Mumbai, Sep 22 : Actress Rakul Preet Singh, who was recently seen in the Nikhil Mahajan-directorial 'I Love You', has spoken about her upcoming sci-fi film 'Ayalaan', which she went on to call a 'once in a lifetime experience'. 'Ayalaan', which is directed by Tamil filmmaker R. Ravi Kumar is a sci-fi-extraterrestrial-comedy film which employs a great deal of VFX and high-quality CGI. While using CGI in Indian films is nothing new, having a movie with more than 4,500 CGI shots is a new one. Talking about the film, the actress said: "Oh, it was a once-in-a-lifetime experience. Because there is an extraterrestrial in the picture, and you know there isn't one when you're shooting, but you're assuming there is. You must shoot it in such a way that people believe the film has an actual alien." "You're reacting to a prop, you're reacting to nothing, and you have to do it convincingly. You must learn to stay on your mark and not deviate since they will use CGI to fill in the gaps around you. So that was a truly unique experience for me, and I thoroughly enjoyed it." 'Ayalaan' is creating quite a buzz, not just for its compelling storyline but also for the groundbreaking use of CGI. The story itself has a similar line to Rakesh Roshan's Bollywood film 'Koi Mil Gaya', which also saw an alien being trapped on earth. The Tamil film also sees a similar plot only this time instead of a costume, much of the movie is shot on a green screen while featuring a lot of high-quality VFX, along with a different take as the alien does manage to go home, though this only brews more trouble. Directed and written by R. Ravi Kumar, the movie stars Sivakarthikeyan, Rakul Preet Singh, Karunakaran, Sharad Kelkar, Yogi Babu, Isha Koppikar, Bhanupriya and Bala Saravanan. /IANS