By Lisa Schwarzbaum
Updated April 16, 1999 at 04:00 AM EDT

Clever idea, employing a campy babe with popping assets as one of the two on-screen humans taking part in this elaborate 3-D novelty act. But in the interests of family-friendliness, Elvira, Mistress of the Dark (Cassandra Peterson), never busts out of the screen. Instead, a hyperactive flying robot called Max, assistant to a hysteria-prone professor (Stuart Pankin, also the voice of Max), explains the history of three-dimensional photography and filmmaking from the 19th century to today. Forget about them; they’re nothing but rib-elbowing vaudevillians, cracking lame, for-the-kiddies jokes while keeping the energy level up for an audience challenged by unwieldy eyewear.

There’s real excitement, though, in this cleverly art-directed trip, complete with roaring dinosaurs, precipitous roller-coaster rides, and plunges deep underground (and underwater). Perspective shifts and mutates; gizmos from the professor’s lab come to life, move around, and resettle. Production values remain high, even when Elvira sings ”Haunted House” for no good reason. Encounters in the Third Dimension doesn’t find a use for 3-D besides celebrating 3-D, but the party’s a pip. B+