Interesting they use a Star Wars example. There was a major copyright case on my side of the pond - in the UK - in 2011 about whether a Star Wars stormtrooper helmet was a sculpture, covered by copyright, or just a movie prop (so covered only be industrial design rights, which unlike copyright only last 10-15 years).

It was held not to be a sculpture. So if you're in the UK, you can 3D-print stormtrooper armour without worrying about being sued by Lucasfilm.

The court didn't give a concise definition of 'sculpture' - they listed some relevant factors, but mostly left it to the common sense of the trial judge. Quote: "it is inappropriate to stray too far from what would normally be regarded as sculpture. ... Not every three dimensional representation of a concept qualifies".

http://www.supremecourt.gov.uk/decided-cases/docs/UKSC_2010_...

(Emphasis: this is under UK law, not US. I think the opposite result was reached in the US, but don't quote me on that. IANAL).