Using a pair of calipers (with a digital screen), stickey-tak (for rough sizing on an example figure), I took accurate measurements (height, usually) using an aproximated base figure to avoid big-head syndrome.
Using a host of other programs, including Google Sketchup 8 (with plugins), Meshlab (to export .stl files), and Netfab (to fix, re-do, and export the .stl for printing), and Shapeways.com - I'm hoping to make game-accurate ~6" scale (think NECA's Colonial Marines / Rambo / Predator: Dutch sized figures) renditions of the NCR Ranger, Power Armors (Brotherhood of Steel + Enclave), as well as the Eyebot.
There's some limitations - both in the tensile strength of 3D printed material from Shapeways - the minamum thickness needs to be just under 1mm (0.8mm) - and lower, and it can't be printed. That resulted in all objects that were wires, tubes, or antennas being deleted. I'll need to replace those with scavenged metal or ABS plastic parts during assembly. Also, some items are just too expensive to print. I haven't figured out how to reliably make an object hollow (and avoiding mesh errors), so for now the Robobrain, and parts of Liberty Prime are just a pipedream.
I've sent the current batch in for printing, so hopefully they turn out.
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October 2013 Update:While the other heads failed to print (due to a .01mm wall thickness issue on some hoses/antenna), the NCR Ranger helmet pieces printed well.
After discovering sanding barrel attachments tend to gum-up when used on Shapeways-printed plastic, I switched to a thick bladed metal dremel tool to smooth out the geometric surface. That, combined with significant sanding created a workable print.
The current version has progressed beyond the image above, as I've added liquid type superglue to the print surface (it soaks in), and sands factory-smooth. Once that's finished, I'll be adding the helmet's side-camera and antenna in preparation for casting.
March 2014 Update:
More progress with the NCR Ranger customs figures here.