Crease pattern


Post is a part of a larger series (Design process):

Nowadays, the vast majority of origami instructions are available only in the form of a crease pattern. Diagrams have become increasingly rare, even though they still can be found in magazines like Tanteidan or Origami books. But since the production of new models is so immense in most cases only what is available are crease patterns. 

This is for some reasons perceived as a problem. And for the same reason, people are intimidated by crease patterns. They do not know how to read them properly and what is most important they do not know how to collapse them. In such situations, frustration is common but It doesn’t have to be. Reading crease patterns is in most cases straightforward task.

Types of crease patterns

Models based on the Circle packing method or technique and models based on Box pleating technique have distinctly different crease patterns. In figure 1 you can see two typical crease patterns.

Crease patterns
Figure 1

I believe that nobody should have difficulty recognizing underlying techniques. The first crease pattern is based on the Circle packing techniques, while the other one is based on Box pleating technique. How do we know that? 

If you look closer, you will notice that the crease pattern based on the Circle packing technique consists of mostly radial creases. On the other hand, the Box-pleated crease pattern consists primarily of parallel and perpendicular creases.

Nevertheless, no matter which technique is used, both share a few common features.

Flat-foldability rules and disappearing creases

Origami crease patterns are heavily influenced by flat-foldability rules. Meaning, the crease pattern does not show all the creases, but only these that are visible when the base is fully flattened. In flattened form, large numbers of hinge creases are not visible. They are simply not shown. That could be a problem for origami newbies because they will sometimes have trouble recognising the polygons.

A more in-depth explanation of this phenomenon can be found in my blog post about Hinge creases. Even though examples in that blog post are based on the box pleating technique, the principle is applicable to both types of crease patterns.

For instance, in figure 2 both crease patterns are shown but this time with clearly marketed polygons.

Crease patterns with polygons
Figure 2

As you probably know, the border of the polygon is nothing but the hinge crease. And if you properly examine both of these crease patterns you will certainly realize that many polygon borders are marked by auxiliary lines. Meaning, they do not exist in a flat-foldable form.

Crease pattern represents a base

Another very important aspect of crease patterns is that it is a blueprint of a base not of a model itself. Remember that: a crease pattern hardly ever represents a complete model. It usually represents only the base of a model. 

I will give you a very simple example, a traditional crane. 

Traditional Origami Crane
Figure 3

In figure 3, you can see the crease pattern of a traditional crane and its base. The first crease pattern depicts all courses needed to fold the crane, meaning the crease pattern represents the full model. The second one shows only the base. As you can see, the crease pattern of the base is much cleaner and therefore much easier to read and fold. Of course, few additional steps are needed to fold a final model, but in most cases, it can be done easily. On the other hand, the crease pattern that shows the full model is cluttered with creases. Consequently, it requires additional analyses to recognise the base itself. Adding all these additional creases to the crease pattern can introduce substantial noize which must be cleared. That is true for complex as well as for simple models.

In the case of a traditional origami crane, the distinction between the base and the final model is obvious, simply because the traditional crane is based on the bird base, which can be easily recognised. On the other hand, the distinction between the base and the final model for more complex models is not always clear. So, many authors decide to provide crease patterns that show only the base. After all,  the bases designed using a circle packing or a box pleating technique are the ones that hold the secrets of a new model. Once you fold the base it is most often very easy to fold a model itself.

Collapsing

Finally, when someone mentions a crease pattern, probably the most frequently asked question of all is always about collapsing. Collapsing is not as hard as it seems. Nevertheless, there are some differences in the collapsing procedure between models based on a circle packing technique and a box plating technique. It is out of the scope of this blog post to explain the collapsing procedure in detail. After all, for box pleated bases you can find an extended explanation in the blog post How to Collapse Box Pleated Crease Pattern? But before you dive into the procedure explained there, I strongly encourage you to become more familiar with the types of creases used in box pleated crease patterns. Namely,  Hinge crease, Ridge crease, and Axial crease.

Collapsing the crease pattern based on the Circle pattern technique is somewhat different. I will try to explain the basic procedure using a fairly simple example.

Circle packing technique
Figure 4

According to the general procedure, first, we have to analyze the structure of the base. Meaning, we have to know how many flaps and rivers are there. Then we have to find all the creases that connect the circle centers. Look at figure 4. All these creases are marked in purple and are called Axial creases. They will coincide with one another, once the crease pattern is fully collapsed. Quite interesting, isn’t it? 

These lines define polygons, naturally called axial polygons. They can be of different shapes, but in most cases, they are rectangular or quadrangular. In our simple example, all axal polygons are rectangular. Crease pattern inside the axial polygons is most often a simple one. But, it could be more complex, if some type of flap narrowing is introduced. Since our example is a simple one, inside every single axial polygon, we have a distinct pattern known as “rabbit ear”. 

Now we come to the fun part, the collapsing itself. As in the box plating technique, here too, we have to collapse the central polygon first. Look at figure 5

Collapsing
Figure 5

When the central flap is collapsed, what is left is to create additional edge flaps according to the crease pattern and that’s it. Easy isn’t it. Of course, this example is very simple but the procedure is applicable to the most complex crease patterns as well. I will most definitely write a longer blog post dedicated to the collapsing procedure of crease patterns based on the circle packing technique. There I will explain the procedure in detail.

Conclusion

Crease patterns can give more insight into the design process than diagrams because diagrams tend to obscure the underlying structure of the model. I understand that diagrams are more convenient, especially for newbies, but crease patterns are far more valuable. Anybody who aspires to origami mastery should make an effort and learn to read and collapse crease patterns properly. It is not always easy, but I can assure you that it is not that hard either.