Methodology for creating 3 D paper unfolded models with complex geometry using open-source software and resources with free personal and commercial license

The creation of 3D paper unfolded models with complex geometry requires precision in the design process. Achieving this is through the use of accessible resources and modern technological means which possess the necessary technical and functional capabilities. The successful realization of the models is through the use of a structured methodology containing design stages that are defined in the exact sequence. The present study aims to create the unfoldings of complex three-dimensional models by covering the stages of providing accessible resurses with a personal and commercial license that are transformed in sequence until the readymade variants.

1 Introduction software, i-link visited 2018, Dovramadjiev T., 2015, Wickes, 2009;Prahov, 2009), their specific functional qualities and the right approach for the production of unfoldings of three-dimensional models for making them from paper.

Materials and Methods
Given the many features accompanying the development of unfoldings of 3D models with complex geometry, the construction of an optimal methodology is a necessity.
In Fig. 1, there is shown a method for creating a three-dimensional pattern unfolding comprising the following steps: 1. Providing vector and / or raster resource of symbols, letters, ornaments, figures of people, animals, buildings, vehicles, etc.. 3. Importing the svg (Scalable Vector Graphics) file into a Blender environment (open-sourse software running on polygonal mesh models).
4. Extrusion of the vector into a volumetric body.
5. Using Boolean operations to create (cast) the finished 3D model.
6. Automated creation of unfolds.The efficient use of the methodology is applied in the development of an exemplary vector model -an ornament that is provided through http://www.fontspace.com/.The resource has a free and personal and commercial license (Fig. 2).Scalable Vector Graphics file-ornament is imported into Blender software via "File"> "Import" (Fig. 4).The resulting object is rotated, positioned and extruded at 0.15m (Fig. 5)  Using Add> Mesh> Cube, a new 3D object is created -primitive cube.It is transformed and positioned in the middle area of the casting mold (Fig. 6).The two objects are sequentially selected for the imported object and the "cube" and the Boolean operation is performed Brush Boolean / Difference (Fig. 7; Bool Tool Addon -Author(s) Vitor Balbio, Mikhail Rachinskiy, Tynka Topi, Meta-Androcto).Upon receipt of the form, it goes to the construction of the polygonal mesh through the Object > Convert to (Alt C) > Mesh from Curve/Meta/Surf/Text (Fig. 8).

Results
Using the Blender Addon: Export Paper Model, the unfolding of the model-ornament is automatically made.The result is shown in Fig. 9 (a).In Fig. 9 (b) and (c) there are other complex models shown that are made using the same methodology.

Conclusion
In the present study, a model of a three-dimensional polygon mesh object was made using a newly developed methodology, providing the necessary conditions for successful realization.The here shown results of the made unfolds and other models with complex geometry characterize the defined technological path as a fully functional.Based on this, as well as the availability of the free license and open-source technology tools, it is concluded that the constructed methodology provides suitable conditions for the realization of paper models by automating the process.This leads to an increase in the accuracy and quality of the obtained models.
2. Creating a vector footprint (negative image of the image) by tracing the image in the Inkscapeopen-source special software.

Fig. 2 .
Fig. 2. Providng the resource ("P" key).WWFloral Corner font.Licensed as: Freeware Personal Use & Commercial Use.http://www.fontspace.com/windwalker64/wwfloralcorner.The font "WWFloralCorner.ttf"(WWFloralCorner font) is installed in the "Fonts" folder of OS Windows and opens in the open-source Inkscape.A white background needed to create the print is added to the vector ornament.The model is captured in an image.Creating a vector footprint of the resulting image using Path> Trace Bitmap (Shift + Alt + B).In the "Trace Bitmap" window is marked "Invert image", and it is desirable to use "Live Preview" (Fig3).

Fig. 6 .
Fig. 6. Preparation for casting of the form in a computer environment.

Fig. 7 .
Fig. 7.The resulting shape of the pattern -ornament following a Boolean operation.

Fig. 8 .
Fig. 8.The resulting ready three-dimensional pattern -ornament.In Edit Mode, the model's mesh structure is polygonally displayed.