PETER WEIR is the first potentially important director to emerge from a phenomenon called The New Australian Cinema.Though still tentative and modest, this renewal of indigenous, serious dramatic film making among a group of young Australians has created enough of a stir, particularly at the Cannes Film Festival for the past few years, to deserve a name and excie curiosity.

Now that Weir's second and third full-length features, "Picnic at Hanging Rock" and "The Last Wave" respectively, have been acuqired for American theatrical release, audiences here will finally have the opportunity to begin familiarizing themselves with the Australians. Weir's pictures leave an exceptionally promising impression. They don't bowl you over, but they demonstrate an attractive and imaginative flair for the medium, suggesting that something is going on Down There, perhaps something that will produce a distinctive, impressive body of work by allowing native talent to mature on native soil.

"The Last Wave," a fascinating psychological thriller weakened in the last analysis by rampaging apocalyptic undercurrents, opens this Wednesday at the Dupont Circle. The earlier "Picnic at Hanging Rock," at once a more haunting and satisfying exercise in ominous mystification, dealing with the unsolved disappearance of schoolgirls enrolled at a turn-of-the-century finisning school in the Victoria countryside, is scheduled to arrive March 7 at the Avalon.

Weir seems to be drawn to macabre, weirdly unsettling material. His first full-length feature, "The Cars That Ate Paris," was a horror comedy about a degenerate community in the outback whose economy depended on creating and exploiting auto accidents. A critical favorite and popular flop at home, it proved instrumental in attracting international attention to the Australians, in part because Weir and his producers, Hal and James McElroy, took it upon themselves to advertise the film's presence at Cannes in 1974 by driving around in a Volkwagen covered with spikes. Having helped engineer the breakthrough at Cannes, Weir recently came to the United States to help advance the American openings of "Wave" and "Picnic," whose reception may determine how many other interesting Australian how tures get here in the immediate future.

Slim, fair-haired, hawk-nosed and soft-spoken, Weir suggests an earnest collegian. Now 34, married and the father of a 6-year-old daughter (who appears as the youngest of the two daughters belonging to the husband and wife played by Richard Chamberlain and Olivia Hamnett in "The Last Wave") and 2-year-old son, Weir described himself as "already an old-timer" during a recent stopover in Washington. "Most of us have only two or three features to our names," he said, "but the filmmaking climate has imporved so rapidly that it's possible for the directors who began getting recognition only a short time ago to be dismissed as the old guard by people just coming out of film school or short-film production. We're considered a little too slick and potentially disloyal, likely to sell out to the first ofter that comes from Hollywood."

Weir acknowledged that the right sort of offer from Hollywood might be difficult to refuse. "There's certainly a lure here," he said. "I'm fascinated each time I come to this country, and the trips have always been full of tension and expectancy, because you're waiting to meet someone celebrated or influential or you're exposing your films to a new group of people and watching their responses. Something's at stake each time. There's a special glamor about Hollywood: You can't help thinking of it as the capital of the movie business and feeling its khistorical significance. And then there's your huge audience, of course.It wouldn't hurt if some of our movies caught on here.

"Many people cling to a native view of the business. I was reminded of it the other day in New York, I appeared on a call-in show late at night on a cable TV station. It was awfully late. I don't believe more than three people could have been watching at that time of the morning. One caller wanted to know why American films were typically so crass and manipulative and foreign films so pure and artistic. Perhaps it's just as well he'll never set eyes on some of those pure, artistic diectors when they first discover Sunset Strip or the Polo Lounge. They've been known to go into a trance and never come out of it."

Who are Weir's peers in the New Australian Cinema? Weir cited Fred Schepisl (pronounced "skipsee"), Phillip Noyce, Philippe Mora and Bruce Beresford. Other names that frequently insprire or British critics include Ken Hannam, Donald Cromble, Tim Burstall, Joan Lang and Gill Armstrong.

Schepisl has completed two features, "The Devil's Playground," a depiction of life at a Catholic boarding school for boys in the '50s that dominated the Australian film awards in 1976, and "The Chant of Jimmiw Blacksmith," a 1978 entry at Cannes that Pauline Kael recently touted (in the course of a harsh review of "The Last Wave") as "the only great Australian movie I've seen." Noyce's first feature, "Nowsfront," a panoramic account of Australian life in the decade after of rival newsreel cameramen, was well received at the last New York Film Festival. Mora, known for the documentries "Swastika" and "Brother, Can You Spare a Dime?," an elaborate adventure melodrama starring Dennis Hopper as a notorious 19th-century outlaw. Beresford was responsible for "The Adventures of Barry McKenzie," a knockabout comedy which became the first major box-office success among features underwritten by a government film development agency (now called the Australian Film Commission) established in the early '70s.

