The atmosphere of Francis Coppola's lamentable magnum opus, "Apocalypse Now," a ruinously pretentious and costly allegorical epic about war in Vietnam, recalls nothing so much as the notorious campfire scene in Mel Brooks' "Blazing Saddles." It's the cumulative effect generated by mixing richly portentous imagery with absurdly portentous prose, starkly portentous sound and flatulently portentous music.

The movie -- opening today in 70mm and supersonic Dolby at the Uptown -- commences straining for greatness and never lets up. It's still straining at the fadeout, which may not even be the definitive fadeout. The 35mm version of "Apocalypse," due next Wednesday at the Annandale and Beltway Plaza, supposedly ends with the display of fireworks Coppola preferred to omit from the 70mm version.

Coppola's woozy scenario leans desperately on a self-consciously "sardonic" voice-over narration, attribued to the author of "Dispatches," Michael Herr, whose vigorous literary style seems to turn bombastic when read aloud. The narration, full of premature commentary and character analysis, is underscored by risible orchestrations.

For example, the soundtrack reverberates with ominous buzzing as the woefully misconceived protagonist, a spook in Army uniform named Capt. Willard (Martin Sheen), consults the heavy dossier on a renegade Green Beret officer, Col. Kurtz (Marlon Brando), he has been instructed to locate and assassinate.

Once the pride of West Point, Kurtz has gone loco -- and native -- among the Montagnards somewhere up a river of no return in Cambodia. Willard's raspy voice quotes from a letter Kurtz sent to his son shortly after rebuffing the Army's attempts to recall and discipline him: "I am beyond their timid, lying morality, so I am beyond caring."

This lofty vanity inspires a flurry of buzzing from mysterioso organs and Moog synthesizers, exaggerating the ominous intimacy of Herr's text, which recalls the tone of old private-eye serials or the obligatory wake-up scenes in Raymond Chandler novels where Philip Marlowe returns to consciousness after taking another sap behind the ear.

"It was a real choice mission," Willard confides. "When it was over, I'd never want another." Whew! Later, in the course of a lengthy, inconclusive last-reel oration, Kurtz tells Willard, "It's judgment that defeats us." Like many remarks in the script, this one suggests that Coppola is muttering out loud, apologizing for his most conspicuous flaws.

Movies that remain in production and then in the editing room as long as "Apocalypse Now," growing so expensive and difficult to complete that there's little chance of recouping the investment in domestic theatrical release alone, almost invariably prove artistic fiascoes.

The extended Philippine location shooting on "Apocalypse Now" began Mar. 20, 1976. What with typhoons, illness, artistic disputes, Coppola's attempts to lick the potentially compelling but always boobytrapped original screenplay by John Milius and ordinary production problems associated with a big-budget adventure spectacle, the company lingered 15 months in the Philippines. The original $12- $14 million budget soared to an acknowledged production cost of $31 million, probably a cut-off figure chosen to stifle further press speculation.

Coppola, who supposedly mortgaged much of his property and future royalties from "The Godfather" to guarantee completion and retain control of the film, seems to have been painfully aware that his masterpiece-in-progress left something to be desired. "Notes," a remarkably revealing behind-the-scenes book drawn from a journal kept by Coppola's loyal, sorely tried wife Eleanor, quotes the filmmaker's memo to himself:

"My greatest fear -- I've had for months -- The movie is a mess -- A mess of continuity, of style -- and most important, the ending neither works on an audience or philosophical level. Brando is a disappointment to audiences -- the film reaches its highest level during the f-- -ing helicopter battle."

The finished film remains a mess of tangled, turgid continuity and florid, mock-operatic style -- at best a collection of production numbers and set pieces waiting in rain for a story capable of accumulating suspense and meaning.

The movie peaks early, both pictorially and metaphorically when Willard and the crew of a patrol boat assigned to ferry him up the river encounter Col. Kilgore, a cheerfully brutal, gung-ho air cavalry officer, played by Robert Duvall, who bombards a coastal village under VC control because he hears the surfing is great there. A conceptually preposterous episode, it nevertheless provides spectacular cinematic sport, with the helicopter gunships charging out of the clouds to "The Ride of the Valkyries," suggesting some neo-Wagnerian cross between the Dawn Patrol and John Ford's Horse Soldiers.

Idiotic as this airborne assault is (in real life it would surely earn the colonel a court-martial), it's a visual rouser and sums up whatever points the filmmaker has to make about wanton American violence in Vietnam. It's no accident that everyone ends up remembering Duvall's exultant "I love the smell of napalm in the morning . . . It smells like . . . victory." And no one can make heads or tails of the motives governing the major characters, Willard and Kurtz, one burnt-out case in pursuit of another; a self-defeating "contrast" if there ever was one.

