Hyphens, En Dashes, Em Dashes

Q. Do I not have the hyphenation correct in phrases like “3-D printing” and “2-D projection”? I figure that they feature an abbreviation of the word dimensional being used as an attributive compound adjective, so they do call for hyphenation. I ask because one often encounters the abbreviations styled as 3D and 2D. Am I being overly fussy?

A. Yes! Fussy! Chicago style is 3-D (or three-dimensional), but other style guides and dictionaries are fine with 3D. See, for instance, American Heritage Dictionary, which lists 3D first.