WALT DISNEY'S "Snow White and the Seven Dwarfs" has returned for its seventh revival at a time when the enchanting cinematic form it pioneered--feature-length fantasy animation--is in jeopardy.

Last summer, two new films, Don Bluth's "The Secret of NIMH" and Steven Lisberger's "TRON," attempted to revitalize the Disney traditions, but neither was a commercial success. That makes it even more unlikely that any organization, no matter how dedicated, will commit itself again soon to such a costly gamble on the outside chance of creating a classic movie fantasy.

"Snow White" was a triumphant breakthrough when Disney completed it in 1937. But if he had realized the cost of producing a full-length feature in animation, this particular dream might not have become reality. "Snow White" threatened to bankrupt Disney when the costs escalated from an estimated $500,000 in 1934, when the project was launched, to $1.5 million upon its completion shortly before Christmas of 1937. The project was nicknamed "Disney's Folly" by some unknown wag and evolved into a heroic, communal gamble during its four-year gestation period at the studio, whose survival depended on its success.

Modern audiences scarcely can avoid approaching "Snow White" as something that belongs to the past. Even if they like the picture, it probably gives off a faintly quaint, old-fashioned aroma. Yet animated films of the present look chintzy and unimaginative compared with the standards Disney set in the past.

Perhaps half of the brisk, 83-minute running time consists of episodes that can be savored as cartoon set pieces: Snow White's nightmarish flight into the forest after being warned of her stepmother's hatred, for instance, or the "Whistle While You Work" number, in which Snow White and the woodland animals clean the dwarfs' cottage.

Atmosphere, character and comedy predominate in these episodes. The Disney animators were exceptionally skillful at phantasmagoric and comic sequences. They were also rather audacious about juxtaposing scary and funny bits. For example, the transformation of the queen into the crone who will offer the poisoned apple to the unsuspecting princess conveys a delirious sense of diabolism at work. Simultaneously, the animators dare to kid their own effects by showing us a raven so terrified by the queen's metamorphosis that he hides out in a skull, his own eyes staring brightly out of the empty sockets.

Even at a high point of suspense, with the dwarfs and the animals racing through the forest in an attempt to reach Snow White before she bites into the apple, the filmmakers find time for comic bits that increase the suspense by virtue of their incongruity. It's this comic technique that contemporary directors like Steven Spielberg and George Miller have also mastered while scaring the daylights out of you.

DISNEY HAD both esthetic and economic reasons for launching the project at the time he did. His animators, chained to the eight-minute format, could not be expected to keep up their enthusiasm indefinitely if they were obliged to keep a stock company of even beloved cartoon characters in hilarious situations 12 to 18 times a year. In addition, these shorts were booked at flat rental rates; if Disney produced a feature, he could get a percentage of the box-office receipts.

Disney received crucial moral and financial support from two sources: On the basis of early rushes, W.G. Van Schmus, general manager of Radio City Music Hall, guaranteed a booking at the plush theater. And Joe Rosenberg of the Bank of America, after sitting noncommittally through an incomplete rough cut, nervously narrated by Disney himself, calmly remarked, "That thing's going to make a hatful of money," and approved the $250,000 loan needed to complete the picture. Premiered at the Cathay Circle Theater in Los Angeles on Dec. 21, 1937, "Snow White" created a legendary sensation before a gala audience that included spectators like Chaplin, Gable, Dietrich and Garland.

First released nationally a month later, the film went on to record a domestic gross of $8.5 million. At that time the average admission price was about 25 cents (10 cents for children). The popularity of "Snow White" allowed Disney to pay off the company's debts, purchase the current studio site (a 50-acre property in Burbank priced at $100,000) and lavish $2.5 million on the production of "Pinocchio."

The gambling aspects of this type of film haven't changed today. A fully animated feature still requires hundreds of thousands of illustrations consisting of a photographed color illustration for every frame of film. The next Disney animated feature, "The Black Cauldron," has been in development since the mid-'70s and production, now about a third completed, will continue into early 1985. A second project, "Basil of Baker Street," now is in the screenwriting stage and won't appear before 1987 at the earliest. Animated features will be a rarity even from the one production source that appears capable of sustaining the form.

