As if the god of TV movies had smiled upon the city, a steady snow fell yesterday as a blanket-shrouded Martin Sheen crouched over a heat vent on the Ellipse.

"The main thing from the director's point of view is the breath," said a shivering Deborah Levine, coproducer of the docudrama based on the work of activist Mitch Snyder and starring Sheen. Levine puffed out a little white cloud into the frigid air to illustrate why the director had nothing to worry about on the second day of filming.

"That was our main concern -- would we have breath?"

They had breath. They also had what one company member called "real homeless" as paid extras, and shopping carts filled with old brooms and newly purchased umbrellas as props for Sheen's costar Cicely Tyson, who plays a homeless woman. They had gloves and parkas and hats and ski masks and three layers of long underwear and Winnebagos to huddle in between takes and hot soup and hot chocolate and hot tea (Tyson insisted on tea, not coffee, in her grate scene, a request that sent a tiny horde of functionaries racing).

A clapperboard with the title "Samaritan" slapped shut. "Action!" Silent extras playing everyone's idea of Washingtonians jumped up and down in their camel-hair coats and business suits to keep the circulation going. Several other professional actors, a bit too healthy beneath their dirty afghans and crumpled hats, served as an observing chorus of homeless for the scene.

"Looks like poor old Esther Gore finally cashed it in," an actor in a police uniform said into a walkie-talkie as the tan Sheen, wearing an army jacket and jeans, looked down on the body of an actress playing a dead homeless woman.

"Esther Gore's my stepmother's name," whispered scriptwriter and producer Clifford Campion with the smile of a small boy who has pulled off a good one.

Snyder stood nearby in the original army jacket and jeans Sheen had copied, but without the tan. A green, dirt-freckled blanket protected his shoulders. "I found whenever I wore a winter coat, it would only last 10 minutes," he said. "Someone else would be cold and I'd give it to them. I haven't worn a coat in four or five years."

Sheen was draping a blanket across the prone body again and again as the scene was reshot and reshot. Several feet off, a man communing with some tiny knobs on black boxes sat below a green-and-yellow cafe umbrella advertising "Bell' Agio, the soft, easygoing white wine."

"I can see Mitch getting upset about some things," said Paul Fine, who coproduced with his wife Holly the 1984 "60 Minutes" piece on Snyder that prompted Hollywood's interest in Snyder. Fine was a paid consultant for the movie. "It's always strange to see someone playing you. And actors -- they can't know about all this. I can see him look tense at times, but he's staying out of this now like I am."

Staying out of it, however, doesn't preclude talking with Sheen, whom Snyder and mutual friend Daniel Berrigan convinced to do the movie despite the actor's hesitations about the script, which he considered too mild.

"Martin is the person we share the most with politically," said Snyder. "Martin is working very, very hard. We understand we're working under severe limitations. You talk about commercial television and everyone understands. But the movie adds a bit of substance to human beings who have become very, very soft and invisible. Like that steam, they just sort of drift away.

"It's essential we get in the movies, on 'Entertainment Tonight,' anywhere. Then people hear about the homeless where they don't expect it. Their defenses are down a little bit."

"Dick, I'm not sure I'm going to need your smoke!" director Richard Heffron shouted to a crew member. Tyson and Sheen were scheduled to sit on a grate rigged with artificial smoke, but apparently it was sufficiently steamy au naturel.

Unrecognizable within layers upon layers of rags, her mouth sunken as if all her teeth were gone, her eyes framed by strands of dirty gray hair, Tyson limped down the block toward Sheen, who lay on the steaming grate, a volume of Thomas Merton in his hand.

Tyson joined the picture just a few weeks ago, after CBS intimated that only another big star could make such an uncommercial movie financially palatable.

"A blanket for this gentleman!" yelled the assistant director when someone realized Sheen was without the required outerwear. Another functionary was bustling -- Tyson needed sparkling water in her Winnebago.

As the afternoon passed, the snow thinned and finally ceased to fall, but the plumes of frozen breath remained.

A block away, a woman about Tyson's age walked. Two bedraggled skirts, layered one upon the other, flapped about her legs. Her hands clutched a plastic bag and a dirty canvas satchel. She stopped and looked around as if confused, talking to herself or perhaps to an invisible companion. Then, slowly, she took another step, resuming her passage along the slick sidewalk.

Back on the set, it was almost time for lunch break.