FROM IDOL TO ACTOR : O'DONNELL REACHES NEXT LEVEL WITH THE HELP OF HEMINGWAY.

Byline: Bob Strauss Daily News Film Writer

The physical resemblance between Chris O'Donnell and Ernest Hemingway is astonishing.

The temperamental resemblance between the hot young actor and the legendary author is, well, just about nonexistent.

``Chris O'Donnell was it. He was always the only one because he looks so much like Ernest Hemingway,'' says Dimitri Villard, the producer of the new movie, ``In Love and War,'' which is based on his late father Henry Villard's memoir, ``Hemingway in Love and War.'' ``If you see photos of Chris O'Donnell and Hemingway at that age, they could be twin brothers. It's absolutely eerie.''

While O'Donnell shrugs off the superficial similarities (besides looking alike, both men hailed from suburban Chicago), the actor so well-known for his sensible lifestyle and nice-guy demeanor would be far more alarmed if he shared personality traits with the volatile Hemingway.

``I think I would be more similar to Hemingway at this stage in his life, as opposed to when he's older and is a more self-destructive, bitter guy,'' O'Donnell, 26, admits. ``But I had to show the seeds of that bitterness. At the end of this movie, he's been changed by this experience. Something in him just kind of snapped. He got his heart broken and never really recovered.''

The film recounts events in the closing months of World War I, when a teen-age Hemingway, Henry Villard (played in the film by Mackenzie Astin) and nurse Agnes von Kurowsky (Sandra Bullock) were all American Red Cross volunteers on the Italian front.

Ambulance-driver Hemingway, the first American wounded in that theater of operations, almost lost a leg to Austrian shrapnel. Von Kurowsky was instrumental in saving the future adventurer's limb; when a case of jaundice landed Villard in the hospital bed next to Hemingway's, the future diplomat was able to observe the blossoming romance between the brash young writer and the beautiful older nurse.

But the wounded Hemingway was shipped back to Illinois and, after the war, von Kurowsky stayed on in Italy for a time, rejecting her young suitor for an aristocratic Venetian doctor.

A decade later, Hemingway romanticized these wartime events in his classic novel, ``A Farewell to Arms.'' For her part, von Kurowsky went to her grave claiming that her relationship with the kid, as she called Hemingway, was never more than platonic. But after her death, von Kurowsky's widower gave her longtime friend Villard letters and a secret diary that painted a much more passionate picture.

Which, after being turned into a book and screenplay, fired a passion in the usually reserved O'Donnell. And his agents.

``My manager had read the script and thought it would be a great part for me, which I agreed with,'' says O'Donnell, who has spent much of his movie career playing juvenile foils to the acting pyrotechnics of Jessica Lange (``Men Don't Leave,'' his 1990 film debut), Al Pacino (``Scent of a Woman''), Gene Hackman (last year's John Grisham misfire, ``The Chamber'') and, as Robin the Boy Wonder, to two different Batmans: Val Kilmer two years ago and George Clooney in this summer's ``Batman and Robin.'' ``As soon as we heard that Richard Attenborough was interested in directing it, though, we really went after it and tried to make it real.''

An actor himself, ``Gandhi'' Oscar winner and ``Jurassic Park'' star Attenborough has directed many an acclaimed performances, including career-makers for young stars such as Denzel Washington (``Cry Freedom'') and Robert Downey Jr. (``Chaplin''). After getting lukewarm critical response to his first serious adult role in ``The Chamber,'' O'Donnell could hardly have been in better hands.

A seasoned judge of both talent and career strategies, the 73-year-old filmmaker had some pretty good notions of what O'Donnell needed and was capable of.

``Chris's nice, well-adjusted kid label is accurate, but it shouldn't disguise a very major strength and determination to do what he wants to do in the way that he wants to do it,'' Attenborough says. ``In playing Hemingway, who's very full of his own importance and ego and pride and stubbornness and ruthlessness, Chris comes through with all of that in the movie. You really see, in embryo, this very bile-dominated character.''

That's called acting. By all accounts, O'Donnell is such a good-natured straight arrow that he makes most Hollywood actors twice his age look like brats.

The youngest of seven children, O'Donnell was educated in Catholic schools, worked to complete his marketing degree at Boston College even as his acting career took off and still lives in Chicago, close to his childhood buddies and away from the Hollywood spotlight.

About the biggest trauma so far has been his relatives' inability to understand Chris' disdain for celebrity. But they all get it now.

``At first, they were real proud of me, but then they would give me a hard time for not wanting to talk to people about it, because I'd just get bombarded wherever I went,'' O'Donnell recalls. ``But now it's gotten to the point where they're getting tired of being bombarded - `That's Chris O'Donnell's brother!' `That's Chris O'Donnell's sister!' - and they're getting tired of that being all anybody wants to talk to them about! Now they appreciate what I go through.''

Still, they all love coming together for the kid brother's movie premieres - which, O'Donnell points out proudly, are among the few events that can still draw everybody in the large clan to the same place at once.

``I don't know if it always goes hand in hand, but it appears to me that Chris is some kind of advertisement for having a great family,'' says Joel Schumacher, director of O'Donnell's two ``Batman'' movies. ``He's one of the healthiest young people I've ever worked with in this business. He wasn't attracted to this industry for the damaged, dysfunctional reasons so many are. He's ambitious in the right way: ambitious for what he's doing, not for fame and fortune.''

Nor, evidently, to meet girls. While leading ladies ranging from Drew Barrymore (``Mad Love'') to ``Love and War's'' Bullock express unbridled affection for O'Donnell, it's purely of a ``he's a great pal'' nature. He attributes his companionability to the influence of four sisters and has exclusively dated schoolteacher Caroline Fentress through most of his teen idol years - and proposed to her last fall. Again, unlike the oft-married Hemingway, he plans to only do this once.

And hopefully this year, soon after the seemingly endless ``Batman and Robin'' shoot is over - a process that has been delayed by O'Donnell's co-star and basketball partner Clooney's recent, hoops-related sprained ankle.

Not that he's in a super hurry for the superhero gig to end.

``I like playing Robin and hope I get a chance to do another one of these movies,'' the aging Boy Wonder says. ``I could never imagine, as a kid, that I'd get to play a superhero in a movie. I look at my nephews when they watch them, see how their eyes light up, and it reminds me of how I reacted to movies when I was that age.''

Still, there comes a time to put away childish things. And even though ``In Love and War'' catches the melancholy, misogynistic and ultimately suicidal Hemingway at a decidedly immature point, O'Donnell sees the role as a kind of actor's graduation rite.

``Ernest is the most complicated character I've ever played,'' he says. ``You really see him going from a young, cocky, naive kid into this other kind of person. That's what makes it interesting.

``A film like `Batman,' which is more action-driven, is a different experience,'' O'Donnell notes. ``Not to take anything away from `Batman,' but this is more satisfying. I'm just trying to continue to grow and challenge myself. I don't know in what particular direction it'll pull me, but whatever it is, I hope I'll continue to do stuff that challenges me and not just go through the motions.

``Otherwise, what's the point?''

CAPTION(S):

3 Photos

Photo: (1--Cover--Color) THE importance of being Ernest

Chris O'Donnell's portrayal of the young Hemingway is his graduation to complicated roles

(2) Chris O'Donnell already knew he wanted to play a teen-age Ernest Hemingway in ``In Love and War,'' but Richard Attenborough's interest in the project really piqued the 26-year-old actor's interest.

(3) ``In Love and War'' features O'Donnell as then-ambulance driver Ernest Hemingway and Sandra Bullock as the nurse who helped him recover from battlefield wounds suffered on the Italian front.