On 22/07/13 19.20, Meenakshi Mukerji wrote:
Other than the points already discussed I also make a distinction between "turn over
laterally" vs "turn over vertically". The results may be quite different based on
the symmetry of what you are folding. So the arrow head may not always point to the next step.
The purpose of the arrow anyway is not to point to the next step. Please see what I mean here:
http://www.amazon.com/Origami-Inspirations-Meenakshi-Mukerji/dp/1568815840/
Click "Look Inside: and go to page 5.
You are right, and as Gerardo points out, it is also in Lang's paper.
But also note that I would always point the arrow towards the next step.
In the horizontal turnover, it points right because the next step is to
the right, or in the beginning of the next row. However, in the
free-flowing format where the steps flow around on the page (I like
those, looks very elegant though some people say they become confused),
the horizontal turnover points *left* iff the next step is the left
(well, like Anna I can't say I have seen every diagrammer's take on this).
Likewise, I'm sure I would let the vertical turnover arrow normally
point down as this is most close to the normal reading direction, but if
the next step is above the current (some reading cultures have that, and
in free-flowing format it often happens), I would like let it point up;
that is, if I would ever use it. More likely I would stick to the to me
normal one and let people infer intuitively what happened.
Directions are always difficult. Left- and right-handedness come into
play, as does the pop-in pop-out perspective ambiguity.
In your above-mentioned page 5 (nice instructions, by the way), you
write "fold towards yourself" for the valley fold: Interestingly, I
advice origami students to fold *away* from themselves when making a
valley fold, because they usually fold on a flat surface and I find that
provides better control than trying to fold towards yourself. And
describe the mountain fold to mean to turn over the paper, valley fold
away from themselves, and turn back again; this since you physically
cannot make a mountain fold on a hard surface, and folding in the air
(as your instructions linguistically imply) is not precise enough for
most people and folds. But of course I understand your meaning.
In this sense, except for pinch folds, the mountain fold is an
artificial construct living in the diagrams only.
Or for that matter, it is the other way round: place the paper on the
table. Make a valley fold, in any direction, flat. Look at the fold.
What do you see? The *mountain* fold, i.e. the outside of the fold. Only
if you subsequently open up the paper, you can see the otherwise
concealed valley. In this sense all folds are mountain folds... All
this just to show that the terms "mountain" and "valley" folds
themselves are arbitrary labels depending on a specific conception of
the viewpoint. They only become intuitive because you can see for
yourselves the position of the paper in the before and after steps.
This is like the concept of arrows on parking signs along the roads. In
Denmark, a downwards pointing arrow on such a sign means that the
parking instructions are valid on you side of the sign. This because we
perceive the sign lying flat on the ground, as if we ran it over.
However, I have heard that in China (someone confirm or correct me) the
same downwards arrow means that the instructions are valid on the other
side of the sign. This because they perceive the sign as if they look up
on it, as if it was flat on the ceiling.
Best regards and happy diagramming,
Hans
Hans Dybkjær
papirfoldning.dk
