American actress Sandra Bullock and Mexican film director Alfonso Cuarón have presented their upcoming thriller film ‘Gravity’ at Comic-Con in San Diego. Bullock spent more than six months preparing physically for the role as an astronaut, which required her to spend hours in a small cube that simulated zero gravity. She said she had to be really creative: “You learn that the imagination is a very important tool. We had sound. It was all done in pieces, out of sequence. So they’d be like, ‘OK, this is when the debris almost ripped through your chest, and this is where this happened and now get to that point, but keeping your body in this exact position starting and in five seconds ending in this position here’. And you have to match it otherwise it can’t seamlessly be sown into the film.” Director Alfonso Cuaron praised her athleticism in the role: “I think that’s when Sandra brought all her dancing background. Everything had to be so precise, you know like a ballerina.” The film, which also stars George Clooney, is about two astronauts who attempt to return to Earth after debris hits their space shuttle, leaving them drifting alone in orbit – with no communication from Earth. Although the trailer has audible explosions in it, the director has confirmed that scenes in space will be silent as there is no sound in space. Gravity is set to open the 70th Venice International Film Festival in August before being released in October.