Patrick Dempsey boards ‘Transformers 3’

Director Michael Bay will begin lensing this month

Patrick Dempsey has revealed he’s joining the cast of Paramount’s “Transformers 3.”

In confirming the casting news, Par said director Michael Bay will begin lensing the third pic this month.

Three-quel reteams Bay with franchise stars Shia LaBeouf and Megan Fox. “Transfomers 3” is set to unspool in theaters July 1, 2011.

Dempsey will play the boss of Fox’s character. Dempsey told reporters in Brazil this week that it’s a “dark character.”

Dempsey won’t be arriving on the “Transformers 3” set right away. First, he’ll shoot indie pic “Flypaper,” a crime-comedy about a man caught between two holdups at the same bank who is in love with one of the bank tellers. “Hangover” scribes Jon Lucas and Scott Moore penned the script.

Dempsey, star of ABC’s “Grey’s Anatomy,” was last in theaters with romantic comedy “Made of Honor.”

He’s repped by UTA.