You are forgiven for confusing StreetDance 3D with Step Up 3D or any of the other disenfranchised dancing youth movies.
You are quite right in your assumption that the 3D element is totally unnecessary, and your hunch that the movie probably has a simplistic plot is correct. And what the heck is Charlotte Rampling doing in a film like this?
On the other hand, StreetDance 3D features dance sequences that are absolutely exhilarating, and they are sequences that put dance troupes such as Flawless and Diversity or Britain's Got Talent winner George Sampson in the same frame as classical dancer Richard Winsor. The film, which is directed at a teen audience, is a smash hit in England and will no doubt do similar big box office on this side of the Atlantic.
So here's the answer to that question up above about Charlotte Rampling: Winning herself a vast new audience of young viewers, that's what.
StreetDance 3D concerns a pack of agile kids preparing themselves for the UK Street Dance championships. The competition is stiff, and worse yet, the troupe leader abruptly quits to pursue school and work. Leadership of the dance group falls to Carly (Nichola Burley), and she struggles with her new role. She doesn't have much authority. She forgets to book studio time for practice. Will the troupe fall apart?
One thing Carly desperately needs is rehearsal space, but she has no money for it. One day, delivering sandwiches at her part-time job, Carly stops in at the posh ballet school. Cor blimey, it's all leotards and slow motion, but Carly isn't intimidated. She bucks up and tells Helena (Charlotte Rampling), the woman who runs the ballet school, that she's a dancer too.
Once Helena sees Carly's style of hip-hop dancing for herself, she's convinced the street dancers are just the inspiration the ballet dancers need. The ballet dancers are bored and complacent; Helena thinks one group will motivate the other to do better.
At first, when the street dancers and the bunheads dance together it's all fighting and class distinctions, but eventually, classical and crumping manage to mesh. The story is pure Plots-R-Us, but Carly learns to be a leader, survives betrayal and even gets to fall in love -- so all's well that end's well, etc. When the action flags she also dances a few times in her undies, so it's not as if the appeal of StreetDance 3D is solely in the dancing.
Well, it is, but the cast is adorable and the dancing is gobsmacking.