bo2b2o2b | 32o$o14b2o14bo$o14b2o14bo$o3b2o4b2o3b2o3b2o4b2o3bo$o2bo2bo2bo2bo2b2o2b | ||
o2bo2bo2bo2bo$o2bo2bo2bo2bo2b2o2bo2bo2bo2bo2bo$o3b2o4b2o3b2o3b2o4b2o3b | o2bo2bo2bo2bo$o2bo2bo2bo2bo2b2o2bo2bo2bo2bo2bo$o3b2o4b2o3b2o3b2o4b2o3b | ||
| Line 202: | Line 202: | ||
* '''D4_x''' The lines are diagonal. There are two sub-possibilities: | * '''D4_x''' The lines are diagonal. There are two sub-possibilities: | ||
** '''D4_x1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. | ** '''D4_x1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: [[Loaf siamese loaf]] | ||
** '''D4_x4''': Rotation around a corner of a cell. The bounding rectangle is even by even. | ** '''D4_x4''': Rotation around a corner of a cell. The bounding rectangle is even by even. Example: [[Long ship]] | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S01234V | ||
31o$o14bo14bo$o14bo14bo$o7bo6bo5b3o6bo$o6bobo5bo5bobo6bo$o7bo3bo2bo2bo | 31o$o14bo14bo$o14bo14bo$o7bo6bo5b3o6bo$o6bobo5bo5bobo6bo$o7bo3bo2bo2bo | ||
2b3o6bo$o11bo2bo2b2o10bo$o3bo7bo2bo2b2o5b3o2bo$o2bobo6bo2bo2b3o4bobo2b | 2b3o6bo$o11bo2bo2b2o10bo$o3bo7bo2bo2b2o5b3o2bo$o2bobo6bo2bo2b3o4bobo2b | ||
| Line 220: | Line 219: | ||
|caption = D4_x1 symmetry}} | |caption = D4_x1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 32, rule = B/ | |rle = x = 32, y = 32, rule = B/S01234V | ||
32o$o14b2o14bo$o14b2o14bo$o7bo6b2o5b3o6bo$o6bobo5b2o5bobo6bo$o7bo3bo2b | 32o$o14b2o14bo$o14b2o14bo$o7bo6b2o5b3o6bo$o6bobo5b2o5bobo6bo$o7bo3bo2b | ||
2o2bo2b3o6bo$o11bo2b2o2b2o10bo$o3bo7bo2b2o2b2o5b3o2bo$o2bobo6bo2b2o2b | 2o2bo2b3o6bo$o11bo2b2o2b2o10bo$o3bo7bo2b2o2b2o5b3o2bo$o2bobo6bo2b2o2b | ||
| Line 235: | Line 234: | ||
==== D8 ==== | ==== D8 ==== | ||
'''D8''': Symmetric under both reflection and 90° rotation. The reflection symmetry will be with respect to horizontal, vertical, and diagonal lines. There are | '''D8''': Symmetric under both reflection and 90° rotation. The reflection symmetry will be with respect to horizontal, vertical, and diagonal lines. There are two possibilities: | ||
* '''D8_1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. | * '''D8_1''': Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: [[Pulsar]] | ||
* '''D8_4''': Rotation around a corner of a cell. The bounding rectangle is even by even. Example: [[Lake 2]] | |||
* '''D8_4''': Rotation around a corner of a cell. The bounding rectangle is even by even. | |||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S01234V | ||
31o$o14bo14bo$o14bo14bo$o7bo6bo6bo7bo$o6bobo5bo5bobo6bo$o7bo3bo2bo2bo | 31o$o14bo14bo$o14bo14bo$o7bo6bo6bo7bo$o6bobo5bo5bobo6bo$o7bo3bo2bo2bo | ||
3bo7bo$o11bo2bo2bo11bo$o3bo7bo2bo2bo7bo3bo$o2bobo6bo2bo2bo6bobo2bo$o3b | 3bo7bo$o11bo2bo2bo11bo$o3bo7bo2bo2bo7bo3bo$o2bobo6bo2bo2bo6bobo2bo$o3b | ||
| Line 256: | Line 253: | ||
