Michael Bay, director of the blockbuster Transformers trilogy and other huge hits ( Bad Boys 1 and 2, Armageddon) smiles when you tell him Pain & Gain — his self-described “small movie” shot entirely in South Florida on a budget of $26 million (buoyed by a $4.2 million tax break by the state) — is one of the oddest films to come out of Hollywood in years.

“This is a weird movie,” the director said during a recent stop at the Mandarin Oriental to promote the film in Miami. “This is not the kind of movie the studios greenlight much anymore. I wanted to do something small and quirky. But because I’ve made Paramount [Pictures] billions of dollars with the Transformers movies, I told them, ‘I’m going to make this movie.’ They said ‘Why do you want to make it?’ They were scared of it. But I saw something unique in this material. The best compliment I’ve heard from audiences who have seen it is ‘Wow, that was really different.’ Which is cool, because it was intended to be a bizarre movie.”

Pain & Gain, which opens Friday, is certainly different from anything Bay had directed before: It is character-based and performance-driven, with only one brief action sequence and, most shocking of all, just a single, rather puny explosion. In Pain & Gain, the story is wild enough to eliminate the need for pyrotechnics.

Based on an epic three-part story by Pete Collins published in the Miami New Times in 1999 and 2000, Pain & Gain centers on three bodybuilders — Daniel Lugo, Paul Doyle and Adrian Doorbal — who embarked on a crime wave in 1994 involving fraud, theft, kidnapping, torture and murder. The sprawling case got weirder and stranger as it unfolded, culminating in a grisly act of dismemberment by chainsaw and hand axe.

There were too many people involved in the case to squeeze into a single movie, so screenwriters Christopher Markus and Stephen McFeely, who previously collaborated on Captain America: The First Avenger, had to condense and simplify the story, eliminate some characters (Lugo had a wife and an ex-wife with four adopted children) and turn others into composites.

In the hands of Martin Scorsese or Michael Mann, the script for Pain & Gain might have resulted in a bloody crime saga, a la Goodfellas or Heat. But Bay read the screenplay and saw something different: A pitch-black comedy about the American Dream, with a body count.

“When I read the article, the story was so absurd that it laid out comical,” he says. “When you try to use a chainsaw on someone’s head to dispose of a body, and it doesn’t work so you take it back to Home Depot with human hair on it — it’s so bizarre that it’s funny. It’s like those videos of dumb criminals doing really stupid things that get millions of hits on YouTube. I think people like to watch train wrecks.”

Some of the survivors of the murder victims and law-enforcement officials have been dismayed by the trailers and TV spots for Pain & Gain, which are overtly comical and don’t really hint at the darkness of the story.

“What Hollywood is going to do Hollywood is going to do,” Miami-Dade State Attorney Katherine Fernandez Rundle told The Miami Herald in an interview earlier this year. “My thoughts are with the victims. To trivialize this horrible tale of torture and death makes a mockery out of their lives and the justice system.”