Sandra Bullock's 'Gravity' Director: Filming Was Very Intense

Sandra Bullock carries a big present while escorting her son Louis to a birthday party at Fun & Fit Gymnastics on Sunday (July 28) in Burbank, Calif.

The 49-year-old actress emerged later, holding hands with her little guy, who scored a yellow balloon as a goody from the party!

“It was a very intense experience for Sandra, I must admit,” director Alfonso Cuaron said (via EW) at the 2013 Comic-Con panel for their film Gravity. “It required for her to be isolated..Outside there were robots holding the camera, in some instances the robot would be holding the lights.”

“Sandra was completely insulated in that cube,” he added about her filming in this cube device to mimic a space ship. “Sandra chose to just stay in there between takes … as Sandra said, it was very mathematical.”

25+ pictures inside of Sandra Bullock and Louis going to a party…