|caption = D8_1 symmetry}} | |caption = D8_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = 32, rule = B/S01234V | |||
|rle = x = 32, y = 32, rule = B/ | |||
32o$o14b2o14bo$o14b2o14bo$o7bo6b2o6bo7bo$o6bobo5b2o5bobo6bo$o7bo3bo2b | 32o$o14b2o14bo$o14b2o14bo$o7bo6b2o6bo7bo$o6bobo5b2o5bobo6bo$o7bo3bo2b | ||
2o2bo3bo7bo$o11bo2b2o2bo11bo$o3bo7bo2b2o2bo7bo3bo$o2bobo6bo2b2o2bo6bob | 2o2bo3bo7bo$o11bo2b2o2bo11bo$o3bo7bo2b2o2bo7bo3bo$o2bobo6bo2b2o2bo6bob | ||
| Line 281: | Line 266: | ||
|} | |} | ||
</div></div> | </div></div> | ||
== On a hexagonal or triangular grid == | == On a hexagonal or triangular grid == | ||
[[Hexagonal neighbourhood|Hexagonal]] and [[triangular neighbourhood|triangular]] grids have the same set of admissible symmetries as each other (by | [[File:Hexagonal symmetries.png|center|frame|Overview of hexagonal symmetries. Blue arrows correspond to non-normal subgroups.]] | ||
[[Hexagonal neighbourhood|Hexagonal]] and [[triangular neighbourhood|triangular]] grids have the same set of admissible symmetries as each other (by planar<ref>{{LinkMathworld|filename=DualTessellation.html|pagename=Dual tessellation}}</ref> or polytopic duality<ref>{{LinkWikipedia|Dual_polyhedron#Dual_polytopes_and_tessellations|name=Dual polyhedron|nobullet=nobullet}}</ref> - see also [[Schläfli symbol]]), but these are not the same symmetries as square grids. Due to how hexagonal and triangular grids are handled by programs such as [[Golly]] and [[LifeViewer]], they will also appear markedly different in these respects. C2, D2, and D4 symmetries are still compatible, but C4 symmetries become meaningless because the cells no longer have a side count that is perfectly divisible by 4. Other symmetries are exclusive to these alternative grids, as indicated below: | |||
* C1 | * C1 | ||
* C2_1 | * C2_1 | ||
* | * C2_2 | ||
* C3_1 | * C3_1 | ||
* C3_3 (unsupported by apgsearch) | * C3_3 (unsupported by apgsearch) | ||
| Line 326: | Line 289: | ||
[[apgsearch]] currently supports most higher symmetries for hexagonal rules; the rest (C3_3 and D6_3) will be added in a future version.<ref name="post66638" /> | [[apgsearch]] currently supports most higher symmetries for hexagonal rules; the rest (C3_3 and D6_3) will be added in a future version.<ref name="post66638" /> | ||
=== Rotational === | === Rotational === | ||
<div class="mw-collapsible | <div class="mw-collapsible"> | ||
Click on "Expand" to the right to view a list of hexagonal/triangular rotational symmetries. | Click on "Expand" to the right to view a list of hexagonal/triangular rotational symmetries. | ||
<div class="mw-collapsible-content"> | <div class="mw-collapsible-content"> | ||
| Line 338: | Line 299: | ||
<center>{{Sym-demo | <center>{{Sym-demo | ||
|rle = x = 16, y = | |rle = x = 16, y = 31, rule = B/S0123HT | ||
