Robert Pattinson turned his frown upside down!
After a charming appearance on The Daily Show and a red carpet walk at MOMA, the 26-year-old didn't shrink into the corner for the Cosmopolis premiere afterparty at The Dream Downtown hotel in NYC's Meatpacking district.
Following a private dinner at the hotel's Library, the Gucci-clad actor -- making his first public appearance since news of girlfriend Kristen Stewart's affair broke -- "looked happy," one observer tells Us Weekly.
"He was friendly and spoke to everyone that said hello." One topic that never came up? "There was no talk of Kristen," the observer says. "He was smiling and laughing a lot."
Arriving at PH-D (the penthouse at the Dream Downtown) around 10:30 p.m., the star and his pals (including Cosmopolis costars Stanley Tucci, Paul Giamatti, Kevin Durand and Sarah Gadon) parked themselves at a banquette near the DJ booth -- surrounded by six bodyguards.
Pattinson drank bottles of Budweiser as he chatted with other revelers -- and, with the doors opened to the outside terraces, he puffed on an electronic cigarette.
Leaving PH-D past midnight, the star and his group just moved the party downstairs -- to the Electric Room, a bar in Dream Downtown's basement -- for a few more drinks.
The fun, chill evening was about "celebrating with his friends and costars," a source explains to Us. Guests were treated to an open bar care of Ciroc vodka.
"It's really too bad that there was a cloud over his big night. He knows that everyone wanted to ask and bring it up," adds the source of Pattinson and Stewart's troubled romance. "He's ready for life after Twilight now -- now more than ever."