Some critics are calling “Mojave’’ an example of good old-fashioned noir. But not the movie’s writer and director, Bill Monahan, who bristles at the description. “I don’t like genre work,’’ he says, “I figure it’s my special job to smash it up whenever I get near it.’’ In truth, “Mojave,’’ which opens at the Brattle Theatre Friday, is a little bit of everything: noir, thriller, drama, and comedy. (The funniest moments belong to Mark Wahlberg, a buddy of Monahan’s who plays a petulant Hollywood producer.) Monahan, who resides these days on the North Shore, is best known as the Oscar-winning screenwriter of “The Departed,’’ but he had an established career in Hollywood by then, having written the script for Ridley Scott’s 2005 epic “Kingdom of Heaven.’’ “Mojave’’ stars Garrett Hedlund as a brooding director who takes a trip to the desert and finds trouble in the form of a sinister drifter played by Oscar Isaac. Monahan said it was a treat to direct his own script. “The job of the writer is to do something on paper that would be credible as a motion picture,’’ he says. “I’m where I am as a screenwriter because I write in a highly visual way. You can usually see a movie in my scripts and that tends to get things made.’’ Asked how he would characterize “Mojave,’’ Monahan took a drag on his cigarette. “I think my model is always ‘Hamlet.’ As a genre, it’s superficially a revenge-tragedy. But there are more jokes in ‘Hamlet’ than in almost any other thing. There must be something to it because it’s been putting asses in the seats since 1599.’’