> On 27 Apr 2026, at 06.40, wanderer via Origami
> <[email protected]> wrote:
>
> ... folded couple models that were the kind where one precreases precreases
> precreases and then collapses to the finished model.
> ... it’d be really nice to have a name for such models.
That reminds me of a joke by Robert Lang about some of his models: "They are
really easy. Only three steps: Precrease, collapse, shape" (then presents
diagrams with dozens or hundreds of steps...).
I have speculated the same about the need for calling them something. I think I
have seen them called simply precrease-collapse models.
I have called the opposite for progressive models: models where every fold
progresses towards the result.
More precisely, the terminology relates to the folding sequence rather than the
model: models have both precrease-collapse and progressive folding sequences.
A simple example is the preliminary base (or square base).
Precrease-collapse folding sequence:
1. Fold the diagonals from one side.
2. Fold the medians from the other side.
3. Collapse so the corners meet (for the triangle base: Collapse so the sides
meet).
Progressive folding sequence (used in Harbin's books):
1. Fold in half diagonally.
2. Fold point to point.
3. Open one flap and squash fold.
4. Turn over, open the other flap and squash fold.
Hybrids are common. E.g. for the preliminary base:
1. Fold in half diagonally (progressive).
2. Mark angle bisector of one flap (precrease).
3. Open the flap and squash using existing crease lines (collapse).
4. Turn over and repeat steps 2-3 with the other flap.
For the square base the precrease-collapse folding sequence seems more precise.
I am not convinced that is always the case as they also require a high,
technical precision. With progressive models you can compensate for paper
thickness and for inaccuracies in paper and folding as you progress through the
folding. Doing that with precrease-collapse can be daunting and inaccurate.
For the square base I usually precrease-collapse, also when teaching beginners.
Squash folds varies. For dove tails squashes are easier in the progressive way:
Just press it down on each side of the body. The same in the lily base via the
square base: just progressively squash the flaps. However, when folding the
lily base via the triangle base, the flap hides the land mark for the squash,
and so precreasing might be easier.
For the inside reverse folds of the petal fold (e.g., for the flapping bird),
most of the time I fold them directly, but when teaching I always mark the
precreases first.
Which reminds me: You might also consider calling progressive sequences for
direct folding sequences.
Hope this is useful in clarifying the concepts.
Best regards,
Hans