Stripped to entertainment essentials, "Apocalypse Now" can boast a couple of thrilling action sequences and a trio of diverting supporting performances -- Duvall, the amazing Frederic Forrest as an agitated gunboat crewman called Chef and, in the unexpected comic highlight of the show, Dennis Hopper doing a hilarious turn as a zonked-out, sycophantic photo-journalist who has attached himself to the crazed Kurtz. Though he possesses greater inherent filmmaking ability, Coppola hasn't been nearly as astute as Ted Post and Karel Reisz, the directors of "Go Tell the Spartans" and "Who'll Stop the Rain," respectively. Their films were stripped for action, and as a result the implications had more impact and resonance.

Coppola's desire to say something significant -- even definitive -- about American military intervention in Vietnam is awkwardly apparent in his public statements about "Apocalypse Now" and in the platitudinous, navelgazing purple patches inflicted on the film itself. Instead of being embodied in the development and resolution of the story, what he thinks he wants to say is spoken in a husky, enigmatic stupor by Sheen and Brando.

Milius borrowed the plot outline for his screenplay from Joseph Conrad's "Heart of Darkness," then polished it off with a bloodbath cribbed from "The Wild Bunch." Incorrigibly indecisive, Coppola shot and discarded endings from both Milius and Conrad before settling on a vicious, meaningless denouement of his own invention. His apparent inspirations -- "Mondo Cane" and the more ritualistic samurai melodramas -- are on the debased side. Coppola even seems to transform himself into a morbidly pretentious Japanese director during the last hour or so of the film.

Conrad is the model Coppola should have trusted. The fatal dramatic mis-step in his scenario is the portrayal of Willard as a psychological wreck. Martin Sheen looks so over-the-hill-and-far-away from the outset that it plays havoc with the exposition when other characters -- notably the officers who send Willard after Kurtz -- don't seem to notice, or when we're supposed to accept Willard's narration as world-weary, tough-guy wisdom.

Since Willard is depicted as merely a younger example of the corrupted Kurtz, the movie quest is immediately robbed of a humane perspective, a sense of mystery and a revealing climactic confrontation.

Aided by Vittorio Storaro's sinister chiaroscuro lighting and Dean Tavoularis' elaborate and increasingly farfetched sets, culminating in a replica of Angkor Wat, Coppola labors to sustain a surreal, nightmarish illusion of war-torn landscapes and moral rot. However, the sets tend to upstage and contradict the motley, schematic dramatic episodes they play host to.

This incongruity is especially noticeable in a tawdry episode about a U.S.O. troupe of dirty-dancing Playboy bunnies, and in a later encounter with supposedly grim, isolated G.I.s at a contested bridge that Storaro has inexplicably lit to suggest Christmas in Rockefeller Center.

The theoretical scheme of a descent that reveals more vile forms of corruption and madness the farther upstream we navigate is never realized. And when Brando, bald and obese, is finally sighted -- like Moby Dick -- among Storaro's exquisitely obscuring shadows at the Kurtz encampment, there's nothing left but the camp diversion of listening to him recite from T. S. Eliot and speculating about the sacrificial finale. He doesn't get as far as "Mistah Kurtz, he dead," unfortunately.

Coppola, a typically feckless Hollywood liberal, probably took on the project thinking of himself as an anti-war moralist and a stern foe of American imperialism. But the film owes most of its vitality to the fundamental pictorial excitement of combat scenes and reflects Milius' reactionary ideology with peculiar clarity. Taken at face value, the script seems to imply that Kurtz could have been the Patton of Vietnam if only small-minded superiors hadn't interfered. Coppola helped write "Patton" several years ago. On "Apocalypse Now," he got to command a make-believe army.

If Coppola intended to contradict the Milius view of Kurtz, his interpretation got mislaid -- probably because he started perceiving the movie as his own psychodrama. Eleanor Coppola testifies that "We had long conversations about the themes of the film. We talked about opposites, about power and limits, good and evil, peace and violence . . .

"We talked about how the film was a parallel for the very things that Francis was living out this year. How he had been Willard setting off on his mission to make a film and how he had turned into Kurtz for a while. I thought when he resolved the conflicts within himself, he would see the end of the film clearly."

Evidently, he never did; and "Apocalypse Now," despite flashes of excitement, remains a colossal egocentric blur.