On 8/4/13, KDianne Stephens <[email protected]> wrote: > Why does Origami diagramming use a different arrow to indicate a mountain > fold when the drawn line indicates to do a mountain fold?
In his (most excellent) article on diagramming, Robert Lang writes: "An arrow associated with a mountain fold has a single-sided hollow head (figures 9 and 10 show examples). It should be used whenever the paper is folded away from the reader, and to emphasize this motion, the arrowhead should hook behind the moving flap if that is the appropriate motion of the paper. As with the valley fold, hooking the arrow around layers can eliminate ambiguities about what goes where." (http://langorigami.com/diagramming/diagramming.php) This is builds on the concepts he describes surrounding the logic of needing an arrow at all in diagramming a valley fold: "But putting in a dashed line for the valley fold is only half the story in conveying the fold. The other half is the arrow. The arrow's importance in communicating a model to the reader cannot be underestimated. This is especially true in drawings for the beginner. Beginners approach folding from diagrams differently from those more experienced in the art. The experienced folder will look at a figure with a dashed line through it and think "Ah, I must make a crease that runs from point A to point B." That is, an experienced folder will think in terms of where the crease must go. Very few beginners approach folding that way. Rather than concentrating on where the crease is to be placed, a beginner wants to bring one point to another and let the crease fall where it may. In this approach, the actual location of the crease is not very important. Therefore, you must show an arrow that indicates clearly the motion that the paper undergoes." (Lang, ibid) When teaching, I too have found this to be a really noticeable difference between beginners and more experienced folders - their perception of what you're "doing" when you're making a fold: beginners perceive the motion and details of the alignment of the flap/layer/corner/edge they're manipulating, while more experienced folders see the *crease* they're forming. (When you teach different level audiences, you very much have to take this difference in perception into account, or the students have no idea what you're talking about... I always talk about this when I teach, and love the little lightbulb moments when someone suddenly sees the crease, and not just the flap!) So, seems to me that if everyone who would be reading your diagrams were of sufficient experience, there'd really be no need for the arrows - but having them, and having different ones for different motions of the paper helps to make the diagrams more easily and widely understandable. Anne
