I think the Warp Core and other parts of the ship were filmed at the National Ignition Laboratory so probably a good part of it was just what was there, but it will have been augmented by visual effects and some additions for the movie I expect.
I liked the design a smidge more second time around. It at least fits into the established look of things.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist