What with elements of eroticism, mysticism, hedonism and exoticism, Barbet Shcroeder's "The Valley," now at the K-B Cerberus, is certainly a portentous curiosity.

Shot in 1972 during a six-month sojourn in Papua New Guinea, "The Valley" was no doubt a great filmmaking adventure for Schroeder and his company. Unfortunately, the experience is diminished at this end by trite fictionalization. The threadbare plot and characters contrived by Schroeder fall particularly short of scenic and anthropological fascination of the setting. Ultimately, the picture seems a vainly pretentious travelogue, a "Lost Horizon" for die-hard hippies that expires on a note of enigmatic hokum.

Schroeder probably squandered a sure chance of commercial success by declining to load up on tropical eroticism. The heroine has obvious affinities with all the sexually liberated Sleeping Beauty figures from Lady Chatterly through Emanuelle. Called Viviane and played by Bulle Ogier, she's identified as the wife of a French diplomat stationed in Australia. At a trading post on Papua, she takes a fancy to a lanky young guide, Oliver (Michael Gothard, one of Vanessa Redgrave's torturers in "The Devils").In fact, Viviane is so symbolically flustered that she drops a ceremonial dagger on his foot. Not one to hold a grudge, Olivier invites her back to his tent to see his stash of Bird of Paradise feathers. Viviane ends up sharing his cot that evening. The morning after she decides to join the small group of Europeans Olivier plans to escort into the mountains in search of a legendary valley.

Intially, Viviane rationalizes going along only as far as a missionary outpost where Olivier has hinted that feathers might be acquired. Charmed by her new promiscuous companions and by encounters with genial Mapuga tribesmen, who include the visitors in their colorful feasts and dances, Viviane shucks off the bourgeois conditioning, and becomes a convert to visionary sensuality. She also becomes the third obliging member of a harem.

The harem setup looks pretty sultry, and it might have played that way too if Schroeder were an impassioned director, even an impassioned screwball director in the manner of Ken Russell or John Boorman. A curious tease, Schroeder tends to retreat to a position of deflating emotional detachment after toying with deliberately provocative, sordid notions. "The Valley" fizzles in the same way that his other fictional features fizzled: the drug addicition (on Ibiza yet) story "More" and the sadomasochism story "Maitresse." All are romances about obsessive passion compromised by Schroeder's inability to identify intimately with characters driven to obsessive extremes. Schroeder seems to have exactly the wrong temperament for over-heated material.

The direction is often slack enough to make you cringe. The opening sequence at the trading post is so awkward that the entire film unfolds under a cloud of klunkiness. Despite the inherent sexual tension, the story is so carelessly formulated that it comes as a total surprise when Olivier is given a long speech expressing astute skepticism about the expedition moments before the denouncement. One gathers that Viviane's new lovers were supposed to represent conflicting outlooks, but it won't do to begin a philosophical debate on sexual rivalry so late in the story. At this stage all it can amount to is a disillusioning afterthought.

It's not difficult to understand how Shcroeder might have derived satisfaction from a project like "The Valley." It's just that the public must be content with a less broadening experience from a less privileged perspective.