Don Bluth consciously attempted to reawaken the communal spirit of the early Disney studio while "The Secret of NIMH" was in production at his own compact little plant in Studio City, Calif. But by the end of 1982, "NIMH" had returned only about $5 million in domestic rentals against its cost of about $7.5 million. Ever resourceful, Bluth is now attempting to recoup by using full cartoon animation in a new video arcade game called "Dragon's Lair," scheduled to be introduced this month. If it's successful, Bluth plans to devise others and use some of the profits to help finance his animated features. At the same time, the games would serve as a training ground for animators, roughly comparable to the situation that existed at the Disney studio 50 years ago, when "Snow White" was enriched by the talents of animators contributing regularly, and often brilliantly, to the "Mickey Mouse" and "Silly Symphony" cartoons.

There doesn't seem to be much point in looking for inspiration from other sources. The dreary "Heidi's Song" put feature animation plans at Hanna-Barbera under an instant pall. Martin Rosen, the producer of "Watership Down," recently abandoned plans to film another Richard Adams novel, "Plague Dogs." John Korty's "Twice Upon a Time," a fantasy in some kind of cutout animation technique, evidently is considered unreleasable by its patron, the Ladd Company. As far as one can see, animated features are a high-risk form that only the Disney organization can afford failing at. And what makes this exclusive luxury possible is the existence of the illustrious backlog that begins with "Snow White and the Seven Dwarfs."

THE FILM evolved during a period of prodigious comic invention and stylistic refinement in the Disney studio's cartoon shorts. Not a year passed in the 1930s when Disney failed to win the Academy Award for best cartoon. The studio was undoubtedly ready for the challenge.

Disney, while expanding to feature length, was careful not to let the exposition interfere with the exuberance of the cartoon format. In fact, he succeeded in merging the old format into an incisive, sustained fairy tale plot. "The original Grimm Brothers' version had to be considerably cut," he recalled. "Without cutting, there would not have been room for our sort of fantasy, our sense of humor, and the creation of our personages."

The finished product shows very little slack and an abundance of diverting incidents. The attributes of the animals and dwarfs are worked out with extraordinary charm and detail. For example, elaborate slapstick routines are devised around the way Snow White's friendly critters use their tails and their wits to help clean the cottage. A ponderous turtle provides a delightful crawling gag by always arriving too late for whatever assembly the other animals have concluded. And, invariably, there are those uncanny touches of child psychology, deftly calculated to get little ones where they live, like the moment when Snow White wonders if the dwarfs might be orphans and a baby deer nuzzles its mother.

Perhaps the loveliest single poetic touch comes in the scene where the dwarfs and animals are mourning Snow White. The tears running down the cheeks of the dwarfs are linked with the candle wax running down the tapers and raindrops running off the hides of the animals, who keep a vigil outside the cottage. Indeed, this is a kind of visual poetry that may only work in animation; live-action might reduce the same conceit to soggy banality.

Music was an integral part of the Disney style from the outset. The "Snow White" score, composed by Frank Churchill and Larry Morey, includes at least three songs that became a part of everyone's pop culture heritage: "Whistle While You Work," "Heigh-Ho" and "Someday My Prince Will Come." Snow White and Prince Charming have their outmoded and sometimes trying juvenile operetta tendencies, but of course this was a period in which Jeanette MacDonald and Nelson Eddy were still going strong, and the gush quotient is pretty mild.

Modern screening techniques have made the movie look a trifle funny at the top and bottom of the frame, where bits of the original compositions are cut off for wide-screen projection. Shot in the old ratio of 1:33 to 1, "Snow White" is now printed as well as projected at a ratio of 1:75 to 1. The defacement is relatively slight as these outrages tend to go, but it's also immediately apparent: The camera must move up and down to catch every word of a prologue printed on the pages of a storybook.

Once again, I'm compelled to ask: Is this defacement really necessary? Aren't there exhibitors somewhere proud enough to insist on showing a treasure like "Snow White" the way it was meant to be shown?