PAPER

A new crease pattern will automatically set itself to be a unit square

var cp = new CreasePattern().square()

There are a few popular shapes you can set by name, like rectangle

var cp = new CreasePattern().rectangle(1.618, 1)

Any polygon can be made by supplying an array of points (convex & clockwise winding).

var pointArray = [
 new XY(0.5, 0.5),
 new XY(0.0, 1.0),
 new XY(1.0, 1.0) ];
var cp = new CreasePattern().polygon(pointArray)

Origami

It's fun to try to fit origami crease patterns onto non-square paper