The creation of the shells will be, by far, the most time consuming portion of the build, and frankly it isn’t all that fun. Even with the aid of the Pepakura you are going to be in for long days of sanding and dust. For my build, I sought the help of Pepakura artist DungBeetle, who was gracious enough to allow me to use his pep file for this project. If I had to do it all over again, I'd probably work from scratch, but that isn't due in fault to his work but rather my inability to glue paper together correctly and have it keep an even shape.

While putting together this Instructable, I found DungBeetle's Pepakura files are no longer available to the public, so I have made own using 3DStudio Max and Pepakura Designer, the process of which I have documented below in hopes that it can serve as a mini Pepakura tutorial. If you wish, you may skip this section and downloaded the unfolded Portal Pepakura below or on my website. (PortalShells1-1.pdo, portal shells.pdf)

The first step to creating your own Pepakura file is to rip the model from the game and import it into your 3D editing program of choice. Since there are several major game engines, and many different 3D programs on the market; the tools and techniques required to rip and import the models are going to vary engine to engine, 3D program to 3D program. Fortunately there are online communities that focus on this kind of work, and many tutorials on this subject. For the purpose of this Instructable, I am using 3DStudio Max, and the process for ripping and importing Source Engine models can be found here.

Isolating the Shells:

Once you have your model imported into your software, you are going to want to isolate the areas you want to convert into Pepakura, in this case the Portal gun shells. In 3DSM you can select both shells by clicking on them while holding "crtl", then go to "Edit > Select Inverse" and finally hitting the delete key to remove everything but the shells. Alternatively you can delete parts individually. (pic 1 - 4)

Once the shells are isolated, export your model as an .obj or .stl then open that in Pepakura Designer.

Converting the Model to Pepakura:

Pepakura Designer is a nifty little program that can convert 3D models into 2D patterns that can be printed and cut out, folded, and glued together to recreate a paper version of the 3D model. With the 3D model loaded up in Pepakura Designer, you can hit the unfold button and the program will automatically calculate the folds and open edges for you, but for better results you may want to first identify open edges yourself. Open edges indicate where the paper is cut VS where it folds. (pic 5)

Using the Open Edge tool (select the yellow handled box cutter icon), begin marking the inside edges of the shells. I will not be using the inside curve included with shells, so using the tool to mark cut lines now will allow us to remove those parts we don't want before printing. (pic 6)

Identify any areas that interrupt the flow of main shapes, such as the three bumps around the front edge of the rear shell, and use the Open Edge tool to cut around them. (pic 7)

Use the Open Edge tool to slice the model in the direction that appears most efficient to unfold. Since the shells have a curvy, roundish shape, imagine pealing a banana, or flattening a globe. (pic 8)

Once we have identified all of our open edges, it's time to unfold our model. First, go to "File > Print & Paper Settings" to select your paper size, then uncheck "Auto" next to the Unfold button. Press the Unfold button. If you have unchecked Auto, you will get a pop up dialog with options for sizing. This is where we will scale the model to match our blueprints. According to my scaling, the total width of both shells, including the spacing between them, is 19.6", or 497mm. Enter the value into the correct box and hit OK. (pic 9)

Pepakura Designer will do its thing and unfold the model for you. It is here where we will see how our work with the Open Edge tool has nicely fanned out the parts for us. Had we not used this tool, the pattern would appear far more random. If you like, you can right click on the 2D window and select "Check Corresponding Face" (ctrl+k) and select patterns to see how they correspond with each other and their placement on the 3D model. (pic 10)

As mentioned earlier, the inside curved shapes will not be required, so at this point I have dragged them off the page to get them out of the way. (pic 11)

Right click again on the 2D window to see a drop down menu of your available tools. Along with the "Check Corresponding Face" tool, we also have a Move tool, Rotate tool, and Join/Disjoin tool. Move and Rotate should be self explanatory, use them to position your patterns so that they fit within the bounding box and do not overlap other patterns, but when a shape is too large to fit no matter the position and angle, it's time to use the Join/Disjoin tool. Right click and select the Join/Disjoin tool (ctrl+N) and start selecting lines that run down the center of the large pieces. The Join/Disjoin tool is not unlike the Open Edge tool, it will split your edges apart or join them back together. By splitting down the middle of the front shell, we can then divide it in half and print each half on its own sheet of paper. (pic 12)

Once we have optimized our patterns, they should all fit within the specified paper size and without overlap. (pic 13)

There you have it. Print on heavy card stock and assemble! (pic 14)

If you need a crash course in assembling Pepakura I would recommend checking out this Instructable.



Software:

3D Program (3D Studio Max)

Pepakura Designer

Materials:

Cardstock

Glue

Hardware:

Scissors

Hobby Knife

Straight Edge