New Delhi: He has played a gangster, a criminal and even an underworld don on screen. Now, as he prepares to be seen as former underworld don Muthappa Rai in Ram Gopal Varma's "Rai", actor Vivek Oberoi says such roles give him a high. However, the actor, who has been appreciated for his negative roles, shared that it was never a conscious decision by him to portray grey characters. Asked what he really likes about such roles, Vivek said: "Essaying gangster roles has always given me a kick and an adrenaline rush that is indescribable." Talking about his characters -- Chandu from "Company" (2002), Maya Dolas from "Shootout at Lokhandwala" (2007) and Pratap Ravi from "Rakht Charitra" (2010), the 39-year-old actor said that "all these characters were so layered." Vivek also enjoys versatility -- sometimes as a loverboy in a film like "Saathiya" and sometimes in comic capers like "Masti". But he says he has been especially lauded whenever he has played grey characters. "It was never really a conscious decision to only portray grey characters. I enjoy doing versatile roles. However, the kind of response and reactions that I received for my gangster roles, have been phenomenal," said the son of veteran actor Suresh Oberoi. "I have played a gangster in three blockbusters and my fans enjoy watching me essay these roles. And to me that is the greatest testimony," he added. In almost 15 years since his debut, Vivek has played an array of characters from romantic, comedy, negative and action films like "Saathiya", "Kisna", "Masti", "Mission Istaanbul", "Yuva" and "Omkara". Last seen on screen in 2013 along with actors Hrithik Roshan, Priyanka Chopra and Kangana Ranaut in "Krrish 3", is now looking forward to his part in "Rai", which is inspired by a real life character. How is he preparing for the title role? "Apart from working on the look, my physique and the finer nuances of the character, I have also met with people who knew Muthappa Rai closely. At the moment, that is all we can reveal," added the "Prince" actor. Vivek added that "there is a lot of homework that is going into this role". The "Zila Ghaziabad" star says the story for "Rai" will be told in an interesting and an entertaining manner. At a time when slice-of-life films and biopics on national heroes and icons are doing so well, what made him go for "Rai"? Vivek said: "The film is based on the life of Muthappa Rai, a former underworld don from South India who went on to become an entrepreneur. It is an interesting story told in the most entertaining manner. It will definitely break the clutter." Filmmaker Ram Gopal Varma's films have mostly revolved around negative characters, and Vivek has been part of some of those projects. Does he think the perception of anti-heroes in Bollywood needs a much-needed change now? "It definitely does, and I think we are on our way to getting there. My character Kaal from 'Krrish 3' did receive a lot of great feedback. People welcomed the kind of mileage an anti-hero got in the film," he said. Ultimately, Vivek feels scripts are the "biggest and only hero" for films.