There's a new report out that gets into the purported nitty-gritty of Christopher Nolan's new flick -- and in it, Florence and the lead star, Cillian Murphy, are said to be getting hot and heavy pretty often on-camera... in a way CN's never quite attempted before in his work.

Here's how the Guardian describes it ... "Although Nolan is usually, shall we say, antiseptic in his approach to romance, Oppenheimer represents a significant shift." They add, "It features prolonged full nudity for Murphy and Florence Pugh, who plays Oppenheimer’s ex-fiancee, as well as sex, and there are complicated scenes with Emily Blunt, who plays his wife, 'that were pretty heavy.'" In other words, it sounds like we're gonna be seeing a lot of skin.

Welp, that's definitely not something Florence has any problem with ... as she just recently proved at a fashion show in France this past week, where she was rockin' a sheer gown.

More importantly, FP wasn't wearing a bra or anything underneath -- so her breasts were exposed ... and she wasn't shy about it one bit! Of course, her outfit turned heads.

We've actually seen Florence wear something like this in the past -- namely, about a year ago when was at yet another Valentino fashion show in Europe. There, too, she was sporting a braless, sheer look ... and just like here, she was flaunting her body without reservation.

Florence actually blasted trolls who made fun of her for that, calling them out for body-shaming. Considering what she wore this year -- not to mention the forthcoming "Oppenheimer" scenes -- it's safe to say FP is comfortable in her own skin and then some.

Speaking of "Oppenheimer" ... it's finally getting a last push of interesting press in the final sprint before it comes out -- this after "Barbie" has virtually eaten all the attention thus far.