A few caveats beforehand: While the methods I employ here were able to furnish me with a finished helmet, I am in no way saying these are absolutes! In the end, the best processes to follow are those which you are most comfortable working with, so if there is something here that seems easier to do in your own way, by all means feel free to modify the process to your preferred flavor of building.
I should also note that this is a complicated and lengthy process. The final result took me a little over 4 months to realize, so anyone looking to follow a similar path, be prepared to be in it for the long haul! That said, this is only my second helmet project. If you're more familiar with electronics, casting, moldmaking, or just plain have more freetime than me, your results may vary. This project encompasses elements of sculpting, mold making, casting, soldering, electronic design, and lots of good-old-fashioned sanding.
I am entering this Instructable in the 4th Epilog Challenge because, as you will see, having a laser cutter for some steps in this process would greatly improve the productivity speed! I am an amateur propmaker by trade and, more recently, profession - having a laser cutter to expand the capabilities of my studio would allow for a whole wealth of new opportunities.
Step 1: Blueprinting and Scaling
Before I begin any project, I spend a lot of time scouring online for reference images. The gents from Daft Punk are a fairly elusive couple, and to add to the complexity of sourcing references, there have been a multitude of changes to their helmets over the course of their career.
I try to find as many images from profile and portrait views as possible before beginning my blueprints. These illustrations form the basis of my projects, and are designed in Adobe Illustrator. Dimensions such as the overhead view can be extrapolated from two other viewpoints. (pic 1 & 2)
In the end, the blueprints I designed are an amalgamation of many of the changes to Thomas' helmet over the course of its evolution. Whether you decide to adhere strictly to the subject material or base your designs off of personal interpretation, reference blueprints are essential! These will keep you on track and make sure all elements of your project stay consistent and accurate during the course of your build.
In order to scale these blueprints correctly, I open the blueprints in Illustrator, then import a picture of the wearer's head next to a ruler. After scaling the picture appropriately to the ruler's marked dimensions so that the scale of the person's head is 1:1, the blueprints are scaled and printed accordingly. (pic 4)
While this may not be the most precise measurement, I find that it works fairly well with some practice. Often times you may have to take into account lens distortion or other factors depending on how the reference image was shot.
When printing a blueprint, I usually print three copies: one at 105%, one at 100% and one at 95% - these are all compared when printed fullscale to see which one has the best "feel" as a full image. Sometimes seeing the print just slightly larger or smaller can help determine what looks best.
A while ago my Dad rescued a roll-fed plotter from the dumpster of a local school and it now lives as my blueprinting machine. If this isn't an option, you can either try a local print shop, or scale your blueprints with registration marks to fit on normal sized paper. (pic 5)