Ang Lee is nothing if not an ambitious filmmaker and he follows up his 3-D “Life of Pi,” with an expansive Iraq War epic shot in 3-D, in a record-high frame rate, structured as a journey into a heroic soldier’s memory and conscience.

Oh, and “Billy Lynn’s Long Halftime Walk” includes the enormous pageant of a professional football game, complete with a Destiny’s Child halftime show, an intense battle sequence and a cast that runs the gamut from Kristen Stewart to Steve Martin; from Vin Diesel to Chris Tucker.

The movie, which this critic screened in 2-D and at a normal 24 frames per second projection rate, is every bit as crazy as it sounds.

It captures a vulgar Americanism quite well, in the empty platitudes accorded Spc. Billy Lynn (Joe Alwyn) for his heroism, the uneasy blending of patriotism and commerce that defines major sporting events in this country, and the eager exploitation of these soldiers by parties seeking personal gain.

And yet it is also a spectacular mess — thoroughly uneven in its plotting, filled with character touches that aggressively strain credulity and performances that sacrifice naturalism and authenticity in favor of an abiding artifice.

The picture follows Lynn and his squad as they are brought to a stadium that strongly resembles the Dallas Cowboys’ behemoth, to participate in the aforementioned propagandistic halftime performance, complete with dozens of synchronized dancers, explosive pyrotechnics and other recognizable touches. The movie is structured according to the whims of Lynn’s traumatized mind, as it jumps back to his experiences in Iraq throughout the process.

Alwyn is a giant blank at the center of the picture, and Lee is so committed to aggressively pounding home his messages that the movie drags through interminable sanctimonious conversations and injects forced dramatic layers into a story that’s sufficiently engaging in its most basic form.