This past weekend director James Gunn announced that principal production on Marvel Studio's Guardians of the Galaxy has come to and end - but there's still plenty of work that needs to be done. Just like all big, sci-fi blockbusters, the movie is going to need to spend a number of months in post-production so that digital effects artists and editors can put all of the finishing touches on the film and complete it as the director's original vision. What makes the project different from most, however, is that some of the stars still haven't had the chance to film their parts of the movie - which is why we now have the above video featuring Vin Diesel walking around a parking lot on a pair of stilts.The clip was posted to the actor's official Facebook page - a regular source of updates about Diesel's work - and while there's nothing that blatantly labeling this video as being part of Guardians prep, the evidence is there. For starters, even though this video was taken on the set of Fast & Furious 7 , it's titled "Tree Form Down Time," which is obviously a reference to the tree-like character Groot that Diesel is said to be playing in the Marvel movie. What's more, if you turn the volume up all the way up around the :45 second mark (when he's talking to a bunch of people) you can clearly hear him say that he's practicing for his part.While news about Diesel playing Groot is old at this point, the actor confirming his role in the movie back in August, what is significant about this is that it seems to confirm that the star will be doing a bit of motion capture work in order to bring life to the alien. This should be seen as good news for fans of the actor, as the part would have been quite small without a physical contribution. As comic book fans know, Groot only actually ever says one thing - "I am Groot" - so it would have been a real challenge for Diesel to add anything to the character through his voice alone. Walking on stilts and using motion capture will at least allow him to add some physicality.Guardians of the Galaxy won't be arriving in theaters until August 1st, but we couldn't be more exciting for it. In addition to Diesel, the film also stars Chris Pratt (as Star-Lord), Zoe Saldana (as Gamora), Dave Bautista (as Drax the Destroyer), Bradley Cooper (as Rocket Raccoon), Lee Pace (as Ronan the Accuser), Michael Rooker (as Yondu), Karen Gillan (as Nebula), Djimon Hounsou (as Korath), Benicio Del Toro (as The Collector), John C. Reilly (as Rhomann Dey), Glenn Close (as Nova Prime), Peter Serafinowicz and Gregg Henry.