`Rain Man': Hoffman in monochrome role. Tom Cruise co-stars in comedy-drama hopefully started by five directors

``Rain Man,'' the new comedy-drama with Dustin Hoffman and Tom Cruise, had a bumpy history before finally getting to the big screen. No fewer than four major directors, including Steven Spielberg and Martin Brest, dropped the project before Barry Levinson took it on as his first project after ``Good Morning, Vietnam.'' It's not hard to guess why the undertaking turned out to be so tricky. The main characters are anything but conventional heroes: One is a mentally handicapped man who's spent his life in institutions, while the other is a hustler with a loud mouth and a volatile temper. The story isn't conventional ``buddy movie'' material, either. It focuses mainly on a long, slow journey from Ohio to California, spent largely in motels and other nondescript places.

What makes the film newsworthy is its offbeat performance by Mr. Hoffman, who's a brave actor as well as a good one. His career has included some roles that seemed automatically suited to him - his first big success as Benjamin in ``The Graduate'' is a prime example. But he's also taken parts that required gigantic stretches, from Ratso Rizzo in ``Midnight Cowboy'' to his last major enterprise, ``Death of a Salesman,'' where this fairly young and very sturdy man played the old and broken-down Willy Loman - and played him brilliantly, on the Broadway stage and in a video version of the same production.

But nothing quite prepared me for Hoffman's work in his new picture. I knew in advance that his character here, named Raymond, would be a man with abnormal ways of thinking and behaving. I didn't guess that Hoffman would play this unusual character in a completely uncompromising way, however, making no attempt to give him the slightest hint of sophistication or movie-style appeal.

Raymond has talents, to be sure. He is handicapped in many ways - he's called an ``autistic savant'' by a psychiatrist character - but he's light years ahead of so-called ``normal people'' in some areas, particularly in matters related to arithmetic and feats of memory. What's fascinating is that Hoffman never strains to make Raymond cute or amusing or ``delightfully different.'' Instead he plays Raymond almost painfully straight, so that when the character does charm us, the effect is all the more striking for being so unexpected.

The story of ``Rain Man'' takes place largely on the road, as Charlie escorts Raymond to California in hopes of cashing in on Raymond's inheritance from their father. This plot isn't very interesting in itself; it's mostly an excuse for the brothers to interact for a couple of hours, revealing their personalities to us and getting to know each other better than anyone could have expected.

They have a number of small adventures in cars, motels, and a gambling casino. Along the way, Charlie slowly learns to cope with his brother's eccentricities: Raymond won't fly in airplanes or go out in the rain, for instance, and when he feels nervous he rattles off Abbott and Costello's old ``Who's On First'' routine, a habit that might drive any companion up the wall. Even more gradually, Charlie learns to love his impossible but truly lovable big brother, until the rough edges of his own abrasive personality start to smooth out, as well.

``Rain Man'' is not a major film. The story wanders, the plot twists seem contrived at times, and the emotions are never as intense as they might be. But it highlights yet another facet of Hoffman's talent: a gift for monochrome, of all things! And it has a heart as good as Raymond's own, which is more than a lot of Hollywood movies can say for themselves at the moment.