Two films that for ages everyone was about to make but never did were Malcolm Lowry's "Under the Volcano" and the life of Nijinsky. While the volcano presumably still smolders, "Nijinsky" is at last under way at Pinewood Studios, with side trips planned to Sicily, Budapest and Monte Carlo. Herbert Ross is the director and his wife, American dancer Nora Kaye, is coproducer. The Rosses have been working on "Nijinsky" for 12 years.

During that time the reputation of Ross, a lanky ex-dancer and choreographer with a selflessly unobtrusive directing style has soared both among critics and at the box office. He may make the front office very happy these days but, he says, you can never make them happy enough to be indulgent. Even though Ross' "Turning Point" proved that ballet can have wide appeal, it was a task to get "Nijinsky" in the air.

Nijinsky's great period of international stardom lasted only five years; for more than 30 years, until his death in 1950, he was a madman attended by his wife, Romola. He was always a myth and an enigma, and people could not even agree on what he looked like: "Very quiet and rather ugly," said Lady Ottoline Morrell. "A serious man, beautiful looking," said Charlie Chaplin. He was the greatest male dancer the world has known.

To play Nijinsky, Ross cast an unknown American dancer of Russo-Argentine extraction, George de la Pena, who was Mikhall Baryshnikov's stand-in in "Turning Point." He is 22, Nijinsky's age at the time the film is set, and conveys on the screen a strong degree of lambent ambisexuality.

"George has really great artistry and is a remarkable actor," Nora Kaye says. "His dancing isn't as good as Baryshnikov's but he understands the character. Baryshnikov is older and too well known. If you are going to do a myth it's better not to have a preconceived idea of what it's like."

Italian ballerina Carla Fracci plays Karsavina. Leslie Browne, the ingenue dancer of "Turning Point," brings her stubborn-jawed innocence to the non-dancing role of Nijinsky's determined wife, Romola. Linking the other principals by his skill and commanding presence is Alan Bates as Diaghilev. Like Diaghilev, whose nickname was Chinchilla, Bates now has a white streak of hair and a thin mustache. "My God," said 74-year-old former Diaghilev protege Anton Dolin, when he saw Bates in costume. "I feel as if I'm 19 again."

Ross showed for the first time in "Turning Point" that ballet can work on film, but he modestly-limited himself to pas de deux and small groups. Now he is filming full ballets, with Bakst decors and costumes, a large corps from the London Festival Ballet and five cameras. The ballets chosen form a counterpoint to the script:

"Nijinsky never played a person who was in control of himself - 'Petrushka" was the most obvious example," Ross says. "He never played a human. He was a slave in 'Scheherazade,' an evocation in 'Spectre of the Rose,' half man and half beast in 'Faun.'"

The script, by Hugh Wheeler, is both cunning and humane. If the threads of the story never can be definitively unwound, he has made a convincing tapestry, limiting the action to just over a year beginning in 1912: the period of Nijinsky's greatest international triumphs and of his fateful marriage. Nijinsky's homosexuality is not glossed over: He was not an innocent seduced by Diaghilev but had been kept by a Russian prince and Polish count before he and Diaghilev fell in love. Their love is sincere but there is a suggestion that even without Romola's intervention it soon would have ended.

"I don't think Diaghilev wanted to get rid of Nijinsky, but he knew Nijinsky wasn't stable enough to lead the company." Herbert Ross says. Alan Bates agrees that Diaghilev's preoccupation was his ballet company.

The dances are not only essential to the plot: They are an act of piety on the part of Ross and Kaye, an attempt to preserve the choreography of Nijinsky's "l'Apres-midi d'un faune" ("It's brilliant and prophetic in its use of movement," says Ross) and the works and choreographic style of Michel Fokine, a style nearly forgotten since the Balanchine ascendancy.

The dancers have their shape; the lives in "Nijinsky," like most lives, seem to have none though Ross sees a theme. "I think it's about greed," he says. "Both Romola and Diaghilev loved Nijinsky but it was a worship of the object without realizing what the object was.

"Both of them confuse love with the pride of possession. Romola grew to love him. Diaghilev grew to the point where he didn't love him enough."