Frankie Muniz 'didn't realise how much of a challenge' his latest movie would be

Frankie Muniz "didn't realise how much of a challenge" it would be to make a sci-fi movie.

The 39-year-old actor is mostly known for his roles in comedies but has now switched up genres to play the title role in 'Renner' - which follows a reclusive computer genius who creates an AI to help him find love - but hadn't appreciated how difficult it would be until he arrived for shooting.

He told ScreenRant: "I love the idea of that challenge. Granted, I didn't realise how much of a challenge it would be until I showed up on set.

"I'm really thrilled at how it turned out.""

But the former 'Malcolm in the Middle' star knew as soon as he read the script that he wanted to do the part but "didn't expect" it to pan out the way it did.

He said: "If I'm this excited to read the script, I can't imagine what the movie will be like.

"The movie I thought I was reading on pages one through twenty, versus page twenty to fifty, versus the last thirty pages, I definitely didn't expect it to go there."

The film is directed by Robert Rippberger, who noted that sometimes audiences don't realise just how "hard" it is to be an actor on a set and the whole production is hinged on a "trust fall" between those behind and in front of the camera.

He said: "I think a lot of people also don't appreciate how hard it is to be an actor. I mean, the vulnerability, the amount of pressure. The camera is ultimately looking one place through the whole movie, and it's on Frankie the entire time with this movie. It's a tremendous trust fall between actor and director."