o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o2b2o6bo$o2bobo2bo3b | |||
o$o3b2o2bo4bo$o8bo4bo$o8bo5bo$bo8b2o3bo$2bo3b2o2b3o2bo$3bo2bobo2b2o2b | |||
|width = | o$4bo2b2o6bo$5bo9bo$6bo8bo$7bo7bo$8bo6bo$9bo5bo$10bo4bo$11bo3bo$12bo2b | ||
|height = | o$13bobo$14b2o$15bo! | ||
|width = 300 | |||
|height = 300 | |||
|caption = C1 symmetry | |caption = C1 symmetry | ||
}}</center> | }}</center> | ||
| Line 350: | Line 313: | ||
* '''C2_1''': Rotation around the center of a cell. | * '''C2_1''': Rotation around the center of a cell. | ||
* ''' | * '''C2_4''': Rotation around the midpoint of a side of a cell. | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S0123HT | ||
o14bo$2o13b2o$obo12bobo$o2bo11bo2bo$o3bo10bo3bo$o4bo9bo4bo$o5bo8bo5bo | |||
$o6bo7bo6bo$o7bo6bo7bo$o8bo5bo8bo$o9bo4bo9bo$o2b2o6bo3bo6b2o2bo$o2bob | |||
$ | o2bo3bo2bo2b2o2bobo2bo$o3b2o2bo4bobo2b3o2b2o3bo$o8bo4b2o3b2o8bo$o8bo5b | ||
o5bo8bo$bo8b2o3b2o4bo8bo$2bo3b2o2b3o2bobo4bo2b2o3bo$3bo2bobo2b2o2bo2b | |||
o3bo2bobo2bo$4bo2b2o6bo3bo6b2o2bo$5bo9bo4bo9bo$6bo8bo5bo8bo$7bo7bo6bo | |||
7bo$8bo6bo7bo6bo$9bo5bo8bo5bo$10bo4bo9bo4bo$11bo3bo10bo3bo$12bo2bo11b | |||
o2bo$13bobo12bobo$14b2o13b2o$15bo14bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
|caption = C2_1 symmetry}} | |caption = C2_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = | |rle = x = 32, y = 31, rule = B/S0123HT | ||
o15bo$2o14b2o$obo13bobo$o2bo12bo2bo$o3bo11bo3bo$o4bo10bo4bo$o5bo9bo5b | |||
o$o6bo8bo6bo$o7bo7bo7bo$o8bo6bo8bo$o9bo5bo9bo$o2b2o6bo4bo6b2o2bo$o2bo | |||
$ | bo2bo3bo3bo2b2o2bobo2bo$o3b2o2bo4bo2bo2b3o2b2o3bo$o8bo4bobo3b2o8bo$o8b | ||
o5b2o5bo8bo$bo8b2o3bobo4bo8bo$2bo3b2o2b3o2bo2bo4bo2b2o3bo$3bo2bobo2b2o | |||
2bo3bo3bo2bobo2bo$4bo2b2o6bo4bo6b2o2bo$5bo9bo5bo9bo$6bo8bo6bo8bo$7bo7b | |||
o7bo7bo$8bo6bo8bo6bo$9bo5bo9bo5bo$10bo4bo10bo4bo$11bo3bo11bo3bo$12bo2b | |||
o12bo2bo$13bobo13bobo$14b2o14b2o$15bo15bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
|caption = C2_4 | |caption = C2_4 symmetry}} | ||
|} | |} | ||
| Line 383: | Line 349: | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 46, y = 46, rule = B/ | |rle = x = 46, y = 46, rule = B/S0123HT | ||
o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o6b2o2bo$o2b2o2bobo2b | o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o6b2o2bo$o2b2o2bobo2b | ||
o$o2b3o2b2o3bo$o3b2o8bo$o5bo8bo$bo4bo8bo$2bo4bo2b2o3bo$3bo3bo2bobo2bo$ | o$o2b3o2b2o3bo$o3b2o8bo$o5bo8bo$bo4bo8bo$2bo4bo2b2o3bo$3bo3bo2bobo2bo$ | ||
| Line 398: | Line 363: | ||
|caption = C3_1 symmetry}} | |caption = C3_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = | |rle = x = 47, y = 47, rule = B/S0123HT | ||
o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o6b2o2bo$o2b2o2bobo2b | o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o6b2o2bo$o2b2o2bobo2b | ||
o$o2b3o2b2o3bo$o3b2o8bo$o5bo8bo$bo4bo8bo$2bo4bo2b2o3bo$3bo3bo2bobo2bo$ | o$o2b3o2b2o3bo$o3b2o8bo$o5bo8bo$bo4bo8bo$2bo4bo2b2o3bo$3bo3bo2bobo2bo | ||
4bo6b2o2bo$5bo9bo$6bo8bo$7bo7bo$8bo6bo$9bo5bo$10bo4bo$11bo3bo$ | $4bo6b2o2bo$5bo9bo$6bo8bo$7bo7bo$8bo6bo$9bo5bo$10bo4bo$11bo3bo$12bo2b | ||
13bobo$14b2o$ | o$13bobo$14b2o$15bo$32o$o14bobo14bo$o14bo2bo14bo$o5b2o7bo3bo14bo$o5bo | ||
bo6bo4bo7bo6bo$o6b2o6bo5bo7b2ob2o2bo$o2b2o10bo6bo8b4o2bo$o2bobo9bo7bo | |||
3b2o4b2o3bo$o3b2o4b2o3bo8bo2bobo9bo$o8b2o4bo9bo2b2o10bo$o7b2o5bo10bo6b | |||
2o6bo$o7b3o4bo11bo5bobo6bo$o8b2o4bo12bo5b2o7bo$o14bo13bo14bo$o14bo14b | |||
o14bo$16o15b16o! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
| Line 416: | Line 381: | ||
<center>{{Sym-demo | <center>{{Sym-demo | ||
|rle = x = 61, y = 61, rule = B/ | |rle = x = 61, y = 61, rule = B/S0123HT | ||
15bo$15b2o$15bobo$15bo2bo$15bo3bo$15bo4bo$15bo5bo$15bo6bo$15bo7bo$15bo | 15bo$15b2o$15bobo$15bo2bo$15bo3bo$15bo4bo$15bo5bo$15bo6bo$15bo7bo$15bo | ||
8bo$15bo9bo$15bo6b2o2bo$15bo2b2o2bobo2bo$15bo2b3o2b2o3bo$15bo3b2o8bo$ | 8bo$15bo9bo$15bo6b2o2bo$15bo2b2o2bobo2bo$15bo2b3o2b2o3bo$15bo3b2o8bo$ | ||
| Line 437: | Line 402: | ||
=== Reflectional === | === Reflectional === | ||
<div class="mw-collapsible | <div class="mw-collapsible"> | ||
Click on "Expand" to the right to view a list of hexagonal/triangular reflectional symmetries. | Click on "Expand" to the right to view a list of hexagonal/triangular reflectional symmetries. | ||
<div class="mw-collapsible-content"> | <div class="mw-collapsible-content"> | ||
| Line 444: | Line 409: | ||
'''D2''': There is line symmetry. There are two possibilities: | '''D2''': There is line symmetry. There are two possibilities: | ||
* '''D2_x''': Through the vertices of a cell. | * '''D2_x''': Through the vertices of a cell (diagonal). | ||
* '''D2_xo''': Through the edges of a cell. | * '''D2_xo''': Through the edges of a cell (orthogonal). | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 16, y = | |rle = x = 16, y = 31, rule = B/S0123HT | ||
o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o7bo$o8bo$o9bo$o2b2o2b2o2bo$o2bobob | |||
obo2bo$o3b2o2b2o3bo$o13bo$o14bo$bo13bo$2bo2bo6bo2bo$3bo2bo5bo2bo$4bo2b | |||
o4bo2bo$5bo2b5o2bo$6bo8bo$7bo7bo$8bo6bo$9bo5bo$10bo4bo$11bo3bo$12bo2b | |||
o$13bobo$14b2o$15bo! | |||
|width = 300 | |width = 300 | ||
|height = 300 | |height = 300 | ||
|caption = D2_x symmetry}} | |caption = D2_x symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = | |rle = x = 16, y = 31, rule = B/S0123HT | ||
o$2o$obo$o2bo$o3bo$o4bo$o5bo$o6bo$o4bo2bo$o5bo2bo$o2b2o2bo2bo$o2bobo2b | |||
o2bo$o3b2o3bo2bo$o8bo3bo$o9bo3bo$o9bo4bo$bo9bo3bo$2bo8bo3bo$3bo3b2o3b | |||
o2bo$4bo2bobo2bo2bo$5bo2b2o2bo2bo$6bo5bo2bo$7bo4bo2bo$8bo6bo$9bo5bo$10b | |||
