French Oscar winner Juliette Binoche stars as Auguste Rodin's ex-lover and muse who was confined to an asylum in the Berlinale contender "Camille Claudel 1915", a role she said attracted her for its extremes.
Binoche, 48, who picked up her Academy Award for her 1997 turn as a World War II nurse in "The English Patient", told AFP that she had exposed herself physically and mentally to play Claudel, who was a sculptor in her own right.
"The real challenge was to be completely bare in everything we showed -- the feelings, the landscapes, to be nothing, dumped alone in an asylum for 30 years," she said.
"At the same time this is a major artistic figure with an exceptional passion to create and it shows what life sometimes does to people who have the most to give."
Claudel, who left Rodin at the age of 30 when she realised he would never commit to her, spirals into a crisis after the relationship ends.
Her wealthy bourgeois family, unwilling to let her continue living and working in Paris on her own and repulsed by her eccentric behaviour and growing paranoia, have her locked up at an institution in Provence.
There she is surrounded by people with severe development disorders who moan and shout incessantly and need the most basic care. They were played in the film by actual patients.
Claudel stops sculpting, rarely speaks and begs the kindly director of the asylum to let her go.
But her younger brother, the writer Paul Claudel, who makes generous contributions to the institution, blocks her release.
Claudel would spend the rest of her life in the asylum, dying there in 1943 at the age of 79. She was buried in a mass grave.
Binoche spent three weeks with patients at the home to prepare. She said she struggled to find her place in the process, "to be close (to the patients) but not too close."
She said the mix of severe restraint in the character broken by fits of rage had been tough to modulate.
"You're completely silent and then there are two or three instances of shouting, as if all the words she had failed to say came out all at once," she said.
Director Bruno Dumont told AFP that he wanted to spotlight three days in Claudel's life, when she is still holding out hope that a visit from her brother could mean the end of her captivity.
"This is the darkest time of her life, when she is a recluse and all we know of her comes from medical records and correspondence" on which the film is based, Dumont said.
Binoche, herself the daughter of a sculptor, won the best actress award at Cannes in 2010 for her performance in "Certified Copy" by Iranian director Abbas Kiarostami.
She is up against two other grandes dames of French cinema at the 63rd Berlin film festival for prizes on Saturday.
Isabelle Huppert plays a 18th century mother superior who is sexually infatuated with a young novice in "The Nun".
And Catherine Deneuve will present on Friday "On My Way" about a woman her 60s who leaves her old life behind when she embarks on a spontaneous road trip.