Near-miss Johnson solid

In geometry, a near-miss Johnson solid is a strictly convex polyhedron whose faces are close to being regular polygons but some or all of which are not precisely regular. Thus, it fails to meet the definition of a Johnson solid, a polyhedron whose faces are all regular, though it "can often be physically constructed without noticing the discrepancy" between its regular and irregular faces.[1] The precise number of near misses depends on how closely the faces of such a polyhedron are required to approximate regular polygons. Some high symmetry near-misses are also symmetrohedra with some perfect regular polygon faces.

Examples
Name
Conway name		ImageVertex
configurations		VEFF3F4F5F6F8F10F12Symmetry
Truncated triangular bipyramid
t4dP3		2 (5.5.5)
12 (4.5.5)		1421936Dih3
order 12
Truncated triakis tetrahedron
t6kT		 4 (5.5.5)
24 (5.5.6)		 28 42 16     12 4       Td, [3,3]
order 24
Pentahexagonal pyritoheptacontatetrahedron 60 132 74 56 12 6 Th, [3+,4]
order 24
Chamfered cube
cC		 24 (4.6.6)
8 (6.6.6)		 32 48 18   6   12       Oh, [4,3]
order 48
-- 12 (5.5.6)
6 (3.5.3.5)
12 (3.3.5.5)		 30 54 26 12   12 2       D6h, [6,2]
order 24
-- 6 (5.5.5)
9 (3.5.3.5)
12 (3.3.5.5)		 27 51 26 14   12         D3h, [3,2]
order 12
Tetrated dodecahedron 4 (5.5.5)
12 (3.5.3.5)
12 (3.3.5.5)		 28 54 28 16   12         Td, [3,3]
order 24
Chamfered dodecahedron
cD		 60 (5.6.6)
20 (6.6.6)		 80 120 42     12 30       Ih, [5,3]
order 120
Rectified truncated icosahedron
atI		 60 (3.5.3.6)
30 (3.6.3.6)		 90 180 92 60   12 20       Ih, [5,3]
order 120
Truncated truncated icosahedron
ttI		 120 (3.10.12)
60 (3.12.12)		 180 270 92 60         12 20 Ih, [5,3]
order 120
Expanded truncated icosahedron
etI		 60 (3.4.5.4)
120 (3.4.6.4)		 180 360 182 60 90 12 20       Ih, [5,3]
order 120
Snub rectified truncated icosahedron
stI		 60 (3.3.3.3.5)
120 (3.3.3.3.6)		 180 450 272 240   12 20       I, [5,3]+
order 60

Coplanar misses
Further information: Deltahedron ยง Non-strictly convex cases

Some failed Johnson solid candidates have coplanar faces. These polyhedra can be perturbed to become convex with faces that are arbitrarily close to regular polygons. These cases use 4.4.4.4 vertex figures of the square tiling, 3.3.3.3.3.3 vertex figure of the triangular tiling, as well as 60 degree rhombi divided double equilateral triangle faces, or a 60 degree trapezoid as three equilateral triangles. It is possible to take an infinite amount of distinct coplanar misses from sections of the cubic honeycomb (alternatively convex polycubes) or alternated cubic honeycomb, ignoring any obscured faces.

Examples: 3.3.3.3.3.3

4.4.4.4

3.4.6.4:

  • Hexagonal cupola
    (Degenerate)

See also

References
  1. Kaplan, Craig S.; Hart, George W. (2001), "Symmetrohedra: Polyhedra from Symmetric Placement of Regular Polygons", Bridges: Mathematical Connections in Art, Music and Science (PDF).
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.