Star Wars: Rogue One - 16 Major Details Lucasfilm Just Revealed
7. They Did Test Shoots On The Force Awakens Set
This one's not all that revealing about the content of Rogue One, but is an interesting tidbit nonetheless that speaks of the extents Gareth Edwards has gone to ensure he accurately captures the original Star Wars aesthetic.
When talking about the first day shooting Darth Vader, the director told a rather surprising story; that was on the set of The Force Awakens in 2014. To get the lighting of Vader's suit right (which, to be fair, is a pretty big deal - it could so easily look like just a guy in a plastic helmet), they did some test shoots on the Starkiller Base set (which visually operates similarly to Star Destroyer bridges and Death Star hallways).
This is probably where some of the rumours about Vader being in Episode VII came from - that's suit is one thing it's pretty hard to miss - although it could also be an allusion to a change made in the development of that film; originally Vader was going to appear in Rey's vision. Perhaps there was even a leftover suit.