On the evidence of “Outside Providence” and their newest effort, the Farrelly brothers, masters of the sophomoric gross-out farce, are mellowing a bit. The maturation process is far from consistent–after all, they had a hand in two of this year’s most disreputable specimens of their preferred genre, “Say It Isn’t So” (which was directed by a protégé) and the half-animated “Osmosis Jones”–nor is it at all complete. But while the Farrellys’ pictures have always mixed sweetness with grotesquerie to some degree, in “Shallow Hal” the proportion has shifted appreciably from the latter to the former. Whether the change is for the better or doesn’t go far enough will up to the individual viewer to decide; some will wish the picture were as hilariously tasteless as “Kingpin” or “There’s Something About Mary,” while others will still squirm at the remaining level of raunchiness. (Whatever your opinion, you’ll probably find “Hal” superior to “Me, Myself and Irene,” in which neither part of the combination worked.) What’s not debatable is that they still haven’t gotten the recipe quite right: the picture is an uneasy blend of the naughty and the nice in which the two ingredients fail to mesh.

“Shallow Hal” is a one-joke film about the title character, a guy who judges people–especially women–by appearance alone; for him, the only beauty is of the skin-deep kind. Hal, however, is no Lothario; a rather goofy-looking guy himself, he always pitches himself to gorgeous gals and winds up rejected. (The same can be said of his equally shallow friend, Mauricio.) One day, though, he’s cooped up in a stalled elevator with self-help guru and TV pitchman Tony Robbins, who hypnotizes him into seeing the beauty inside people instead of their mere exterior. Hal soon falls for Rosemary, an obese girl whom he takes for a svelte, though oddly shy knockout. As Mauricio looks on in amazement and disgust, Hal falls for Rosemary, who turns out also to be the daughter of his billionaire boss Steve Shanahan; needless to say, he soon moves up the corporate ladder, too. A crisis occurs when Mauricio persuades Robbins to end the trance and Hal has to come to terms with his feelings for the real her.

It’s easy to see why the Farrellys were attracted to this concept, cooked up by first-timer scripter Sean Moynihan and then reworked by them. It allows for plenty of coarse comedy as Rosemary scarfs down foods that, to Hal’s eye, never add to her weight, or periodically causes furniture to collapse beneath her (inexplicably, to him). The best-pal figure of Mauricio also gives ample opportunity for the type of locker-room wisecracking that young male viewers will easily respond to. And yet the transformation of the final reels, in which Hal learns to look beneath the surface to gauge a person’s worth, is bound to appeal to the rest of the audience’s desire to ooh and ah over the idea of romance fulfilled. And, of course, there’s a last-minute obstacle to be overcome before the obviously-foreordained finale.

In terms of basic narrative, therefore, “Shallow Hal” is cannily constructed. But there are problems. The entire Robbins-hypnosis explanatory device is both old-hat and crudely promotional. And the basic premise is never worked out: Hal’s new perception appears to be entirely selective, involving some of the people he bumps into but not others. (Why doesn’t Mauricio change appearance, for instance, or Mr. Shanahan–while Mrs. Shanahan and a bevy of burn-scarred children are transformed? And what’s the story with Nurse Tanya Peel, who originally appears as a wicked old crone but for some reason later looks beautiful–is it just the different context?) And in too many instances the filmmakers go for the easy shot so familiar from their past pictures. The initial hospital scene, for example, in which Hal’s dying, drug- addled father–a preacher, no less–gives his son, in none-too-refined language, some advice about women is a cheap shock; and the brothers can’t resist the big gross-out moment near the close so characteristic of their style (the chicken-in-the-derriere of “Irene,” the hand-in-the-cow’s rump of “Say”). In this case, it’s not quite so obnoxious as those, but it easily could have been handled with a reaction shot instead of an explicit special-effects gag that seems designed merely to extract a moan from the audience. Throughout, moreover, the Farrellys’ technical skill remains rudimentary at best. One might hope that they would have learned something by now about camera placement, timing and how to build a scene, but that appears not to be the case.

Some of the casting doesn’t quite work, either. As Hal, Jack Black is the archetypal second banana unwisely promoted to the romantic lead. Black was great in smaller parts in “High Fidelity” and “Jesus’ Son,” but in a role that keeps him in front of us for nearly two full hours, his awkwardness and bug-eyed intensity grow more than a trifle tedious. Gwyneth Paltrow proves a really good sport as Rosemary, happily donning the same sort of fat suit that Eddie Murphy, Matthew Lawrence and Julia Roberts have worn with considerable success in recent films (talk about a trend!) and willingly showing more skin than she’s ever done before. (One might have expected her to be more ready to do so earlier in her career, but she’s obviously not past her prime.) Jason Alexander does his “Seinfeld” shtick as Mauricio; he’s funny, in the usual crude way, but one suspects that he’s capable of wider range than he’s yet had an opportunity to explore. Rene Kirby, who suffers from spina bifida, is very ingratiating as Hal’s buddy Walt, and you have to give Joe Viterelli, as Mr. Shanahan, credit for being willing to play so strongly against type (he’s ordinarily the Mafia thug, after all) by doing the role in a thick Irish brogue. He manages, though it’s never entirely convincing.

That’s something one might say of “Shallow Hal,” too. It attempts to take the Farrellys into different, sweeter territory, but the penchant for the gross-out gag, as Michael Corleone would say, keeps pulling them back in. The result isn’t bad; it’s just not good enough.