The additive 3D printer (hereafter called Add-3D) creates a 3D object with materials being added together layer by layer. Before printing an object, some professional processes are indispensable, such as creating the 3D printable models by computer-aided design (CAD), or 3D scanner, and STL data modification, which are difficult for normal families. As we know, primordially, origami is the ancient art of folding a flat-piece of paper into a 3D shape, that even can be played by kids. So we aim to develop an Origami 3D printer (hereafter called Ori-3D) that can be used by ordinary families with the features of effort and no size limit of model. In Ori-3D, the object is constructed by human hands or by an Origami robot using 2D patterns generated from 3D data (obtained from photos or CAD). Ori-3D includes the following steps: 1) the surface of an object is segmented to several developable surfaces as large as possible using segmentation technique which is used in reverse engineering system. 2) Each developable surface is developed to 2D pattern with mountain & valley lines and glue parts. 3) The 2D crease pattern is optimized by a tree structure method to be easily folded by an Origami Robot. 4) With Origami robot, the object is easily constructed from the improved 2D crease pattern. This paper focuses on discuss the steps 1~ 3: generation of the 2D crease pattern.