"The Sensual Man" sounds like the most desperate of titles, and the Italian movie now masquerading under this title at the K-B Fine Arts is, in fact, a pathetic case. Moviegoers who recall Marcello Mastronianni's best dramatic vehicle, "Il Bell Antonio," may detect flickering similarities in "The Sensual Man," which was also derived from a novel by Vitaliano Brancati and stars Giancarlo Giannini as a Sicilian nobleman whose social conditioning points him in the direction of increasing sexual dissipation and emotional wretchedness.

Unfortunately, Marco Vicario proves such a blundering, mawkish director that the tragic resonance of "Bell' Antonio" is replaced by driveling and bewildering sentimentality. Poor Giannini, doing his brooding, photogenic utmost to bring conviction to a character whose potentialities and limitations are never coherently dramatized, is left to turn slowly, slowly in the celluloid wind, a more vivid example of victimization that the protagonist himself.

The movie comes on vulgar and bawdy, with sequences depicting the adolescent sexual experiences of illomened Paolo, whose grandfather is a lustful, boisterous and reprobate and whose father is a melancholy, ineffectual prig. There are perhaps even fewer family resemblances between Lionel Stander, cast as the grandfather, Riccardo Cucciolla, cast as the dreary father, and Giannini, who eventually turns up as Paolo, than there were in the absurb genetic linkage of Burgess Meredith, William Hickey and Peter Fonda in "92 in the Shade."

Nevertheless, one might have overlooked eccentric casting if Vicario had established a source of conflict that was crucial to understanding Paolo's ultimate self-pity and disintegration. One can tell that someone, presumably the original author, had something of the sort in mind, but Vicario's techniques are so crude that both Paolo's role models look alienating and ridiculous from the start. Far from evolving into a tragically vulnerable figure, a man at odds with himself, Paolo suggests a hopeless, self-indulgent dunce, the last rotting branch on an expendable family tree.

The conflict in Mastroianni's Antonio was poignantly clear. Lust and love were so separated in his mind that he found himself impotent with his beloved young bride. Paolo also seems to suffer from this humiliating inhibition, but it emerges so late in the story that one can't feel convinced or sympathetic. The preparation simply wasn't there. From the beginning the clues have been confusing or inconclusive.

For example, what is one to make of Paolo's seduction by the pretty maid (Ornella Muti, who is indeed an irresistible vision of loveliness) who also sleeps with his grandfather? Vicario depicts it as a sublime romance, causing exaggerated outbursts of jealousy from grandpa, only to drop it abruptly as the young lovers are rolling in a mountain of corn kernels. Paolo's later romantic escapades make it seem unlikely that he's haunted by the memory of this adolescent idyll. It's not as if he kept pursuing a lost love only to be confronted time and again with stark lust. The director's inability to portray key episodes clearly and follow through makes it impossible to judge why the protagonist ends up brokenhearted.

Barbara Bach, the Barbie Doll of "The Spy Who Loved Me," appears briefly as one of the objects of Giannini's desire. Giannini and Rossana Podesta also indulge in a pre-coital slugging match that appears to be lifted straight from the uglier scenes in "Swept Away," although "The Sensual Man" bears a copyright date of 1974 and may have put a few ideas in Lina Wertmuller's head, for all one knows. Cucciolla, one of the most uncharismatic actors I've ever seen, has been entrusted with a deathbed oration that lingers on for what seems like severl hours. It's an index to Vicario's obliviousness that he would go all mushy for a character and performer most people would be overjoyed to kiss off.