Hannam's "Sunday Too Far Away," a 1975 feature recreating the conditions that led to a strike among sheep shearers in the '50s, was backed by a regional film commission created in South Australia. This agency, headed by Gil Brealey, whom Weir considers the most enterprising bureaucrat to emerge during the decade, followed through by investing in "Picnic," which became an overwhelming popular and criticazl success in 1976, grossing over $2 million in the first six months of release. According to Weir, the film has now grossed about $5 million and should become the first native production to crack the Top Ten box-of-fice attractions. The country itself has fewer than 900 theaters and a population of less than 14 million.

The successful example of the South Australian Film Commission led to the establishment of similar agencies in Victoria and New South Wales. The country's three principal theater chains began to invest in production. For example, Hoyts, which is owned by 20th Century-Fox, joined the Australian Film Commission and Victorian Film Commission in financing "Jimmie Blacksmith."

Donald Cromble's first feature, "Caddie," a story about a young mother who walks out on her unfaithful husband and tries to support her kids alone during the Depression, was the popular runner-up to "Picnic" in 1976. Tim Burstall is generally regarded as a major talent who stoops to crass vehicles, notably sex farces. Joan Lang is a leading screenwriter who also directed a pair of documentaries, "The Pictures That Moved" and "The Passionate Industry," recalling the pioneering years of Australian filmmaking, which succeumbed to British and American domination with the outbreak of the Depression and took another 40 years to reassert itself. Lang has adapted a famous Australian novel of the Victorian period, "My Brilliant Career," for Gill Armstrong, a 27-year-old woman directing her first feature after winning acclaim for several shorts.

Weir's first short films were comic divertissements made to entertain fellow employes at a Sydney TV station where he was initially hired as a stagehand. "There was all this equipment around," Weir recalled. "I began experimenting, trying to do stuff with a professional look. At the same time I was doing a little acting and writing free-lance reviews for small periodicals. It was a heady period in general. You felt a lot of fervor and excitement, much of it connected with the Vietnam war controversy, which was tearing up our country as much as it was yours.

"I just staried trying my hand at short, often comic little films, I suppose heavily influenced by Richard Lester. Some of them amused people and came to the attention of program directors, who used them as fill-ins on the air. After a couple of years at the station I took a job with the Commonwealth Film Unit, which made documentaries for the government. It's now called Film Australia. While I was there I managed to shoot a short feature on the side, using my own place as the location. It was called 'Homesdale,' a horror comedy set at a sinister country retreat, where both the staff and the guests were a little deranged."

Weir descrmes his upbringing in Sydney as typically, comfortably middleclass. His father was a prosperous real estate agent, and Weir worked for him after dropping out of the University of Sydney in his junior year. He quickly made enough in commissions to finance a trip to Europe in 1965. "Two years later I came back totally changed," he said."I had acquired a wife and a crazzy idea that no career could be more appealing than a career in show biz."

Judging from "The Last Wave" and "Picnic at Hanging Rock," Weir is preoccupied with the concept of civilized, bourgeois patterns of behavior being threatened by intimations of the primitive and irrational. Perhaps the Australian setting gives a distinctive coloration and force to this kind of a apprehension. The geography, history and culture of the country seem to exaggerate the contrasts vetween settled communities and wilderness, European and aboriginal civilizations, modernity and antiquity. Weir and cinematographer Russell Boyd are particularly adept at imagery that expresses such contradictions, juxtaposing civilized characters or settings against natural surroundings or forces of nature that seem capable of engulfing them. This systematically disquieting perception makes one eager to follow their work and catch up with the best work of their compatriots. There's a vision of the world that isn't quite like any other in these movies.

Weir defines it this way: "Everything is built on the real and ordinary, but there's chaos underneath. We try to protect ourselves from the mystery, but it's all around, just waiting to reveal itself and terrorize us. The ironic thing about movies is that you can use this highly sophisticated technology to restore the sense of mystery that an industrialized, urban society tends to obscure. It's a mechanical process with an uncanny power of emotional suggestion. It's fascinating to try to orchestrate images in a way that will affect people emotionally. It's not such a bad way to make a living either."