Making things out of paper is a lot of fun. However, many of the instructables and other instructions around the web reccomend Pepkura for converting a 3D model into a template. While I have nothing against a paid software product, it is nice to know that it can be done just as well with an open source solution: Blender3D.
Blender3D is the 3D modelling tool in the open source world. It get's used for a huge number of things, and there is a great community around it who continously extend and develop it. In particular, one community member made a plugin called "Export Paper Model"
Step 1: Setting Up Blender
First things first is to get your tools set up. So download blender from the blender website. I did this instructable with 2.77a, the latest version as of the time of publishing. Now you need the paper extension. So download it from this link. You will probably have to right-click "Save File As" otherwise it will just open in your browser.
Now we have to install the extension on blender, so open blender and click:
- File-> user preferences
- Go to the addons tab annd click the button in the bottom corner: "Install from file"
- Select the extension file (should be called io_export_paper_model.py) and click "Install from file"
- Enable the addon by clicking the checkbox next to it's name
Check that it has installed by seeing if there is an entry "Paper Model (.svg)" under export. If it isn't there you probably didn't click the checkbox to enable it.
Every new blend you make you'll need to re-enable the paper model export addon. Not reinstall it, just click the tick next to it's name.
Step 2: A Trivial Example (Paper Cube)
First, let's check it's working by exporting the default cube.
- Select the cube with right mouse button (blender is a right-click interface)
- File->Export->Paper Model
- Set the scale to 1:100 (see image)
- Give it a name and export it
Voiala, we have a paper cutout for a cube. It's automatically put in tabs and numbered them. The scale of 1:100 made it smaller so it fits in the corner of the page. With a scale of 100, a cube 2 blender units wide will be 2cm wide.
If you get an error about the island not fitting on the page (last image), check that you set the scale to 1:100
A quick overview of blender's interface
Blender is a bit of a behemoth. It can do a huge amount more than I am explaining in this instructable. Here are the user interactions that tend to be the most useful. I'll explain these when needed as well, so don't be too concerned.
- Middle Mouse button to rotate the view
- Shift + middle mouse button to pan the view
- Scroll wheel to zoom
- Right Click to select
- Left Click to intereact with the UI (eg draggable handles on selected objects)
- Space and type to execute a command (if you don't want to look for the button)
- Tab key to toggle mesh edit mode
Step 3: Trivial Example 2: Seams
That cube template is a little weird isn't it? A more typical shape is the cross shape. So how can we get it to do that? We use ... seams!
- Go into edit mode using the button at the bottom of the 3D view (or press the tab key)
- Put the selection type into "edge" mode
- Select the edges you want to turn into seams with right-mouse button (use shift to select multiple)
- On the sidebar click "Shading/UV's" and then "Mark Seam" (or press space and type "Mark Seam")
- The seams should be marked in red.
- Exit edit mode (switch to object mode or press tab key) and export the model again.
If the sidebar isn't visible, try pressing "T" on the keyboard.
Wouldn't it be great if we could preview the seams? Well, we can.
- Change one of the windows to UV editor
- Go into edit mode and press the "a" key to select all
- Go to the Paper Model tab and press "Unfold"
- Ensure the "Create UV Map" is ticked.
Now a preview can be seen in the UV editor.
Step 4: A Deer Head Example
This seems to be the standard 3D papercraft demo here on instrutables doesn't it? So I'll join in.
- Download the stl from thingiverse. (Thanks Takeshi for providing this under CC-BY-SA license)
- Import it into blender using file->import->stl
- Scale the model down to a managable size by pressing "S" key and typing 0.01 followed by enter.
- Add a decimate modifier and set it to "0.003" See the image for how to do this.
- Apply the modifier using the apply button on the modifier.
The deer head 3D model is very highly detailed, and your computer may run slowly. On my (mid-gaming-spec) computer the decimate modifier took several seconds to update. Now go through the process of adding seams and unfold the mesh as per the previous two steps. You don't have to mark all the seams, the unfold is slightly intelligent.
I have attached the final blend file.
- Does it fit on the page? Try changing the scale
- Is there any malformed geometry (faces that overlap/intersect etc)? Remove them by merging vertices (M key), moving them (G key). Look up how to use blender for mesh manipulation for more detail.
Step 5: Textured Space Ship Example
The first model I did this for was the player space ship from the 1995 game Descent. The model came from the game and was extracted by some member of the community. I can't find where the original came from, it's been sitting on my hard drive for several years now.
This time we want to preserve the textures into our paper model. Once again I've uploaded the blend file so you can see where I placed the seams. Because this is a lot simpler model than the deer head, the seams were placed manually to make the printouts easy to fold.
- First off I needed to clean up the model for paper-craft. This included making sure there were no overlapping faces. (Of which there were a few).
- Then I textured it, as when I got it it was just polygon data, so the textures were made in Gimp.
Making the Paper Model
The only difference here is that we need to use multiple UV layers. One for the color, and another to preview the unfold. That involves making sure the texture sheet in the material use the correct UV map. I don't particularly feel like explaining how to use blender's material system so I'll point you at this tutorial.
Then it's just a case of using the 'From Materials' option in the paper exporter.
Step 6: Where to From Here?
Well, there is a whole world. You could talk about the journey from concept art to 3D model, you could look at baking the details on a high resolution model into a low resolution one. I may well make some more tutorials at some point, as doing papercraft is really fun, especially if you're the person who made the pattern.
I'd also like to investigate slicing for papercraft in blender, so that shapes can be built up from layers, but (to my knowledge) no-one has made an addon for that yet.
Well, have fun and go make stuff!