As One Direction gear up for the filming of their 3D movie, the boys have been busy with rehearsals in London along with their backing band as they put the final touches on their live show in preparation for two Japan concerts this weekend.

Billboard reports the rehearsals began last week as the last prep for 1D's performances on Jan. 18-19 in Tokyo, which will be filmed in 3D by director Morgan Spurlock of 'Super Size Me' fame. Similar to Katy Perry's 'Part of Me,' the movie will include concert footage and behind-the-scenes glimpses of the world's hottest boy band.

charitable appearance for Comic Relief. Last week, Niall Horan tweeted some details from the practice sessions:

Co-producer Simon Cowell said, "I'm delighted we're making this film and Morgan is the perfect person to give that access-all-areas, behind-the-scenes look into what it's like to be One Direction today. What the band have achieved is incredible, they and their fans have made history around the world -- this is for them."

The 3D film is expected to arrive in theaters on Aug. 30, just after the guys finish up the summer North American leg of their world tour. The boys will be touring almost non-stop this year from February to the end of October, wrapping up their tour in Australia.

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