Updated 10 Aug 2003

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Paper Model Design

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This tutorial is the first one on this website aimed squarely at using Rhino for designing parts for paper models. Rhino is very capable 3D modelling tool.  The limits of making a model from a sheet material which can only be folded or bent in one direction put some constraints on what we can create, but the power of Rhino will save a great deal of time with many model design problems. The files used can be downloaded here so you can work along. This tutorial has been written using Rhino version 2, and assumes a working knowledge of the software. If you need additional help with the various commands, snap functions, creating curves and surfaces, check out the help files and tutorials that ship with Rhino, or ask us by e-mail. We are always pleased to help if we can!

In all these examples, Rhino is used to generate lines which are then exported to a 2D graphics program for further ‘tweaking’ and colouring. We are using CorelDraw v9, but Illustrator or many other vector drawing programs will work just as well. Rhino can export data in a variety of formats, in this case we will use the .ai (Adobe Illustrator) format, which imports into CorelDraw very well. You may need to try several different formats to get the best result for other software packages. You can also import vector data into several Paint packages such as Photoshop or Paint Shop Pro. This is very useful if you prefer to use a bitmap ‘paint’ program rather than a vector package.

1.     Rhino models 3D objects with curves, surfaces and solids (which are just a set of surfaces which fully enclose a volume with no leaks). Our physical model will be made from pieces of paper and card printed out on our computer printer. We can keep our paper parts flat, or crease them to form a sharp corner, or ‘roll’ them to produce a tubular form. What we cannot do is form a compound curved surface, so our virtual model will have to be designed within this limitation. There are programs which will ‘unfold’ a mesh model to form a flat pattern, and we will look at some of these in a future tutorial.

2.     If our model is constructed of flat surfaces we can easily extract or explode surfaces from our 3D model. Each piece can then be rotated in 3D so it is flat in one view, selected and exported as an .ai file. Here is a simple model of a house. This was made by extruding the end wall, adding the chimney as a  small black and doing a boolean addition. Then using some more blocks and the trim command to cut out the door and window openings. Finally the whole model was ‘exploded‘ so each face is a seperate surface. In this first picture, you can see the front wall with the windows has been selected and is in yellow.

3.   We can then rotate this wall in 3D along its corner with the end wall, unfolding it just as we could do with a real paper model. Each wall can be manipulated using the standard Rhino snap and move functions until we have all the parts laid out in one plane. In this view we can see the last wall being rotated in 3D about corner A-B so that all 4 walls are in one plane.

3.     Working through the model face by face, the whole structure can be opened out to form a flat design. Smaller parts can be seperated and opened out individually. The chimney has been treated this way here.

4.   Changing to a view straight on to the opened out model, select the walls, roof and chimney parts and ‘export selected...’ as an Adobe Illustrator (.ai) file, saving it somewhere sensible.

5.   There will be a dialogue box asking for the units in which the .ai file should be exported. Select units appropriate for your work and then save the exported file. It can then be imported into your 2D graphics package (CorelDraw, Illustrator, Paint Shop Pro etc.) for colouring, duplication and layout.

6.     The .ai file data will probably require some further work. For example the image may be grouped, the line thickness and colour may need altering and some elements may be duplicated or surplus to requirements, and so need selecting and deleting. In the image above, the isolines crossing through each model face have been removed. Any tabs, text, cut and fold lines can also be added to the image at this stage. The model can then be printed and test-assembled. Adjustments can then easily be made to the graphic data without disturbing the original 3D Rhino model. make a note of what adjustments are needed. These will vary depending on the form, breakdown and size of the model, and particularly with the weight and type of paper you are using, and your notes will be useful in designing future models.

This little house is a very simple model, but the process of opening out a 3D structure into 2D surfaces, then exporting an image of the data to a 2D drawing package is the same for all the following pages of this tutorial. Next, we will look at a more complicated model, and some of Rhino’s very handy surface tools, including Unroll Developable Surface. Click here for the next page.