o4bo$11bo3bo$12bo2bo$13bobo$14b2o$15bo! | |||
|width = 300 | |width = 300 | ||
|height = 300 | |height = 300 | ||
| Line 475: | Line 440: | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = B/ | |rle = x = 31, y = 31, rule = B/S0123HT | ||
o14bo$2o13b2o$obo12bobo$o2bo11bo2bo$o3bo10bo3bo$o4bo9bo4bo$o5bo8bo5bo | |||
$o6bo7bo6bo$o4bo2bo6bo2bo4bo$o5bo2bo5bo2bo5bo$o2b2o2bo2bo4bo2bo2b2o2b | |||
o$o2bobo2bo2bo3bo2bo2bobo2bo$o3b2o3bo2bo2bo2bo3b2o3bo$o8bo3bobo3bo8bo | |||
$o9bo3b2o3bo9bo$o9bo4bo4bo9bo$bo9bo3b2o3bo9bo$2bo8bo3bobo3bo8bo$3bo3b | |||
2o3bo2bo2bo2bo3b2o3bo$4bo2bobo2bo2bo3bo2bo2bobo2bo$5bo2b2o2bo2bo4bo2b | |||
o2b2o2bo$6bo5bo2bo5bo2bo5bo$7bo4bo2bo6bo2bo4bo$8bo6bo7bo6bo$9bo5bo8bo | |||
5bo$10bo4bo9bo4bo$11bo3bo10bo3bo$12bo2bo11bo2bo$13bobo12bobo$14b2o13b | |||
2o$15bo14bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
|caption = D4_x1 symmetry}} | |caption = D4_x1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 32, y = | |rle = x = 32, y = 31, rule = B/S0123HT | ||
o15bo$2o14b2o$obo13bobo$o2bo12bo2bo$o3bo11bo3bo$o4bo10bo4bo$o5bo9bo5b | |||
o$o6bo8bo6bo$o4bo2bo7bo2bo4bo$o5bo2bo6bo2bo5bo$o2b2o2bo2bo5bo2bo2b2o2b | |||
o$o2bobo2bo2bo4bo2bo2bobo2bo$o3b2o3bo2bo3bo2bo3b2o3bo$o8bo3bo2bo3bo8b | |||
o$o9bo3bobo3bo9bo$o9bo4b2o4bo9bo$bo9bo3bobo3bo9bo$2bo8bo3bo2bo3bo8bo$ | |||
3bo3b2o3bo2bo3bo2bo3b2o3bo$4bo2bobo2bo2bo4bo2bo2bobo2bo$5bo2b2o2bo2bo | |||
5bo2bo2b2o2bo$6bo5bo2bo6bo2bo5bo$7bo4bo2bo7bo2bo4bo$8bo6bo8bo6bo$9bo5b | |||
o9bo5bo$10bo4bo10bo4bo$11bo3bo11bo3bo$12bo2bo12bo2bo$13bobo13bobo$14b | |||
2o14b2o$15bo15bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
| Line 501: | Line 471: | ||
'''D6''': Symmetric under both reflection and 120° rotation. The reflection symmetry will be with respect to three lines. There are three possibilities: | '''D6''': Symmetric under both reflection and 120° rotation. The reflection symmetry will be with respect to three lines. There are three possibilities: | ||
* '''D6_1''': Rotation around the center of a cell with lines going through the | * '''D6_1''': Rotation around the center of a cell with lines going through the vertices of cells. | ||
* '''D6_1o''': Rotation around the center of a cell with lines going through the | * '''D6_1o''': Rotation around the center of a cell with lines going through the edges of cells. | ||
* '''D6_3''': Rotation around the corner of a cell. (unsupported by apgsearch) | * '''D6_3''': Rotation around the corner of a cell. (unsupported by apgsearch) | ||
{| style="margin-left: auto; margin-right: auto" | {| style="margin-left: auto; margin-right: auto" | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 46, y = 46, rule = B/ | |rle = x = 46, y = 46, rule = B/S0123HT | ||
16o14b16o$bo14bo13bo14bo$2bo14bo12bo14bo$3bo6b4o4bo11bo4b4o6bo$4bo5bo | |||
