Despite the downbeat nature of Sigourney Weaver’s new film, “A Map of the World,” in which her character ultimately ends up in jail on charges of child molestation, the star was all smiles at a New York cocktail party before the screening Thursday night. She was even upbeat when asked about her nude appearance in the movie. Weaver said she was comfortable doing the scenes with costar David Straithairn (who plays her husband) because they depicted real-life situations. “We’re naked,” she told PEOPLE, “but I wouldn’t call them nude scenes. We’re getting in and out of bed. Big deal,” she said, her voice rising an octave.