Robert De Niro famously gained 27 kilos to play the boxer Jake LaMotta in "Raging Bull" while Leonardo DiCaprio slept in an animal carcass and ate raw bison liver in "The Revenant".
But few actors have gone as far as to live on the streets to research their role.
That is what Singaporean director K. Rajagopal asked of the star of "A Yellow Bird", his film which touches on some of the wealthy city-state's most sensitive issues of race, migration and sex.
Rising television star Sivakumar Palakrishnan spent his weekends living rough on the streets of Singapore's "Little India", exploring a rarely seen side of one of Asia's most ordered societies.
The delicately drawn arthouse movie, which premieres Wednesday at the Cannes film festival, follows an ethnic Indian man -- or a "black devil" as one of the film's Chinese characters calls him -- trying to rebuild his life and family after a spell in prison.
"I made him go out and live and sleep in the streets because he doesn't come from that side of the tracks," director Rajagopal said.
"It was quite tough for him but he did it. I wanted a fresh response, for him to feel what it was really like to be homeless. That is why I like him so much as an actor, he's very open and intense."
The film, which is showing in the Critics' Week section of the world's top film festival, also touches on the "simmering tensions beneath the skin" of Singapore's supposedly harmonious multiracial melting pot.
The struggling ex-con Siva has to sleep on the kitchen floor with his mother because she has rented out the bedroom of her tiny apartment to mainland Chinese migrants.