8bo10bo8bo5bo$5bo4bo9bo9bo9bo4bo$6bo3bo6b2o2bo8bo2b2o6bo3bo$7bo2bo6bo | |||
bo2bo7bo2bobo6bo2bo$8bo2bo6b2o3bo6bo3b2o6bo2bo$9bo2bo11bo5bo11bo2bo$10b | |||
$ | o2bo3b2o6bo4bo6b2o3bo2bo$11bo5bobo6bo3bo6bobo5bo$12bo5b2o7bo2bo7b2o5b | ||
o$13bo14bobo14bo$14bo14b2o14bo$15b31o$30b2o$30bobo$30bo2bo$30bo3bo$30b | |||
o4bo$30bo5bo$30bo6bo$30bo7bo$30bo8bo$30bo9bo$30bo2b2o2b2o2bo$30bo2bob | |||
obobo2bo$30bo3b2o2b2o3bo$30bo13bo$30bo14bo$31bo13bo$32bo2bo6bo2bo$33b | |||
o2bo5bo2bo$34bo2bo4bo2bo$35bo2b5o2bo$36bo8bo$37bo7bo$38bo6bo$39bo5bo$ | |||
40bo4bo$41bo3bo$42bo2bo$43bobo$44b2o$45bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
|caption = D6_1 symmetry}} | |caption = D6_1 symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = 31, y = 31, rule = | |rle = x = 31, y = 31, rule = B/S0123HT | ||
16o$2o14bo$obo14bo$o2bo4b5o5bo$o3bo8b2o4bo$o4bo9b2o3bo$o5bo3b2o5b2o2bo | 16o$2o14bo$obo14bo$o2bo4b5o5bo$o3bo8b2o4bo$o4bo9b2o3bo$o5bo3b2o5b2o2bo | ||
$o6bo2bobo6bo2bo$o2bo4bo2b2o7bo2bo$o2bo5bo11bo2bo$o2bo2b2o2bo7b2o2bo2b | $o6bo2bobo6bo2bo$o2bo4bo2b2o7bo2bo$o2bo5bo11bo2bo$o2bo2b2o2bo7b2o2bo2b | ||
| Line 533: | Line 503: | ||
|caption = D6_1o symmetry}} | |caption = D6_1o symmetry}} | ||
| {{Sym-demo | | {{Sym-demo | ||
|rle = x = | |rle = x = 47, y = 47, rule = B/S0123HT | ||
16o15b16o$bo14bo14bo14bo$2bo14bo13bo14bo$3bo6b4o4bo12bo4b4o6bo$4bo5bo | |||
8bo11bo8bo5bo$5bo4bo9bo10bo9bo4bo$6bo3bo6b2o2bo9bo2b2o6bo3bo$7bo2bo6b | |||
obo2bo8bo2bobo6bo2bo$8bo2bo6b2o3bo7bo3b2o6bo2bo$9bo2bo11bo6bo11bo2bo$ | |||
$ | 10bo2bo3b2o6bo5bo6b2o3bo2bo$11bo5bobo6bo4bo6bobo5bo$12bo5b2o7bo3bo7b2o | ||
5bo$13bo14bo2bo14bo$14bo14bobo14bo$15b32o$31bo$31b2o$31bobo$31bo2bo$31b | |||
o3bo$31bo4bo$31bo5bo$31bo6bo$31bo7bo$31bo8bo$31bo9bo$31bo2b2o2b2o2bo$ | |||
31bo2bobobobo2bo$31bo3b2o2b2o3bo$31bo13bo$31bo14bo$32bo13bo$33bo2bo6b | |||
o2bo$34bo2bo5bo2bo$35bo2bo4bo2bo$36bo2b5o2bo$37bo8bo$38bo7bo$39bo6bo$ | |||
40bo5bo$41bo4bo$42bo3bo$43bo2bo$44bobo$45b2o$46bo! | |||
|width = 400 | |width = 400 | ||
|height = 400 | |height = 400 | ||
| Line 551: | Line 522: | ||
<center>{{Sym-demo | <center>{{Sym-demo | ||
|rle = x = 61, y = 61, rule = B/ | |rle = x = 61, y = 61, rule = B/S0123HT | ||
15bo$15b2o$15bobo$15bo2bo$15bo3bo$15bo4bo$15bo5bo$15bo6bo$15bo7bo$15bo | 15bo$15b2o$15bobo$15bo2bo$15bo3bo$15bo4bo$15bo5bo$15bo6bo$15bo7bo$15bo | ||
8bo$15bo2b5o2bo$15bo2bo4bo2bo$15bo2bo5bo2bo$15bo2bo6bo2bo$15bo13bo$16o | 8bo$15bo2b5o2bo$15bo2bo4bo2bo$15bo2bo5bo2bo$15bo2bo6bo2bo$15bo13bo$16o | ||
| Line 570: | Line 541: | ||
|caption = D12 symmetry}}</center> | |caption = D12 symmetry}}</center> | ||
</div></div> | </div></div> | ||
== Higher Dimensions == | |||
The symmetries for the cubic grid are listed at [[Cubic grid symmetries]]. | |||
== References == | == References == | ||
| Line 579: | Line 553: | ||
|author = GUYTU6J | |author = GUYTU6J | ||
