The term 3 steps model was originally proposed by Brian Chang, a student at MIT and brilliant origami artist. In his words, the 3 steps are:

*Pre-crease
*Collapse
*Shape

These 3 steps seem simple enough for the average origami enthusiast. However, it must be noted that in the average model that uses this technique, the average time required to perform each step is counted in hours and sometimes in days. This level of complexity, while daunting, is also an important factor when judging an origami design. There are many impressive origami works that acquire their true meaning when it is understood just how much effort the artist put into that single piece of artwork.

For those who do not know, the 3 steps model comes from a new development in the origami design field. Given the new discoveries relating origami to some mathematic fields, mainly graph theory and computational geometry, the use of computers and algorithms as aides in the design of origami models has changed many rules that were believed true for many, many years. These computer aided designs, when translated to the paper, do not turn out to be like traditional origami designs. This is, they do not come out as a sequence of folds to be executed one after the other, but more like a collection of folds that come together in the end. Following is a brief explanation of each of the steps.

In the pre-crease step, instead of just doing one fold after the other, the artist creases the square as a whole, folding and unfolding as necessary. The idea here is to crease each section of the square in a way that aids the collapse stage, where all this folds come together. The main point that separates this from traditional origami is the skill of the origami artist, which allows her to understand, from the very beginning, which part of the square will be used for which part of the model. That is the only way an origami artist can crease the whole square without relying on a sequence of folds.

After all the creasing is done, the artist brings all the folds together into a basic shape in the collapse step. In traditional origami, there are many bases, like the bird base or the water bomb base. From this bases many more models are made just adding further folds. In the 3 steps models, the collapse step creates a model much like the traditional origami bases, just with a different complexity level. At this point the model does not really look a lot like the intended end result, but it has all the features required to shape it into the desired finished model.

The shape step is probably the one that resembles traditional origami the most. In this step, the origami artist, using all of her expertise, gives the final folds that turn that basic shape into a beautiful piece of artwork. Here is also the point where theory and math are thrown away and real art comes into the picture. This is the step that separates origami artists from origami Masters.

In the end, with the help of a computer, anybody can create a model that will have a head, two arms and two legs, but only a real origami artist can turn that into something that resembles a person. And that is also why, no matter how much the new discoveries use math to further develop origami, it is the artistic sense in its constant strive for beauty that turns a piece of paper into a masterpiece.

Reference:

Interview with Robert J. Lang on the topic. http://www.howtoorigamiblog.com/how-to-origami/how-to-insane-origami

Robert J. Lang explains about the applications of this. http://www.howtoorigamiblog.com/how-to-origami/how-to-origami-industrial-revolution