"Star Trek: The Motion Picture," Paramount's $45-million testimonial to the fans of its erstwhile TV series, passed its initial public test at a world premiere showing last night at the K-B MacArthur.

Of course, a generally warm reception has to be expected from an invitational audience with every reason to wish the movie well: the principal filmmakers, Paramount executives, and members of the National Space Club, whose educational program will be enriched by the proceeds from the evening.

A certain amount of bet-hedging in opening remarks prior to the showing betrayed the fact that "Star Trek" had even well-wishers a trifle concerned. John Lent, president of the National Space Club, prefaced his welcome to the audience by saying, "Now I've not seen the film we're about to enjoy."

Co-star William Shatner, one of several original cast members who appears in the movie, introduced the "Star Trek" contingent from the auditorium. In paying tribute to special-effects director Douglas Trumbull and special-effects supervisor John Dykstra, he referred to them as "the geniuses who gave it its epic quality . . . I've heard so much about."

The nervous laughter from the Paramount section seemed to confirm the advance impression that this costly enterprise ultimately depended on the artistry of the special effects team. Brought in late to salvage the effects, Trumbull, Dykstra and their associates appear to have pulled the company's chestnuts out of the fire.

The exposition could be easily disposed of in the running time of a "Star Trek" TV episode. In fact, a good deal of the plot was used before. The effects work accounts for a lot of screen time and adds the necessary pictorial class and elaboration to what would otherwise be exposed as a one-hour teleplay projected on a big screen.

White the effects artists give "Star Trek" an impressive scenic aspect, they're unable to spruce up the stale character relationships or pick up the stroytelling pace, which is never more than half a step ahead of the tedious, Devotees of the series may be willing to overlook the dragginess for old times' sake, but the lack of dynamic physical action or characters who can function as surrogates for children left doubts about the movie's appeal with both non-devotees and uninitiated juveniles.

Unlike "Star Wars," which transposed like action-movie style to a science-fiction setting "Star Trek" resembles a traditional whodunit in outer space. The crew of the Starship Enterprise can't outfight an alien adversary, but they can outwit and appease it, a process perhaps more appealing to homely philosophers like producer Gene Roddenberry than kids inclined to identify with direct-action types like Han Solo and R2-D2.

"Star Trek: The Motion Picture" is neither triumph nor fiasco. At worst it's diverting, harmless hokum, at best an attractive, if attenuated, showcase for our best special-effects specialists. All in all, the most presentable passive entertainment that$45 million could probably buy.