|date = December 13, 2021 | |date = December 13, 2021 | ||
}}</ref> | }}</ref> | ||
<ref name="post66638">{{LinkForumThread | <ref name="post66638">{{LinkForumThread | ||
| Line 593: | Line 560: | ||
|author = Adam P. Goucher | |author = Adam P. Goucher | ||
|date = December 20, 2018 | |date = December 20, 2018 | ||
}}</ref> | }}</ref> | ||
</references> | </references> | ||
Latest revision as of 09:15, 28 February 2026
A static symmetry[1] refers to the combined rotational and reflectional symmetries of an arrangement of cells on a grid. Most isotropic rules preserve all such symmetries.
This page specifically only covers purely geometric symmetries. Other preserved attributes which are not necessarily geometrical symmetries, notably gutters, are compiled on the Minor static symmetries page. Symmetries which apply to periodic objects, such as still lifes, oscillators and spaceships, which also includes time symmetries, are listed on the Kinetic symmetry page.
Basic theory
The Life transition rule, like that of any isotropic cellular automaton, is invariant under valid reflections and rotations. That is, the change in state of a cell remains the same if its neighbourhood is rotated or reflected. This implies there are symmetries which if present in a pattern are present in all its successors. Note that the converse is not true: a pattern need not have the full symmetry of one of its successor states.
On a square grid
The directed graph above shows how the various static symmetries are related to each other. Each downward arrow corresponds to the removal of either a rotational symmetry or a line of reflection.
For an overview of static symmetries in both Hickerson notation and Catagolue notation, see Table of equivalent static symmetries or the discussion in the kinetic symmetry article.
Rotational
In Catagolue notation, rotational symmetries are prefixed with "C", referring to the cyclic groups.[2]
C1
C1: Symmetric under 360° rotation. This is essentially no symmetry at all. Example: Eater 1
| C1 symmetry |
C2
C2: Symmetric under 180° rotation. There are three possibilities:
- C2_1: Rotation around the center of a cell. The bounding rectangle of a C2_1 pattern is odd by odd. Example: Long snake
- C2_2: Rotation around the midpoint of a side of a cell. The bounding rectangle is even by odd. Example: Aircraft carrier
- C2_4: Rotation around a corner of a cell. The bounding rectangle is even by even. Example: Snake
|
|
|
C4
C4: Symmetric under 90° rotation. There are two possibilities:
- C4_1: Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: Shuriken
- C4_4: Rotation around a corner of a cell. The bounding rectangle is even by even. Example: Quad
|
|
C4 tends to produce record diehards and megasized soups compared to other symmetries.
