<P> In early April 2013, Zoe Saldana entered into negotiations to star as Gamora in the film, and it was confirmed she had been cast later that month . Also in April, Michael Rooker joined the film's cast as Yondu, and it was announced that Ophelia Lovibond had been cast in a supporting role . By this point in time, Lee Pace was in final negotiations to play the villain of the film . In May, Marvel offered John C. Reilly the role of Rhomann Dey . At the same time, it was disclosed that filmmakers were looking at actors including Hugh Laurie, Alan Rickman, and Ken Watanabe, for another role, and that Christopher Markus and Stephen McFeely were providing finishing touches to the script . A few days later, Glenn Close was cast as the head of the Nova Corps in the film, followed shortly by the casting of Karen Gillan as the film's lead female villain . By June 2013, Benicio del Toro was cast in the film, as part of a multi-film deal with Marvel Studios . Later in the month, it was confirmed that Reilly had been cast as Rhomann Dey . </P> <P> Special effects makeup designer David White took head and body casts of actors, such as Bautista, to experiment with materials used to create the characters . White said, "James always pushed for practical and makeup effects . He wanted, like me, to see the real deal there on set ." White was careful not to use "modern" creature designs to ensure they did not fall short in Gunn's uniquely envisioned world . White and his team created upwards of 1,000 prosthetic makeup applications and 2,000 molds of different - colored aliens . For the specific aesthetic look to the film, Gunn wanted to create "a colorful science - fiction world", and include elements of 1950s and' 60s pulp movies, citing the Ravagers' spaceships, which he compared to muscle cars, as an example of the latter . Science fiction artist Chris Foss inspired and helped design the final look of some of the spacecrafts that appear in the film . </P> <P> Principal photography began around July 6, 2013 in London, United Kingdom, under the working title of Full Tilt . Filming took place at Shepperton Studios and Longcross Studios . Later in July, Gunn and the film's cast flew from London to attend San Diego Comic - Con International, where it was revealed that Pace would play Ronan the Accuser, Gillan would be Nebula, del Toro as The Collector, and that Djimon Hounsou had been cast as Korath . Close was later revealed to play Nova Prime Irani Rael . Also at San Diego Comic - Con, Feige stated that Thanos would be a part of the film as the "mastermind". On August 11, 2013, filming began at London's Millennium Bridge, which was selected as a double for Xandar . In August 2013, Marvel announced that Bradley Cooper would voice Rocket . On September 3, 2013, Gunn said that filming was "a little over half (way)" complete . Also in September, Vin Diesel stated that he was voicing Groot . However, Marvel did not confirm Diesel's involvement in the film at the time . On October 12, 2013, Gunn announced on social media that filming had completed . </P> <P> Director of photography Ben Davis used Arri Alexa XT cameras for the film, saying, "I'm traditionally a photochemical fan, but going with the digital format was the right way for this movie...the Alexa (provided) the right look for this particular film ." During the opening scenes in the 1980s, Davis chose JDC Cooke Xtal (Crystal) Express anamorphic prime lenses because they "had more anamorphic artifacts and aberrations, which (he) felt added something ." Davis used spherical Panavision Primos for the rest of the film . Additionally, Davis worked closely with production designer Charles Wood in order to achieve the correct lighting looks for each scene . Dealing with two fully CGI characters forced Davis to shoot scenes multiple times, usually once with the references for the characters and once without them in the shot . </P>

When did they start filming guardians of the galaxy