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| | Origami & Catastrophe Theory (Site not responding. Last check: 2007-10-08) |
 | | In flat folding, the folds of a model and the model itself are collapsible onto a flat surface. |
 | | In the case of the crimp fold, the fold lines and the surface or surfaces formed by the fold may be curved. |
 | | The second catastrophe geometry, the Cusp manifold, is the equivalent, in flat folding, of the reverse fold; third, the Swallowtail manifold, is the equivalent of the double reverse fold; and fourth, the Butterfly manifold, the triangular sink fold. |
| www.paperfolding.com /chengchit/3d.php (448 words) |
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