"Well, that's 11.23 percent of the film finished," said Art Garfunkel after another day of hanging around spooky Viennese settings, standing in for Nicoles Roeg's obsessions.

Garfunkel, whose least well-known accomplishment is his master's in mathematics, is making his return to films in Roeg's "Illusions," a love story that director Roeg promises will be "high drama - no middle ground whatever."

Roeg and Garfunkel are both intense men who are unafraid to say how wrapped up they are in concern about love.

"In my personal life," Garfunkel says, "what I'm most involved wth is the mystery of how men and women go together. I deal with the question we all deal with: how to make love last."

"When you're in love," Roeg says, "you don't count the cost. When you tell her, 'we can't afford it, darling' - that's when she knows."

Roeg has located "Illusions" in Vienna because his protagonist is a psychoanalyst. One scene in the film will show Garfunkel and his costar, Theresa Russel, embracing on a couch in Sigmund Freud's office.

"Illusions" is a perfect title for a Roeg film. He's always made pictures that contain more than meets the eye. Gleefully, he points out the familiar trompe l'oeil poster on the wall of the Freud museum, the one that seems to show a profile of Freud, but on closer inspection actually shows Freud's forehead to be in the shape of a naked woman.

Roeg, 50, started making films late in life, and he's made very few. "Illusions" is his first outing since "The Man Who Fell to Earth" three years ago. His other films are "Performance" in 1968, "Walkabout" in 1970 and "Don't Look Now" in 1973.

As "Illusion" producer Jeremy Thomas says, "Roeg won't compromise, which is why he dosen't make a lot of pictures. The characters in this film aren't Americans just because that might make it play in Peoria. And it's Art Garfunkel, not a major box-office name like Richard Dreyfuss."

Harvey Keitel is the best-known name in the supporting cast. Theresa Russel was seen as Maureen Dean in CBS' eight-hour "Blind Ambition" in May.

Roeg does things his way or not at all. Last year he walked away from the biggest budget being offered any flimmaker at the time, Dino de Laurentiis' $25 million for a remake of "Flash Gordon."

"Dino and I had a trial run. I had a year to say what I wanted. At the end of it, he said that my plan wasn't the picture he wanted to make. It was the traditional artist-patron relationship. He was happy for me to stay, if I made his picture - but he'd have lost for me if I had." De Laurentiis hired Mike Hodges to direct, and the film is going ahead in London in May.

At first, it appeared as though "Illusions" would fall by the wayside too. Few directors film every project they'd like to, but for Roeg the disappointment is greater than usual because he generally spends a year or so collaborating with a writer on the script. His co-writer on "Illusions" is playwright Yale Udoff.

"Maybe it's a failing of mine," Roeg says, knowing it's not, "but I like to work on a script until it's close to the film I'm going to make, not just something to be read" and rewritten. Only Roeg rewrites Roeg.

The problem with "Illusions," from a financier's point of view, is that Roeg refuses to tell stories the way "Laverne and Shirley" does. Because there's more in his films than meets the eye, the brain has to be applied. As producer Thomas says, "All Roeg's films haven't been gigantically successful."

Roeg began "Illusion" as an artist in the employ of another Italian parton, Carlo Ponti. "Ponti gave me a story, and "Illusions' came out of that story, which was set in Italy. The story touched a major chord in my emotions and I took it to myself."

However, Ponti was unable to attract finance to the script. Even Roger Corman (for whose "The masque of the Red Death" Roeg had been cinematographer in 1963) was unable to find backers. By mid-1977 the project had "fallen into abeyance." The Roeg-Udoff script had become "just something to be read."

One of the readers was 28-years-old Jeremy Thomas, son of Ralph Thomas. The elder Thomas has directed dozens of films for the Rank Organization. The younger Thomas had produced "The South" for Rank, with Alan Bates, and it won the grand prize at Cannes last year.

Thomas, knowing that working with Roeg would be "another step up the ladder for me," asked Roeg if he would commit himself to make "Illusions" if Thomas could find a backer.

"I am committed," Roeg replied. "No one can make the picture without me".

Thomas bought out Ponti and convinced Rank to part with $4 million, in the hope that "Illusions" would "blow people's minds - Itmeans, blow a lot more people's minds than previous Roeg pictures."

Roeg is gleeful when he talks about Rank's gamble on him. After all, his previous film was the last made by British Lion before it went out of business.

Rank is well-cushioned, however. The studio can afford its recent aggressive more into financing films for international audiences, like "The Lady Vanishes," because it owns Britian's largest theater chain and holds the Xerox concession for Britian. It's the one major British studio that isn't headed by one of the Winodradsky brothers (Lord Grade at ATV and Lord Delfont at Emi). "I love Ed Chilton" (head of Rank's film division), Roeg says. "I've never met him, and I love him."

Garfunkel was cast for type, at least insofar as he says, "My character in 'Illusion' is a very careful man." He continues, "Some psychoanalyst treat the yesteryear of life as if it were nonexistent, believing everthing can be dealt with, contained. My character meets can experience - jealousy - which he cant't fit into the conventional explanations. He'd never come to grips personally with this problem. He'd never been put to the test".

Garfunkel is reluctant to talk further about "star-crossed lovers" that he and Thereas Russell play. "If I did, I'd turn the movie into just an exercise, a follow-through on what I had revealed to you."

Roeg feels that same way. If a certain line of dialogue from the scene in Freud's office were published here, he threatens, he'd cut the scene containing it from the film. In Roeg's mind, that would be like looking over a painter's shoulder, watching him do a few brush strokes, and then running out and telling the world all about it when there was nothing to tell.

Roeg maintains a very lighthearted set, like a painter whistling while he works. But he knows by now what can happen to his film if he dosen't watch out. The version of "The Man Who Fell to Earth" that was released in American had been cut by 23 minutes.

That pain has healed to the extent that Roeg can say now: "It's like a tailor-made coat. The customer takes it out of the shop and decides to rip one arm of the coat off.He walks around and no one says what an a - the tailor is." CAPTION: Picture, Nicoles Roeg and at right his star, Art Garfunkel: Intense men concerned about filming a love story.