Reflectional
In Catagolue notation, reflectional symmetries are prefixed with "D", referring to the dihedral groups.[3]
D2
D2: Symmetric under reflection through a line. There are two possibilities:
- D2_+ The line is orthogonal. There are two sub-possibilities:
- D2_+1 The line bisects a row of cells. The bounding rectangle is odd by any. Example: Hat
- D2_+2 The line lies between two rows of cells. The bounding rectangle is even by any. Example: Frutterfly
|
|
- D2_x The line is diagonal. Example: Elevener
| D2_x symmetry |
D4
D4: Symmetric under both reflection and 180° rotation. The reflection symmetry will be with respect to two lines. There are two possibilities:
- D4_+: The lines are orthogonal. There are three sub-possibilities:
- D4_+1: Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: Dead spark coil
- D4_+2: Rotation around the midpoint of a side of a cell. The bounding rectangle is even by odd. Example: Honeycomb
- D4_+4: Rotation around a corner of a cell. The bounding rectangle is even by even. Example: A for all
|
|
|
- D4_x The lines are diagonal. There are two sub-possibilities:
- D4_x1: Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: Loaf siamese loaf
- D4_x4: Rotation around a corner of a cell. The bounding rectangle is even by even. Example: Long ship
|
|
D8
D8: Symmetric under both reflection and 90° rotation. The reflection symmetry will be with respect to horizontal, vertical, and diagonal lines. There are two possibilities:
- D8_1: Rotation around the center of a cell. The bounding rectangle is odd by odd. Example: Pulsar
- D8_4: Rotation around a corner of a cell. The bounding rectangle is even by even. Example: Lake 2
|
|
On a hexagonal or triangular grid
Hexagonal and triangular grids have the same set of admissible symmetries as each other (by planar[4] or polytopic duality[5] - see also Schläfli symbol), but these are not the same symmetries as square grids. Due to how hexagonal and triangular grids are handled by programs such as Golly and LifeViewer, they will also appear markedly different in these respects. C2, D2, and D4 symmetries are still compatible, but C4 symmetries become meaningless because the cells no longer have a side count that is perfectly divisible by 4. Other symmetries are exclusive to these alternative grids, as indicated below:
- C1
- C2_1
- C2_2
- C3_1
- C3_3 (unsupported by apgsearch)
- C6
- D2_xo
- D2_x
- D4_x1
- D4_x4
- D6_1
- D6_1o
- D6_3 (unsupported by apgsearch)
- D12
apgsearch currently supports most higher symmetries for hexagonal rules; the rest (C3_3 and D6_3) will be added in a future version.[6]
Rotational
Click on "Expand" to the right to view a list of hexagonal/triangular rotational symmetries.
C1
C1: Symmetric under 360° rotation. This is essentially no symmetry at all.
| C1 symmetry |
C2
C2: Symmetric under 180° rotation. There are two possibilities:
- C2_1: Rotation around the center of a cell.
- C2_4: Rotation around the midpoint of a side of a cell.
|
|
C3
C3: Symmetric under 120° rotation. There are two possibilities:
- C3_1: Rotation around the center of a cell.
- C3_3: Rotation around a corner of a cell. (unsupported by apgsearch)
|
|
C6
C6: Symmetric under 60° rotation.
| C6 symmetry |
Reflectional
Click on "Expand" to the right to view a list of hexagonal/triangular reflectional symmetries.
D2
D2: There is line symmetry. There are two possibilities:
- D2_x: Through the vertices of a cell (diagonal).
- D2_xo: Through the edges of a cell (orthogonal).
|
|
D4
D4: Symmetric under both reflection and 180° rotation. The reflection symmetry will be with respect to two lines. There are two possibilities:
- D4_x1: Rotation around the center of a cell.
- D4_x4: Rotation around the edges of a cell.
|
|
D6
D6: Symmetric under both reflection and 120° rotation. The reflection symmetry will be with respect to three lines. There are three possibilities:
- D6_1: Rotation around the center of a cell with lines going through the vertices of cells.
- D6_1o: Rotation around the center of a cell with lines going through the edges of cells.
- D6_3: Rotation around the corner of a cell. (unsupported by apgsearch)
|
|
|
D12
D12: Symmetric under both reflection and 60° rotation. The reflection symmetry will be with respect to six lines.
| D12 symmetry |
Higher Dimensions
The symmetries for the cubic grid are listed at Cubic grid symmetries.
References
- ↑ GUYTU6J (December 13, 2021). Re: Help with symmetries (discussion thread) at the ConwayLife.com forums
- ↑ Cyclic group at Wikipedia
- ↑ Dihedral group at Wikipedia
- ↑ Dual tessellation at Wolfram Mathworld
- ↑ Dual polyhedron at Wikipedia
- ↑ Adam P. Goucher (December 20, 2018). Re: apgsearch v4.0 (discussion thread) at the ConwayLife.com forums
External links
- Symmetric at the Life Lexicon
- Help with symmetries (discussion thread) at the ConwayLife.com forums

