It's difficult to tell when filming ends and Robert Pattinson and Kristen Stewart's real-life romance begins in these pictures of the couple smooching on the Rio de Janeiro set of Breaking Dawn.

Robert/Edward and Kristen/Bella looked to be having a ball as they filmed scenes on the streets of the Lapa area of the city.

When they weren't grinning from ear-to-ear, they were enjoying their own private love carnival amongst the crowd of partying extras.

Production on the fourth film in the Twilight Saga has hit Brazil to film scenes for Edward and Bella's fateful honeymoon, where the still-mortal Bella falls pregnant with her vampire beau's baby.

Quite literally dozens of delicious pics below...