Robert Pattinson Reveals Breaking Dawn Sex Secret (video) 1“Twilight” star Robert Pattinson reveals that he was desperate to look good shirtless in “Breaking Dawn, Part 1,” especially for his love scenes with Kristen Stewart.

Rob would rather sit back, drink a beer and strum his guitar instead of working out. And he smokes cigarettes.

But he was motivated to get in better shape for the movie by co-star Taylor Lautner, who has a sleek muscled farm and rippling 8-pack abs.

“I had never been so worried about [how my body looked] before, but after seeing how much Taylor works out for the movies, I thought, ‘Well, everybody is really going to judge me now,’ ” Pattinson told Mexican magazine 15a20.

“I always tried to think about positions where I could tense the muscle, and suck in my belly.”

Lautner, 19, worked out obsessively and followed a high-protein diet to gain 30 pounds of muscle for “Twilight” sequels “New Moon,” “Eclipse” and “Breaking Dawn.”

Indeed, Taylor was in danger of being dropped after the first picture, because his character, Jacob Black, in the “Twilight” novels is 6’7″ tall and loaded with muscles.

But Taylor convinced movie producers he could muscle up. Jacob’s screen time has increased in subsequent films.

Taylor’s dramatic transformation motivated Rob, 25, to work out for six months prepping for Breaking Dawn’s honeymoon and love scenes, in which he appears shirtless.

“The body of the characters seem to be a big deal,” says the 6’1″ Rob, who plays the dashing vampire Edward Cullen.

“So in this movie, I thought, ‘Okay, it’s the last one, I’m getting a six pack,’ and I tried, but it’s very hard.

“I worked out so hard for six months, so after filming the sex scene, the first thing I thought was, ‘Time to eat!’ ”

Rob also had shirtless scenes in “New Moon,” and his six-pac abs were painted on by makeup artists.

Breaking Dawn, which co-stars Kellan Lutz and Ashley Greene, comes out Nov. 18, 2011.

Check out the video below.