Pepakura is basically papercraft. It’s a model usually made from thick paper such as card stock or foam. Printing pepakura files for helmets and armor is one way to start a build, but it takes a lot of work to transform the material into the finished product. RPF user Cereal Killl3r documented how he did it for his Master Chief cosplay, and it’s simply incredible to watch paper evolve to a smooth piece of armor. I’m floored.
As he continued the Halo 3 build, he started making how-to videos. The first one is about applying fiberglass resin to the pepakura to harden it, and the video is packed with information.
More about the process including a ton of progress photos are over at The RPF. This is one of the most well-documented builds I’ve ever seen.