「Not foldable tiling in two-toned」
foldable tilings
A not foldable (crystallographic) tiling over the plane:
>>Click the image to see the larger picture<<
The significance of the example above is:
the diagram consists of foldable structures around each vertex [namely, it is generated by 'locally' foldable structures], but it is not composed into foldable tiling as a whole.
In fact, it is satisfied [necessary and sufficient] flatly foldable conditions at each vertex represented in the angular relations [given by T. Kawasaki in his papers up to general cases of geometry] as follows:
π/3 + π/2 + 2π/3 + π/2 = 2π (rad) [60°+ 90°+ 120°+ 90°= 360°];
π/3 - π/2 + 2π/3 - π/2 = 0 (rad)
__[60°- 90°+ 120°- 90°= 0°].
On the other hand, it is not flatly foldable because of the combinatorial folding conditions with respect to the relations between mountain-/valley- creases and values of angles. [Try to fold it: then you will realize it is not foldable.]
Around 1993, the author found a monotone drawing of that tiling - like
this - in the figures on Archimedean solids and
semiregular tessellations, those appeared in the Japanese translation of the book by L. Fejes Toth:
"Lagerungen in der Ebene auf der Kugel und im Raum" (2nd ed.), Springer, Berlin, 1972 - although there was no discussion about 'foldability' of such (planar) tilings/tessellations -.
[And he informed several paper-folding artists about this diagram and the book: within his remembrance...]

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