Robert Downey Jr. struggled with the technological demands needed for 'Gravity'.
The 48-year-old actor was initially cast in the award-winning space odyssey - which stars Sandra Bullock and George Clooney - but had to step down after he didn't have the space needed to "breathe" and "improvise".
Director Alfonso Cuaron told The Hollywood Reporter: "It became very clear that, as we started to nail the technology, or narrow the technology, that was going to be a big obstacle for his performance.
"I think Robert is fantastic if you give him the freedom to completely breathe and improvise and change stuff. [But] we tried one of these technologies and it was not compatible. And, after that, we [had a] week that we pretended as if nothing was happening and then we talked and said, 'This is not going to work. This is tough.'"
It was not until Warner Bros. gave the film the go-ahead that Cuaron began casting talks.
He added: "It was not until some elements came into place that we could responsibly go to the studio and say, 'We can set a start date.
"Then you can do offers, and that is when we went after Sandra [Bullock] and George [Clooney]."
'Gravity' has 10 nominations at the 86th Academy Awards nominees including Best Picture, Best Director and Best Actress and the film was also awarded six BAFTA Awards, including Outstanding British Film and Best Director.
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