The lovely thing about basing a project off of a video game is that a designer somewhere has gone through the immense trouble of making a beautiful 3D model for you to work from. If the game you're basing your project on happens to be available for PC, then chances are there is a modding community out there that has extracted these files and can help source some perspective still images or even the 3D model itself. (Pic 2)
For this project I'll be building the female "Ancient Nord Helmet" (also called the female Draugr helmet) from Skyrim. The models for this helmet were provided to me by a gent who mods these games, and I used the perspective screenshots in order to make 2D blueprints of the top, sides, bottom, and front/back of the helmet. (Pic 3)
There is a rather large community of costumers who also employ a method called Pepakura
(essentially complex paper folding and cutting) in order to achieve very similar results using game files as a base. While this is an excellent method, I personally suck at it, hence this Instructable!
One of the questions I have received the most concerns how to scale blueprints. Recently I've found a great method for this: Print off a 1" grid onto a sheet of plotter paper, then trim out a space for your subject to stand. Photograph this as close to perpendicular as possible, then import the photograph into an image editor such as Adobe Illustrator. By scaling the image so that the 1" squares are indeed 1" in size, you can then import your blueprints over the image and find all the dimensions of your finished part! (Pic 4)
Once your blueprints are scaled, print them at full scale on a plotter. A local print shop can assist here if you don't have access to one of your own.